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Introduction to Elements

Democritus was the first to suggest the idea of the atom - the idea that something can represent the smallest possible particle of matter. However, he did not know what these atoms were.  He believed that they were indestructible.  Also, he believed there had to be a vast number of these atoms with a handful of different shapes: smooth, rough, cubical, etc. These shapes, he believed, accounted for the different physical properties of matter. For example, he hypothesized that when several rough atoms stuck together the result was a solid- something impossible to tear apart. When several smooth atoms came together they would slide past one another and result in a liquid. He believed that there were also smooth atoms that were light as well, this property of lightness gave them an ability to float- explaining gases. Combining different atoms, Democritus concluded, resulted in everything in our world (7).


Although Democritus ideas were noteworthy, they were incorrect. Despite this, is should be recognized that his ideas started the foundation for how we think about our world, and what makes up our world. In time, the ideas of Democritus were forgotten and the ideas of the famous philosopher, Aristotle, took center stage. Aristotle proposed that the world was made entirely up of four qualities: hot, cold, wet, and dry. He speculated that the everything in the world was made up of differing combinations of these qualities. For example, water was cold and wet and fire was hot and dry. Contradictory to Democritus proposal that slippery, smooth, atoms accounted for water’s wet properties Aristotle argued that its property could be attributed to its quality of “wetness.” Aristotle wrote on a myriad of subjects and although a much of his writing makes little sense today, his word was accepted without hesitation at the time (5).

 chem for real.jpg

Finally, in the 17th century a philosophy teacher by the name of Pierre Gassendi challenged Aristotle’s ideas. Gassendi did not think Aristotle’s idea of four qualities made sense. This prompted Gassedi to set out and disprove Aristotle’s ideas with research and induction. Gassendi, after much observation and experimentation, formulated his own theory. Instead of atoms having different shapes, like Democritus propsed, Gassendi believed that they were all fairly alike. Originally Gassendi believed atoms were little balls with hooks- and these hooks, he believed, could interconnect to allow atoms to stick together. Later, however, Gassendi proposed that there was a force, like a magnetic force, that caused the atoms to stick together. This view is similar to, but not the same as, what scientists today believe to be truth (8).

Upon reading Gassendi's published work, Issac Newton became an avid believer in the existence of atoms.  He wrote, “It seems probable to me that God in the Beginning form’s Matter in solid, massy, hard, impenetrable, moveable, particles, of such Sizes and Figures, and with such other Properties, and in such Proportion to space, as most conduced to the End for which He form’d them; and that these primitive Particles being Solids, are incomparably harder then any porous Bodies compounded of them; even so very hard as never to wear or break in pieces, no ordinary Power being able to divide what God Himself made one in the First Creation” (5).

The next figure to come into play was Robert Boyle, an English scientist. Because of Robert Boyle, Aristotle’s idea of four “element” was eliminated entirely. In Boyle’s publication of The Sceptical Chymist​, he criticized all previous philosophers (especially Aristotle). His critics evolved from the previous assumption that gold could be made from metals like iron or lead. Boyle proposed that gold could not be made. He said that it was an “element.” By calling it and element he meant that it was a fundamental substance that did not have the ability to be created by combination of other elements. Along with gold, Boyle believed that silver, mercury, and copper were all elements as well (9). Boyle was one of the first to use the word element and in 1661 he wrote, “ I mean my element certain Primitive and Simple or perfectly intermingled bodies; which not being made of any other bodies, or of one another, are the Ingredients of which all those call’d perfectly mixt Bodies are immediately compounded, and into which are ultimately resolved” (6). Here, he described an element as a fundamental substance and explained that the different types of matter are composed of combinations of these elements. The idea of the element had been born!

