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1.13.2: Elements, Atoms, and the Periodic Table (Exercises)

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    These are homework exercises to accompany Chapter 2 of the Ball et al. "The Basics of GOB Chemistry" Textmap.

    Exercises

    1. Which of the following substances are elements?

      1. sodium
      2. milk
      3. gold
      4. water
      5. air
      6. liquefied nitrogen

    2. Which of the following substances are elements?

      1. paper
      2. electricity
      3. neon
      4. carbon
      5. wood
      6. concrete

    3. Write the chemical symbol for each element.

      1. silver
      2. sulfur
      3. nitrogen
      4. neon

    4. Write the chemical symbol for each element.

      1. bromine
      2. oxygen
      3. lithium
      4. boron

    5. Explain why it is improper to write CO as the chemical symbol for cobalt.

    6. Explain why it is improper to write NO as the chemical symbol for nobelium.

    7. Complete the following table.

      Element Symbol Element Name
      F  
      Fe  
      I  
      Cr  
      C  
      P  

    8. Complete the following table.

      Element Symbol Element Name
      Mg  
      Mn  
      Ca  
      Cl  
      K  
      Pt  

    Answers

    1.  

      1. element
      2. not an element
      3. element
      4. not an element
      5. not an element
      6. element
    2.
    1. not an element
    2. not an element
    3. element
    4. element
    5. not an element
    6. not an element

    1.  

      1. Ag
      2. S
      3. N
      4. Ne
    4.
    1. Br
    2. O
    3. Li
    4. B

    1. By convention, the second letter in an element’s symbol is always lowercase.

    6. By convention, the second letter in an element’s symbol is always lowercase. Additionally, NO represents a compound.
     
    7.
    Element Symbol Element Name
    F fluorine
    Fe iron
    I iodine
    Cr chromium
    C carbon
    P phosphorus

    8.

    Element Symbol Element Name
    Mg magnesium
    Mn manganese
    Ca calcium
    Cl chlorine
    K potassium
    Pt platinum

    Exercises

    1. Which of the following elements exist as diatomic molecules?

      1. helium
      2. hydrogen
      3. iodine
      4. gold

    2. Which of the following elements exist as diatomic molecules?

      1. chlorine
      2. potassium
      3. silver
      4. oxygen

    3. Why is it proper to represent the elemental form of helium as He but improper to represent the elemental form of hydrogen as H?

    4. Why is it proper to represent the elemental form of chlorine as Cl2 but improper to represent the elemental form of calcium as Ca2?

    Answers

    1.  

      1. no
      2. yes
      3. yes
      4. no
    2.
    1. yes
    2. no
    3. no
    4. yes

    3. Hydrogen exists as a diatomic molecule in its elemental form; helium does not exist as a diatomic molecule.

    4. Chlorine exists as a diatomic molecule in its elemental form; calcium does not exist as a diatomic molecule.

     

    Exercises

    1. Which is smaller—an electron or a helium atom?

    2. Which is larger—a proton or an atom of lead?

    3. Which subatomic particle has a positive charge? Which subatomic particle has a negative charge?

    4. Which subatomic particle is electrically neutral? Does it exist inside or outside the nucleus?

    5. Protons are among the (most, least) massive subatomic particles, and they are found (inside, outside) the nucleus.

    6. Electrons are among the (most, least) massive subatomic particles, and they are found (inside, outside) the nucleus.

    7. Describe why Rutherford used the term planetary model to describe his model of atomic structure.

    8. Why is the planetary model not an appropriate way to describe the structure of an atom?

    9. What happened to most of the alpha particles in Rutherford’s experiment? Explain why that happened.

    10. Electrons account for the (majority, minority) of the (mass, volume) of an atom.

    Answers

    1. An electron is smaller.

    2. An atom of lead is larger.

    1. proton; electron

    4. neutron; inside the nucleus

    1. most; inside

    6. least; outside

    1. Electrons are in orbit about the nucleus.

    8. Electrons do not have specific circular orbits about the nucleus.

    9. Most of the alpha particles went through the metal sheet because atoms are mostly empty space.

    10. minority; mass

     

