Chem 1405 homework chap2
1. An analysis of a 5.0 g sample pyrite ("fool's gold") revealed that it contained 2.3 g of
iron and 2.7 g of sulfur. What is the mass percentage of iron in fool's gold? (Section 2.1)
a. 54% b. 46% c. 2.3%
2. Calculate the atomic mass of strontium, which has four naturally occurring isotopes:
Natural abundance (%) Atomic mass ( amu)
0.56
83.91
9.86
85.91
7.02
86.91
82.56
87.91
a. 54.66 b. 87.62 c. 892.3
3. A potassium atom contains 19 protons, 19 electrons, and 20 neutrons. What is the
charge on a potassium ion that contains 19 protons, 18 electrons, and 20 neutrons?
(Section 2.4)
a. 0 b. -1 c. +1
4. Complete the following table by filling in the blanks.
Protons
Neutrons
Electrons
Mass( amu) Element
19
20
34
79
20
40
11
23
5. Which of the following statements about the isotopes of an element is true? (Section
2.5)
a. Atoms that are isotopes of one another have different atomic masses.
b. Atoms that are isotopes of one another have different numbers of electrons.
c. Atoms that are isotopes of one another have different atomic numbers.
6. Which of the following pairs of elements is likely to undergo similar chemical
reactions? (Section 2.6)
a. Li and Be b. Cl and Br c. K and F
7. How many valence electrons does carbon have? (Section 2.10)
a. 2 b. 4 c. 14
8. Which elements are described by the following electron configurations?
( a) 1s22s22p63s2 ( b) 1s22s22p63s23p4 ( c) 1s22s22p63s23p64s1
a. Mg, S, K b. Al, S, Na c. Mg, O, K
9. Which elements are described by the following electron configurations?
( a) [ He] 2s22p1; ( b) [ He] 2s22p5; ( c) [ Ar] 4s2
a. B, S, K
b. Al, F, Na c. B, F, Ca
10. A negatively charged anion M-2 has an electronic configuration of 1s22s22p6, what is
the element M?
a. F
b. Ca
c. O