Elements: Basic Information


{C} {C}

Name Atomic Number Elemental Symbol Atomic Mass  Classification
Hydrogen 1 H 1.00794 amu Non-Metal
Helium 2 He 4.002602 amu Nobel Gas
Lithium 3 Li 6.941 amu Alkali Metal
Beryllium 4 Be 9.012182 amu Alkaline Earth
Boron 5 B 10.811 amu Metalloid
Carbon 6 C 12.0107 amu Non-Metal
Nitrogen 7 N 14.00674 amu Non-Metal
Oxygen 8 O 15.9994 amu Non-Metal
Fluorine 9 F 18.9984 amu Halogen
Neon 10 Ne 20.1797 amu Nobel Gas
Sodium 11 Na 22.98977 amu Alkali Metal
Magnesium 12 Mg 24.305 amu Alkaline Earth
Aluminum 13 Al 26.9815 amu Other Metal
Silicon 14 Si 28.0855 amu Metalloid
Phosphorus 15 P 30.97376 amu Non-Metal
Sulfur 16 S 32.066 amu Non-Metal
Chlorine 17 Cl 35.4527 amu Halogen
Argon 18 Ar 39.948 amu Nobel Gas
Potassium 19 K 39.0983 amu Alkali Metal
Calcium 20 Ca 40.078 amu Alkaline Earth
Scandium 21 Sc 44.95591 amu Transition Metal
Titanium 22 Ti 47.867 amu Transition Metal
Vanadium 23 V 50.9415 amu Transition Metal
Chromium 24 Cr 51.9961 amu Transition Metal
Manganese 25 Mn 54.938 amu Transition Metal
Iron 26 Fe 55.845 amu Transition Metal
Cobalt 27 Co 58.9332 amu Transition Metal
Nickel 28 Ni 58.6934 amu Transition Metal
Copper 29 Cu 63.546 amu Transition Metal
Zinc 30 Zn 64.39 amu Transition Metal
Gallium 31 Ga 69.723 amu Other Metal
Germanium 32 Ge 72.61 amu Metalloid
Arsenic 33 As 74.9216 amu Metalloid
Selenium 34 Se 78.96 amu Non-Metal
Bromine 35 Br 79.904 amu Halogen
Krypton 36 Kr 83.8 amu Nobel Gas
Rubidium 37 Rb 85.4678 amu Alkali Metal
Strontium 38 Sr 87.62 amu Alkaline Earth
Yttrium 39 Y 88.90585 amu Transition Metal
Zirconium 40 Zr 91.224 amu Transition Metal
Niobium 41 Nb 92.90638 amu Transition Metal
Molybdenum 42 Mo 95.94 amu Transition Metal
Technetium 43 Tc 98.o amu Transition Metal
Ruthenium 44 Ru 101.97 amu Transition Metal
Rhodium 45 Rh 102.9055 amu Transition Metal
Palladium 46 Pd 106.42 amu Transition Metal
Siler 47 Ag 107.8682 amu Transition Metal
Cadmium 48 Cd 112.41 amu Transition Metal
Indium 49 In 114.818 amu Other Metal
Tin 50 Sn 118.71 amu Other Metal
Antimony 51 Sb 121.76 amu Metalloid
Tellurium 52 Te 127.6 amu Metalloid
Iodine 53 I 126. 90447 amu Halogen
Xenon 54 Xe 131.29 amu Nobel Gas
Cesium 55 Cs 132.90546 amu Alkali Metal
Barium 56 Ba 137.327 amu Alkaline Earth
Lanthanum 57 La 138.9055 amu Rare Earth
Cerium 58 Ce 140.116 amu Rare Earth
Praseodymium 59 Pr 140.90765 amu Rare Earth
Neodymium 60 Nd 144.24 amu Rare Earth
Promethium 61 Pm 145.0 amu Rare Earth
Samarium 62 Sm 150.36 amu Rare Earth
Europium 63 Eu 151.964 amu Rare Earth
Gadolinium 64 Gd 157.25 amu Rare Earth
Terbium 65 Tb 158.92534 amu Rare Earth
Dysprosium 66 Dy 162.5 amu Rare Earth
Holmium 67 Ho 164.93031 amu Rare Earth
Erbium 68 Er 167.26 amu Rare Earth
Thulium 69 Tm 168.9342 amu Rare Earth
Ytterbium 70 Yb 173.04 amu Rare Earth
Lutetium 71 Lu 174.967 amu Rare Earth
Hafnium 72 Hf 178.49 amu Transition Metal
Tantalum 73 Ta 180.9479 amu Transition Metal
Tungsten 74 W 183.84 amu Transition Metal
Rhenium 75 Re 186.207 amu Transition Metal
Osmium 76 Os 190.23 amu Transition Metal
Iridium 77 Ir 192.27 amu Transition Metal
Platinum 78 Pt 195.078 amu Transition Metal
Gold 79 Au 196.96655 amu Transition Metal
Mercury 80 Hg 200.59 amu Transition Metal
Thallium 81 Tl 204.3833 amu Other Metal
Lead 82 Pb 207.2 amu Other Metal
Bismuth 83 Bi 208.98038 amu Other Metal
Polonium 84 Po 209.0 amu Metalloid
Astatine 85 At 210.0 amu Halogen
Radon 86 Rn 222.0 amu Nobel Gas
Francium 87 Fr 223.0 amu Alkali Metal
Radium 88 Ra 226.0 amu Alkaline Earth
Actinium 89 Ac 227.0 amu Rare Earth
Thorium 90 Th 232.0831 amu Rare Earth
Protactinium 91 Pa 231.03587 amu Rare Earth
Uranium 92 U 238.0289 amu Rare Earth
Neptunium 93 Np 237.0 amu Rare Earth
Plutonium 94 Pu 244.0 amu Rare Earth
Americium 95 Am 243.0 amu Rare Earth
Curium 96 Cm 247.0 amu Rare Earth
Berkelium 97 Bk 247.0 amu Rare Earth
Californium 98 Cf 251.0 amu Rare Earth
Einsteinium 99 Es 252.0 amu Rare Earth
Fermium 100 Fm 257.0 amu Rare Earth
Mendelevium 101 Md 258.0 amu Rare Earth
Nobelium 102 No 259.0 amu Rare Earth
Lawrencium 103 Lr 262.0 amu Rare Earth
Rutherfordium 104 Rf 261.0 amu Transition Metal
Dubnium 105 Db 262.0 amu Transition Metal
Seaborgium 106 Sg 263.0 amu Transition Metal
Bohrium 107 Bh 262.0 amu Transition Metal
Hassium 108 Hs 265.0 amu Transition Metal
Meitnerium 109 Mt 266.0 amu Transition Metal
Ununnilium 110 Uun 269.0 amu Transition Metal
Unununium 111 Uuu 272.0 amu Transition Metal
Ununbium 112 Uub 277.0 amu Transition Metal