    Exercises

    1. How many protons are in the nucleus of each element?

      1. radon
      2. tungsten
      3. chromium
      4. beryllium

    2. How many protons are in the nucleus of each element?

      1. sulfur
      2. uranium
      3. calcium
      4. lithium

    3. What are the atomic numbers of the elements in Exercise 1?

    4. What are the atomic numbers of the elements in Exercise 2?

    5. How many electrons are in neutral atoms of the elements in Exercise 1?

    6. How many electrons are in neutral atoms of the elements in Exercise 2?

    7. Complete the following table.

      Number of Protons Number of Neutrons Element Name Isotope Symbol
      80 120    
            \(\mathrm{^{55}_{26}Fe}\)
        2 hydrogen  

    8. Complete the following table.

      Number of Protons Number of Neutrons Element Name Isotope Symbol
            \(\mathrm{^{3}_{2}He}\)
      95 153    
        21 potassium  

    9. State the number of protons, neutrons, and electrons in neutral atoms of each isotope.

      1. 131I
      2. 40K
      3. 201Hg
      4. 19F

    10. State the number of protons, neutrons, and electrons in neutral atoms of each isotope.

      1. 3H
      2. 133Cs
      3. 56Fe
      4. 207Pb

    11. What is the mass number of a gallium atom that has 38 neutrons in it?

    12. What is the mass number of a uranium atom that has 143 neutrons in it?

    13. Complete each sentence.

      1. 48Ti has _____ neutrons.
      2. 40Ar has _____ neutrons.
      3. 3H has _____ neutrons.

    14. Complete each sentence.

      1. 18O has _____ neutrons.
      2. 60Ni has _____ neutrons.
      3. 127I has _____ neutrons.

    Answers

    1.  

      1. 86
      2. 74
      3. 24
      4. 4
    2.
    1. 16
    2. 92
    3. 20
    4. 3

    1. 86, 74, 24, and 4

    4. 16, 92, 20, 3

    1. 86, 74, 24, and 4

    6. 16, 92, 20, 3
    1. Number of Protons Number of Neutrons Element Name Isotope Symbol
      80 120 mercury \(\mathrm{^{200}_{80}Hg}\)
      26 29 iron \(\mathrm{^{55}_{26}Fe}\)
      1 2 hydrogen \(\mathrm{^{3}_{1}H}\)
    8.
    Number of Protons Number of Neutrons Element Name Isotope Symbol
    2 1 helium \(\mathrm{^{3}_{2}He}\)
    95 153 americium \(\mathrm{^{248}_{95}Am}\)
    19 21 potassium \(\mathrm{^{40}_{19}K}\)
     

    1.  

      1. protons: 53; neutrons: 78; electrons: 53
      2. protons: 19; neutrons: 21; electrons: 19
      3. protons: 80; neutrons: 121; electrons: 80
      4. protons: 9; neutrons: 10; electrons: 9
    10.
    1. protons: 1; neutrons: 2; electrons: 1
    2. protons: 55; neutrons: 78; electrons: 55
    3. protons: 26; neutrons: 30; electrons: 26
    4. protons: 82; neutrons: 125; electrons: 82

    11. 69

    12. 235

    13.

    1. 26
    2. 22
    3. 2

    14.

    1. 10
    2. 32
    3. 74

    Exercises

    1. What is the atomic mass of zinc in atomic mass units?

    2. What is the atomic mass of barium in atomic mass units?

    3. What is the average mass of a single magnesium atom in grams?

    4. What is the average mass of a single calcium atom in grams?

    5. What is the mass of 1.000 × 1024 aluminum atoms in grams?

    6. What is the mass of 5.000 × 1023 carbon atoms in grams?

    7. Which has more mass—1 tungsten atom or 11 oxygen atoms?

    8. Which has more mass—1 magnesium atom or 6 helium atoms?

    9. Determine the atomic mass of lithium, given the isotopic composition: 92.4% lithium-7 (mass 7.016 u) and 7.60% lithium-6 (mass 6.015 u).

