2.9: End of Chapter Problems
Atoms
1. What are the charges and the relative masses of the three subatomic particles?
2. Describe the structure of an atom in terms of its protons, neutrons, and electrons.
Elements
1. What is an element? Why are chemical symbols so useful? What is the source of the letter(s) for a chemical symbol?
2. Write the chemical symbol for the following elements.
bromine
carbon
calcium
gold
manganese
magnesium
neon
nitrogen
silver
3. What element is represented by each chemical symbol?
Na
Hg
P
K
F
I
Pb
Sn
O
Atomic Number, Mass Number, Atomic Symbol, and Isotopes
1. What is the number of protons in the nucleus of each element?
aluminum
iron
carbon
sodium
oxygen
chlorine
2. How many electrons are present in the atoms of each element?
sulfur
iron
argon
magnesium
potassium
iodine
3. How many protons, electrons, and neutrons are in each atom?
4. Why is the atomic number so important to the identity of an atom?
5. What is the relationship between the number of protons and the number of electrons in an atom?
6. How do isotopes of an element differ from each other?
7. What is the mass number of an element?
8. Which are isotopes? Explain .
9. Complete the following table.
| Number of Protons | Number of Neutrons | Element Name | Isotope Symbol |
|---|---|---|---|
|
95 |
153 |
||
|
21 |
potassium |
Atomic Weight
1. In nature the element oxygen exists as three different isotopes, O-16, O-17, and O-18. Which isotope predominates? Explain.
2. Copper exists as a mixture of 2 isotopes. 63 Cu and 65 Cu. Which isotope predominates?
3. Define atomic mass. Why is it considered a weighted average?
4. a. What is an atomic mass unit?
b. What is the atomic weight of zinc in atomic mass units?
c. What is the atomic weight of barium in atomic mass units?
Periodic Table
5. How are the elements organized into the periodic table?
6. Looking at the periodic table, where do the following elements appear?
the metals
the nonmetals
the halogens
the transition metals
the noble gases
7. Describe the trends in atomic radii as related to an element’s position on the periodic table.
8. Using the periodic table, which atom is larger? Explain.
N or Bi
Mg or Cl
Li or F
Na or K
9. a. A potassium atom has ____ core electrons and ____ valence electrons.
b. A silicon atom has ____ core electrons and ____ valence electrons.
c. How many total and valence electrons are in a neutral phosphorus atom?
d. How many total, valence, and core electrons are there in a neutral xenon atom?
Mole-Mass Conversions
1. How many moles are present in 100.0 g of Al?
2. How many moles are present in 25.5 g Na?
3. What is the mass of 8.603 mol of Fe metal?
4. What is the mass of 0.552 mol of Ag metal?
Physical & Chemical Properties
1. Which of the following is a chemical property of iron?
Iron corrodes in moist air
Density = 7.874 g/cm 3
Iron is soft
pure iron melts at 1808 K
2. Which of the following is a physical property of matter?
corrosiveness
pH (acidity)
density
flammability
3. Which of the following is a chemical property?
flammability
melting point
boiling point
density
4. Label each of the following changes as a physical or chemical change.
a. Boiling water
b. A nail rusting
c. A green solution and colorless solution are mixed. The resulting mixture is a solution with a pale green color.
d. Two colorless solutions are mixed. The resulting mixture has a yellow precipitate.
e. A mirror is broken.
f. An iron nail corroded in moist air
g. Copper metal is melted.
h. A catalytic converter changes nitrogen dioxide to nitrogen gas and oxygen gas.