Classifications of Elements: 


  • These elements are found in groups 13-18 of the periodic table.
  • They are not able to conduct electricity or heat well.
  • The solid form of these elements are very brittle compared to metals.
  • These elements are not ductile (can not be rolled into wires or pounded into sheets).
  • They are not lusterous (shiny) and do not reflect light, instead they scatter it.
  • They usually exist as molecules in their elemental form.
  • They are generally gases at room temperature. A few (ex. Carbon) are solids and Bromine is a liquid.
  • They generally form negative ions.
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18
H                                 He
Li Be                     B C N O F Ne
Na Mg                     Al Si P S Cl Ar
K Ca Sc Ti V Cr Mn Fe Co Ni Cu Zn Ga Ge As Se Br Kr
 Rb  Sr  Y  Zr  Nb  Mo  Tc  Ru  Rh  Pd  Ag  Cd  In  Sn  Sb  Te  I  Xe
 Cs  Ba  La  Hf  Ta  W  Re  Os  Ir  Pt  Au  Hg  Tl  Pb  Bi  Po  At  Rn
 Fr  ra  Ac  Rf  Db  Sg  Bh  Hs  Mt  Uuu Uub      Uuq    Uuh    Uuo
     Ce  Pr  Nd  Pm  Sm  Eu  Gd Tb  Dy Ho Er Tm  Yb  Lu    
     Th  Pa  U  Np  Pu  Am  Cm  Bk  Cf  Es  Fm  Md  No  Lr    



Noble Gas:

  • These elements are found in group 18 of the periodic table
  • Group 18 are nobles gases, a subset of non-metals.
  • There are 6 noble gases: Helium (He), Neon (Ne), Argon (Ar), Krypton (Kr), Xenon (Xe) and Radon (Rn).
  • They have an oxidation state of 0.
  • This oxidation state of 0 prevents them from forming compounds readily.
  • They have the maximum number of electron in their outer shell (Helium has 2 where as the others have 8).
  • Because their outer shell of electrons is full they are stable elements.
  • They have high ionization energies.
  • They have very low electronegativities.
  • They have very low boiling points (all are gases at room temperature).
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18
H                                 He
Li Be                     B C N O F Ne
Na Mg                     Al Si P S Cl Ar
K Ca Sc Ti V Cr Mn Fe Co Ni Cu Zn Ga Ge As Se Br Kr
 Rb  Sr  Y  Zr  Nb  Mo  Tc  Ru  Rh  Pd  Ag  Cd  In  Sn  Sb  Te  I  Xe
 Cs  Ba  La  Hf  Ta  W  Re  Os  Ir  Pt  Au  Hg  Tl  Pb  Bi  Po  At  Rn
 Fr Ra  Ac  Rf  Db  Sg  Bh  Hs  Mt  Uuu Uub      Uuq    Uuh    Uuo
     Ce  Pr  Nd  Pm  Sm  Eu  Gd Tb  Dy Ho Er Tm  Yb  Lu    
     Th  Pa  U  Np  Pu  Am  Cm  Bk  Cf  Es  Fm  Md  No  Lr    


noble gases

Example Noble Gas:Ne.jpg


Alkali Metal:

  • These elements are located in group 1 of the periodic table
  • They are very reactive elements
  • Because they are so reactive they do not occur freely in nature
  • These elements have only one electron in their outer shell
  • They are ready to loss their single electron in ionic bonding with other elements
  • Like all metals they are malleable, ductile, and good conductors of electricity
  • These metals tend to be softer then most other metals
  • Cesium and Francium are the most reactive Alkali Metals
  • Exposure to water can result in an explosion
  • They have lower densities than other metals.
  • They have one loosely bound electron.
  • They have low ionization energies and low electronegativities.