    10. Determine the atomic mass of neon, given the isotopic composition: 90.48% neon-20 (mass 19.992 u), 0.27% neon-21 (mass 20.994 u), and 9.25% neon-22 (mass 21.991 u).

    11. Determine the atomic mass of magnesium, given the isotopic composition: 78.70% magnesium-24 (mass 23.98 u), 10.13% magnesium-25 (mass 24.99 u) and 11.17% magnesium-26 (mass 25.98).

    12. Determine the atomic mass of bromine, given the isotopic composition: 50.69% bromine-79 (mass 78.9183 u), 49.31% and bromine-81 (mass 80.9163 u). 

    Answers

    1. 65.4 u

    2. 137.33 u

    1. 4.038 × 10−23 g

    4. 6.657 × 10−23 g

    1. 44.81 g

    6. 9.974 g

    7. 1 tungsten atom

    8. 1 magnesium atom

    9. 6.94 u

    10. 20.18 u

    11.  24.30 u

    12.  79.90 u

    Exercises

    1. Which elements have chemical properties similar to those of magnesium?

      1. sodium
      2. fluorine
      3. calcium
      4. barium
      5. selenium

    2. Which elements have chemical properties similar to those of lithium?

      1. sodium
      2. calcium
      3. beryllium
      4. barium
      5. potassium

    3. Which elements have chemical properties similar to those of chlorine?

      1. sodium
      2. fluorine
      3. calcium
      4. iodine
      5. sulfur

    4. Which elements have chemical properties similar to those of carbon?

      1. silicon
      2. oxygen
      3. germanium
      4. barium
      5. argon

    5. Which elements are alkali metals?

      1. sodium
      2. magnesium
      3. aluminum
      4. potassium
      5. calcium

    6. Which elements are alkaline earth metals?

      1. sodium
      2. magnesium
      3. aluminum
      4. potassium
      5. calcium

    7. Which elements are halogens?

      1. oxygen
      2. fluorine
      3. chlorine
      4. sulfur
      5. carbon

    8. Which elements are noble gases?

      1. helium
      2. hydrogen
      3. oxygen
      4. neon
      5. chlorine

    9. Which pairs of elements are located in the same period?

      1. H and Li
      2. H and He
      3. Na and S
      4. Na and Rb

    10. Which pairs of elements are located in the same period?

      1. V and Nb
      2. K and Br
      3. Na and P
      4. Li and Mg

    11. In each pair of atoms, which atom has the greater atomic radius?

      1. H and Li
      2. N and P
      3. Cl and Ar
      4. Al and Cl

    12. In each pair of atoms, which atom has the greater atomic radius?

      1. H and He
      2. N and F
      3. Cl and Br
      4. Al and B

    13. Scandium is a (metal, nonmetal, semimetal) and is a member of the (main group elements, transition metals).

    14. Silicon is a (metal, nonmetal, semimetal) and is a member of the (main group elements, transition metals).

    Answers

    1.  

      1. no
      2. no
      3. yes
      4. yes
      5. no
    2.
    1. yes
    2. no
    3. no
    4. no
    5. yes

    1.  

      1. no
      2. yes
      3. no
      4. yes
      5. no
    4.
    1. yes
    2. no
    3. yes
    4. no
    5. no

    1.  

      1. yes
      2. no
      3. no
      4. yes
      5. no
    6.
    1. no
    2. yes
    3. no
    4. no
    5. yes

    1.  

      1. no
      2. yes
      3. yes
      4. no
      5. no
    8.
    1. yes
    2. no
    3. no
    4. yes
    5. no

    1.  

      1. no
      2. yes
      3. yes
      4. no
    10.
    1. no
    2. yes
    3. yes
    4. no

    11.

    1. Li
    2. P
    3. Cl
    4. Al

    12.

    1. H
    2. N
    3. Br
    4. Al

    13. metal; transition metals

    14. semimetal; main group elements

     

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