## Chemistry: Principles and Practice (3rd Edition)

Published by Cengage Learning

# Chapter 2 - Atoms, Molecules, and Ions - Questions and Exercises - Exercises - Page 89: 2.132

#### Answer

(a) Na$_{2}$Se (b) NiBr$_{2}$ (c) N$_{2}$O$_{5}$ (d) CuSO$_{4}$ (e) (NH$_{4}$)$_{2}$SO$_{3}$

#### Work Step by Step

(a) Na$_{2}$Se Sodium (Na) is an alkali metal (group 1A) and has a valence of 1+. Selenium (Se) is in group 6A and has a valence of 2-. We see that sodium and selenium are present in this compound in a 2:1 ratio. (b) NiBr$_{2}$ Nickel (Ni) is a transition metal and has more than one valence. We want the nickel atom that has a valence of 2+ as specified by the Roman numeral II following its name. Bromine (Br) is a halogen (group 7A) and has a valence of 1-. We see that nickel and bromine are present in this compound in a 1:2 ratio. (c) N$_{2}$O$_{5}$ According to the name of this molecular compound, there are two atoms of nitrogen (N) for every five atoms of oxygen (O). (d) CuSO$_{4}$ Copper (Cu) is a transition metal and has more than one valence. We want the copper atom that has a valence of 2+ as specified by the Roman numeral II following its name. Sulfate is an oxoanion with a valence of 2-. We see that copper and sulfate ions are present in this compound in a 1:1 ratio. (e) (NH$_{4}$)$_{2}$SO$_{3}$ Ammonium (NH$_{4}$) is a polyatomic cation with a valence of 1+. Sulfite (SO$_{3}$) is an oxoanion with a valence of 2-. We see that ammonium and sulfite are present in this compound in a 2:1 ratio.

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