1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18
H                                 He
Li Be                     B C N O F Ne
Na Mg                     Al Si P S Cl Ar
K Ca Sc Ti V Cr Mn Fe Co Ni Cu Zn Ga Ge As Se Br Kr
 Rb  Sr  Y  Zr  Nb  Mo  Tc  Ru  Rh  Pd  Ag  Cd  In  Sn  Sb  Te  I  Xe
 Cs  Ba  La  Hf  Ta  W  Re  Os  Ir  Pt  Au  Hg  Tl  Pb  Bi  Po  At  Rn
 Fr Ra  Ac  Rf  Db  Sg  Bh  Hs  Mt  Ds Rg      Uuq        
     Ce  Pr  Nd  Pm  Sm  Eu  Gd Tb  Dy Ho Er Tm  Yb  Lu    
     Th  Pa  U  Np  Pu  Am  Cm  Bk  Cf  Es  Fm  Md  No  Lr    


noble gases


Alkali Metals



Example Alkali Metal:Na (1).jpg


Alkaline Earth:

  • These elements are found in the second group of the periodic table
  • They are metallic
  • They have a oxidation number of +2
  • Having an oxidation number of +2 makes these elements very reactive
  • They are not found free in nature because of their reactivity 
  • They are present in the earth's crust but not in their basic form.
  • They have high boiling and melting points.
  • They have low density, electron affinity, and electronegativity.
  • They react easily with halogens and water.
  • They are softer and stronger than other metals (except the alkali metals).


1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18
H                                 He
Li Be                     B C N O F Ne
Na Mg                     Al Si P S Cl Ar
K Ca Sc Ti V Cr Mn Fe Co Ni Cu Zn Ga Ge As Se Br Kr
 Rb  Sr  Y  Zr  Nb  Mo  Tc  Ru  Rh  Pd  Ag  Cd  In  Sn  Sb  Te  I  Xe
 Cs  Ba  La  Hf  Ta  W  Re  Os  Ir  Pt  Au  Hg  Tl  Pb  Bi  Po  At  Rn
 Fr Ra  Ac  Rf  Db  Sg  Bh  Hs  Mt  Uuu Uub      Uuq    Uuh    Uuo
     Ce  Pr  Nd  Pm  Sm  Eu  Gd Tb  Dy Ho Er Tm  Yb  Lu    
     Th  Pa  U  Np  Pu  Am  Cm  Bk  Cf  Es  Fm  Md  No  Lr    


noble gases 
Alkali Metals
 Alkaline Earth Metals    


  • These elements are located on the border between metals and non-metals.
  • These elements have properties of metal and non-metals.
  • Some of these elements are semi-conductors (they have a ability to carry an electrical charge under certain conditions).
  • They can be shiny or dull.
  • Their shape is easily changed.
  • They typically conduct heat better and electricity better than nonmetals, but not as well as metals.


1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18
H                                 He
Li Be                        B C N O F Ne
Na Mg                        Al Si     P S Cl Ar
K Ca    Sc Ti V Cr Mn Fe Co Ni Cu Zn Ga Ge    As    Se Br Kr
 Rb  Sr    Y  Zr  Nb  Mo  Tc  Ru  Rh  Pd  Ag  Cd  In  Sn  Sb    Te    I  Xe
 Cs  Ba     La  Hf  Ta  W  Re  Os  Ir  Pt  Au  Hg  Tl  Pb  Bi  Po  At     Rn
 Fr Ra     Ac  Rf  Db  Sg  Bh  Hs  Mt  Uuu Uub      Uuq    Uuh    Uuo
     Ce  Pr  Nd  Pm  Sm  Eu  Gd Tb  Dy Ho Er Tm  Yb  Lu    
     Th  Pa  U  Np  Pu  Am  Cm  Bk  Cf  Es  Fm  Md  No  Lr    


noble gases
Alkali Metals
 Alkaline Earth Metals    


  • These elements are located in group 17 of the periodic table.
  • There are only 4 Halogens (Astantine, At, is a radioactive element and there is dispute as to whether or not it is a halogen or a metalloid).
  • They are non-metallic elements.
  • "Halogen" means "salt-former" because they readily react with metals to form ionic compounds called salts (you may know one, NaCl, commonly called table salt). 
  • They have 7 electrons in their outer shell.
  • They have an oxidation number of -1.
  • At room temperature, Halogens exist in all three states of matter.


1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18
H                                 He
Li Be                        B C N O F Ne
Na Mg                        Al Si     P S Cl Ar
K Ca    Sc Ti V Cr Mn Fe Co Ni Cu Zn Ga Ge    As    Se Br Kr
 Rb  Sr    Y  Zr  Nb  Mo  Tc  Ru  Rh  Pd  Ag  Cd  In  Sn  Sb    Te    I  Xe
 Cs  Ba     La  Hf  Ta  W  Re  Os  Ir  Pt  Au  Hg  Tl  Pb  Bi  Po  At     Rn
 Fr Ra     Ac  Rf  Db  Sg  Bh  Hs  Mt  Uuu Uub      Uuq    Uuh    Uuo
     Ce  Pr  Nd  Pm  Sm  Eu  Gd Tb  Dy Ho Er Tm  Yb  Lu    
     Th  Pa  U  Np  Pu  Am  Cm  Bk  Cf  Es  Fm  Md  No  Lr    


noble gases
  Alkali Metals    
 Alkaline Earth Metals    

Example Halogen:F.jpg


Transition Metals:

  • These elements are found in group 3 through 12 of the periodic table.
  • There are 38 elements in this group.
  • Like all metals they are ductile, malleable, and conduct electricity, and heat.
  • Their oxidation states are variable.
  • This group contains iron, cobalt, and nickel, the only elements known to produce an electric field.
  • They have low ionization energies.
  • They have positive oxidation states.
  • They have high boiling and melting points.


1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18
H                                 He
Li Be                        B C N O  F  Ne
Na Mg                        Al     Si     P S  Cl  Ar
K Ca    Sc  Ti  Cr Mn Fe Co Ni Cu Zn Ga    Ge    As    Se  Br  Kr
 Rb  Sr    Y  Zr  Nb  Mo  Tc  Ru  Rh  Pd  Ag  Cd    In  Sn  Sb    Te    I   Xe
 Cs  Ba     La  Hf  Ta  W  Re  Os  Ir  Pt  Au  Hg  Tl  Pb  Bi  Po  At     Rn
 Fr Ra     Ac  Rf  Db  Sg  Bh  Hs  Mt  Uun Uuu  Uub     Uuq    Uuh    Uuo
     Ce  Pr  Nd  Pm  Sm  Eu  Gd Tb  Dy Ho Er Tm  Yb  Lu    
     Th  Pa  U  Np  Pu  Am  Cm  Bk  Cf  Es  Fm  Md  No  Lr    


noble gases
  Alkali Metals    
  Alkaline Earth Metals   
  Transition Metals   



Other Metals:

  • These elements are located in groups 13 through 18.
  • They are ductile, malleable and lustrous.
  • All elements are solid.
  • They have rather high densities.
  • They have oxidation numbers of +4, -4, +3, -3.


1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18
H                                 He
Li Be                        B C N O  F   Ne
Na Mg                        Al     Si     P S Cl Ar
K Ca    Sc Ti V Cr Mn Fe Co Ni Cu Zn Ga     Ge    As    Se Br Kr
 Rb  Sr    Y  Zr  Nb  Mo  Tc  Ru  Rh  Pd  Ag  Cd    In     Sn    Sb    Te     I   Xe
 Cs  Ba     La  Hf  Ta  W  Re  Os  Ir  Pt  Au  Hg  Tl      Pb  Bi  Po  At     Rn
 Fr Ra     Ac  Rf  Db  Sg  Bh  Hs  Mt Uun Uuu Uub    Uuq   Uuh   Uuo
     Ce  Pr  Nd  Pm  Sm  Eu  Gd Tb  Dy Ho Er Tm  Yb  Lu    
     Th  Pa  U  Np  Pu  Am  Cm  Bk  Cf  Es  Fm  Md  No  Lr    


noble gases
 Alkali Metals     
 Alkaline Earth Metals    
 Transition Metals    
 Other Metals    



Rare Earth Elements:

  • They are found in group 3 of the periodic table and the 6th and 7th periods.
  • There are 30 rare earth elements.
  • They compose the lanthanide and actinide series.
  • One element in the lanthanide and most elements in the actinide series are synthetic (man-made).
  • They tend to be soft and golden in color.
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18
H                                 He
Li Be                        B C N O F Ne
Na Mg                        Al     Si     P S Cl Ar
K Ca    Sc Ti V Cr Mn Fe Co Ni Cu Zn Ga     Ge    As    Se Br Kr
 Rb  Sr    Y  Zr  Nb  Mo  Tc  Ru  Rh  Pd  Ag  Cd    In     Sn    Sb    Te    I   Xe
 Cs  Ba     La  Hf  Ta  W  Re  Os  Ir  Pt  Au  Hg  Tl      Pb  Bi     Po  At     Rn
 Fr Ra     Ac  Rf  Db  Sg  Bh  Hs  Mt Uun Uuu Uub    Uuq   Uuh   Uuo
     Ce  Pr  Nd  Pm  Sm  Eu  Gd Tb  Dy Ho Er Tm  Yb Lu    
     Th  Pa  U  Np  Pu  Am  Cm  Bk  Cf  Es  Fm  Md  No  Lr    



noble gases
  Alkali Metals    
 Alkaline Earth Metals    
 Transition Metals    
 Other Metals    


Atomic Mass

The atomic mass of an element, that which appears on the periodic table, is the average of the isotopic masses. Now, you might be wondering what an isotope is. Isotopes are atoms of the same element with different numbers of neutrons. Because there are different numbers of neutron in isotopes then the mass of the isotope is larger then that of the actual atom. The mass we see on the periodic table is the sum of all the isotopic masses times their percent natural abundance (the relative abundance of an isotope found in nature). Lets look at an example.

The atomic mass of Carbon on the periodic table reads 12.011u. We know, however, that carbon-12 has a mass of 12u- so why is the mass on the periodic table slightly larger? Carbon occurs in two forms, Carbon-12 and Carbon-13. These atoms have 6 and 7 neutrons, and masses of 12u and 13.00335u respectively. The percent natural abundance of these elements are Carbon-12, 98.892% and Carbon-13, 1.108%. When we multiply the percent natural abundances by the masses we get the following:

12.00u (0.98892) + 13.0335u (0.01108) = 12.011u

This value of 12.011u is what we see on the periodic table. The mass is driven up from 12u because of the mass of Carbon-13, even if its percent natural abundance is small. Therefore, it should be noted that the masses we see on the periodic table, for atoms with isotopes, is always slightly larger then the mass of the actual atom.

The letter "u" stands for Atomic Mass Unit, also known as a dalton (Da). It is the standard unit of mass for atoms and molecules and is approximately 1/12 the mass of a carbon-12 atom.

c6 (1).jpg


To represent any atom, there needs to be the chemical symbol, the number of protons, neutrons, and electrons.  This could be shown like this:


Since isotopes have different masses,they are written differently.  For example,there is Carbon-12 and Carbon 13 are represented as:

                                                carbon isotopes.jpg   

Carbon-12 and Carbon-13 have the same number of protons (6), but have different number of neutrons; Carbon-12 has 6 neutrons but Carbon-13 has 7. 


Ions are atoms that carry net charges because it lost or gained an electron.  Gaining an electron(s) to an electrically neutral atom would produce a negatively charged ion.  Losing an electron(s) would result in a positively charged ion.  Note that the number of protons does not change within the process.  The charge on an ion is equal to the number of electrons subtracted from the number of protons. This is shown as:

Another example is 16O2- ion.  There are 8 protons, 8 neutrons, and 10 electrons (8 protons - 10 electrons = -2).

Elements: Fun Facts

Elements Discoverer Year Discovered Color Uses
Hydrogen Henry Cavendish 1766 colorless

oil refining processes, metal refining, chemical/scientific applications, formerly balloons

Helium Jules Janssen, Norman Lockyer 1868 colorless deep sea diving, balloons, lasers, supercold refrigerant
Lithium Johan A. Arfwedson 1817 silver- white cooling systems, ceramics, lubricants, batteries,  impact resistant ceramic cookware
Beryllium Louis Vauquelin 1798 silver- gray spacecraft, missiles, aircrafts
Boron Sir Humphry Davy, J.L Gay-Lussac 1808 black heat resistant alloys, stiff fibers, semiconductor
Carbon Unknown ancient in lineage graphite is black, diamond is colorless steel, filters, wood, paper, cloth, plastic, electrodes, fibers
Nitrogen Daniel Rutherford 1772 colorless forms most of the atmosphere, breathing, fire, minerals, oxides
Oxygen Carl Wilhelm Scheele 1772 colorless as a gas, liquid is pale blue. Ozone is blue. found in air, breathing aid, rocket fuel, steel manufacturing, oxidizer for welding etc.
Fluorine Joseph Henri Moissan 1886 greenish refrigerants, lasers, supercold refrigerants, fluoro-polymers, toothpaste
Neon Daniel Rutherford 1772 colorless neon tubes in advertising signs
Sodium Sir Humphrey Davy 1807 silvery medicine, agriculure, salt, baking soda, antacids, lye, soap, street lamps
Magnesium Sir Humphrey Davy 1808 grayish airplanes, missles, cars, flares, antacids
Aluminum Hans Christian Oersted 1825 silver airplanes, soda cans, kitchenware, clay, ceramics
Silicon Jons Berzelius 1823 grey glass, semiconductor, computer chips, siloxane rubber
Phosphorus Henning Brand 1669 white matches and other incediary applications, phosphate for fertilizers, detergents, additives
Sulfur Unknown very old in lineage yellow

sulfuric acid, gunpowder, medicines, rubber treatment

Chlorine Carl Wilhelm Scheele 1774 green water treatment, bleaches, drinking waters, plastic and solvents production
Argon Sir William Ramsay 1894 colorless lighting (light bulbs), "neon" tubes, lasers, welding gas, inter-pane window gas
Potassium Sir Humphrey Davy 1807 silvery salts, nerves, nutrient in fruits and vegetables, soap, fertilizer, potash, matches, gunpowder
Calcium Sir Humphrey Davy 1808 silvery life sustaining agent for bones and shells
Scandium Lars Nilson 1879 silvery aluminum alloys, racing bikes, stadium lamps, furnace bricks, aquamarines
Titanium William Gregor 1791 silvery prostheses and implants, white pigment, structural metal, racing bikes, paper, catalyst
Vanadium Nils Sefstrom 1830 silvery catalyst, dye, color-renewer, alloying agent
Chromium Louis Vauquelin 1797 grey stainless steel, corrosion-resistant plating
Manganese Johann Gahn 1774 silver/greyish steel, batteries, ceramics
Iron Unknown ancient in lineage silvery steel and other alloys, wrought iron
Cobalt George Brandt 1737 silver magnets, ceramics, special glasses, alloying agent
Nickel Alex Cronstedt 1751 white various metal alloys incuding for electroplating, nickel-cadmium batteries
Copper Unknown ancient in lineage red/ orange electrical conductor, jewelry, coins, plumbing, brass, bronze, and other alloys
Zinc Andreas Marggraf 1746 bluish metal coating, rust protection
Gallium Paul Emile Lecoq de Boisbaudran 1875 white/ silver semiconductor protection
Germanium Clemens Winkler 1886 grayish semiconductor, transistors, rectifiers, diodes, photocells, lenses, infrared windows
Arsenic Unknown ancient in lineage grey Poison, semiconductor dopant
Selenium Jons Berzelius 1871 grey photoelectric cells, TVs, cameras
Bromine Antoine J. Balard 1826 red disinfectant, pools and spas, photo film, flame retardant, leaded gas, sedatives
Krypton Sir William Ramsay 1898 colorless lighting
Rubidium R. Bunsen 1861 silver catalyst, photocells, atomic clocks, global navigation (GPS), vacuum tube scavenger
Strontium A. Crawford 1790 yellowish flares, fireworks, crimson color
Yttrium Johann Gadolin 1794 silvery color TVs, radars
Zirconium Martin Klaproth 1789 greyish nuclear applications
Niobium Charles Hatchet 1801 white chemical pipelines, superconductors, magnetic levitation trains, MRI magnets
Molybdenum Carl Wilhelm Scheele 1778 silvery aircraft, missiles, alloying agent
Technetium Carlo Perrier 1937 N/A Tc-99m is used for radioactive tracing in medicine
Ruthenium Karl Klaus 1844 silvery heat resistant alloys
Rhodium William Wollaston 1803 silvery coatings, catalysis
Palladium William Wollaston 1803 white jewelry, medical instruments
Silver Unknown ancient in lineage silver jewelry, photography, electrical conductor, coins
Cadmium Fredrich Stromeyer 1817 silvery poisonous, nickel-cadmium batteries
Indium Ferdinand Reich 1863 silvery coating of high-speed bearings
Tin Unknown ancient in lineage white coating for steel cans, bronze
Antimony Unknown ancient in lineage bluish hardens lead, plastics, chemicals
Tellurium Franz Muller von Reichenstein 1782 silvery coloring of glass and ceramics, thermoelectric devices
Iodine Bernard Courtois 1811 blackish solid; purple vapors disinfectant for wounds and drinking water, added to salt to prevent thyroid disease, photo film
Xenon Sir William Ramsay 1898 colorless powerful lamps, bubble chambers
Cesium Fustov Kirchoff 1860 silver removes air traces in vacuum tubes
Barium Sir Humphrey Davy 1808 silver medical applications, fireworks colorant
Lanthanum Carl Mosander 1839 white expensive camera lenses
Cerium W. von Hisinger 1803 grey heat-resistant alloys
Praseodymium C.F. Aver von Welsbach 1885 N/A coloring glass and ceramics
Neodymium C.F. Aver von Welsbach 1925 silvery coloring glass and ceramics, infrared radiation filtering
Promethium J.A. Marinsky 1945 N/A luminous dials, sheet thickness gauges
Samarium Paul Emile Lecoq de Boisbaudran 1879 silver magnets, in alloys with cobalt, and nuclear reactors
Europium Eugene Demarcay 1901 silver color TVs
Gadolinium Jean de Marignac 1880 silvery magnetic
Terbium Carl Mosander 1843 silvery color TVs
Dysprosium Paul Emile Lecoq de Boisbaudran 1886 N/A nuclear reactors
Holmium J.L. Soret 1878 silver nuclear reactors
Erbium Carl Mosander 1843 greyish ceramics
Thulium Per Theodor Cleve 1879 silvery power for portable x-ray machines
Ytterbium Jean de Marignac 1878 silvery metallurgical and chemical experiments
Lutetium Georges Urbain 1907 silvery cancer-fighting photodynamic (light-activated) medicine
Hafnium Dirk Coster 1923 silver nuclear reactors
Tantalum Anders Ekeberg 1802 grey capacitors, camera lenses
Tungsten Fausto and Juan Jose de Elhuyar 1783 silver used widely in electronics industry, hardening alloy, welding electrode
Rhenium Walter Noddack 1925 silvery filaments for mass spectrographs
Osmium Smithson Tenant 1803 silvery tip gold pen points, instrument pivots, electrical light filaments
Iridium S. Tenant 1804 white tip gold pens, crucible and special containers
Platinum Julius Scaliger 1735 silvery jewelry, catalyst, scientific applications
Gold Unknown circa 3000 BC gold electronics, jewelry, coins
Mercury Unknown ancient in lineage silver thermometers, barometers, fluorescent lamps, batteries, amalgams
Thallium Sir William Crookes 1861 bluish rat and ant poisons, detecting infrared radiation
Lead Unknown ancient in lineage bluish batteries, solder, ammunition, shielding against radiation, fishing line weights 
Bismuth Unknown ancient in lineage white pharmaceuticals, fuses, water sprinklers against fire
Polonium Pierre and Marie Curie 1898 N/A first radioactive element found, small traces in nature, anti-static brushes, tobacco
Astatine D.R. Corson 1940 N/A cancer medicine
Radon Fredrich Ernst Dorn 1898 colorless surgical implants for cancer treatment, environmental hazards
Francium Marguerite Derey 1939 N/A studied in laser atom traps
Radium Pierre and Marie Curie 1898 silvery treating cancer, formerly for glowing dials
Actinium Andre Debierne 1899 silvery small traces in nature, cancer medicine, neutron source, radwaste
Thorium Jons Berzelius 1828 silvery strong alloys, ultraviolet photoelectric cells, possible nuclear fuel in future
Protactinium Fredrich Soddy 1917 N/A N/A
Uranium Martin Klaproth 1789 silvery fuel for nuclear reactors, ammunition (illegitimate), shielding
Neptunium E.M. McMillan 1940 N/A N/A
Plutonium G.T. Seaborg 1940 N/A bombs, nuclear reactors
Americium G.T. Seaborg 1945 N/A smoke detectors
Curium G.T. Seaborg 1944 N/A scientific instruments, mineral analyzers
Berkelium  G.T. Seaborg 1949 N/A N/A
Californium G.T. Seaborg 1950 N/A scientific instruments, mineral analyzers
Einsteinium Argonne, Los Alamos, University of California 1952 N/A N/A
Fermium Argonne, Los Alamos, University of California 1953 N/A N/A
Mendelevium G.T. Seaborg 1955 N/A N/A
Nobelium Nobel Institute for Physics 1957 N/A N/A
Lawrencium Albert Ghiorso 1961 N/A N/A
Rutherfordium Albert Ghiorso 1969 N/A N/A
Dubnium Albert Ghiorso 1970 N/A N/A
Seaborgium Albert Ghiorso 1974 N/A N/A
Bohrium Peter Armbruster, Gottfried Munzenber and others 1976 N/A N/A
Hassium Peter Armbruster, Gottfried Munzenber and others 1984 N/A N/A
Meitnerium Heavy Ion Research Laboratory 1982 N/A N/A
Ununnilium Organessian, et al 1987 N/A N/A
Unununium S. Hofmann 1994 N/A N/A
Ununbium S. Hofmann, V. Ninov, F. P. Hessbuger 1996 N/A N/A


  1. Pettrucci, Ralph H. General Chemistry: Principles and Modern Applications. 9th. Upper Saddle River: Pearson Prentice Hall, 2007
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1. Who was the first to suggest the idea of the atom?

A.     Democritus


B.     Aristotle

C.     Gassendi

D.    Newton

2. What were Aristotle’s four qualities of matter?

A.     Fire, Air, Earth, Water

B.     Hot, Dry, Wet Cold

C.     Winter, Spring, Summer, Fall

D.    Solid, Liquid, Gas, Aqueous

3. How did Gassedi first explain how atoms are held together?

A.     Magnetic forces

B.     Supernatural Forces

C.     Very sticky balls

D.     Balls with hooks

4. Who was the first to coin the term “element”?

A.     Aristotle

B.     Gassendi

C.     Newton

D.    Boyle

5. What is Boron’s atomic number:

A.     1

B.     7

C.     20

D.    5

6. What is the elemental symbol of Silicon?

A.     S

B.     Sl

C.     Si

D.    Sc

7. Which of the following is a property of a noble gas:

A.     They are highly reactive

B.     They are located in Period 18

C.     They are stable

D.    They have oxidation number +1

8. What does Halogen mean?

A.     Salt former

B.     Solid former

C.     Maker of carbonates

D.    Maker or sulfates

9. Alkaline Earth metals have what oxidation number:

A.     +1

B.     +2

C.     -1

D.    -2

10.  What group of the periodic table are Rare Earth Metals found in?

A.     3

B.     4

C.     7

D.    8

ANSWERS: 1.A 2.B 3.D 4.D 5.D 6.C 7.C 8.A 9.B 10.A


  • Joelle Fregeau, Ryan Cheung, Mark Tye