Answer Key to Review Problems for Unit 1

Part A:

1) c 2) d 3) d 4) b 5) a 6) e

7) a 8) d 9) b 10) e 11) c

Part B:

1) a) 15 protons, 15 electrons, 17 neutrons

b) 16 protons

2) No, the density is mass/volume or 91.2g/ 8mL = 11.4 g/mL

3) 2

4) a) Be b) chlorine c) Rn d) Fr

5) a) ionic b) molecular c) molecular d) ionic e) ionic

6) a) Fe(NO₃)₃ b) BaS c) Al₂O₃ d) CuCN e) PbCO₃

f) (NH₄)₃PO₄

7) a) Aluminum sulfide

b) Copper (II) phosphate

c) Sodium carbonate

d) Silver Nitrate

e) Cesium dihydrogen phosphate

f) Lithium bicarbonate

8) both have 1s² 2s² 2p⁶ 3s² 3p⁶ electron configuration.

9) Even though both chloride and calcium ion have same electron configuration, the number of protons in the nucleus has not changed in each ion: chlorine has 17 protons and calcium has 20 protons. In chloride ion, the number of electron exceeds the number of protons, thus making it a negatively charged ion. In calcium ion, there is 18 electrons with 20 protons, making the atom positively charged (+2). An anion and a cation will behave differently in a chemical reaction.

10) The valence electrons of an atom are found in the outermost shell of the atom that contains electrons. The core electrons are those in energy levels closer to the nucleus than the outermost energy level. The valence electrons are the electrons gained, lost or shared with other atoms. The arrangement of the elements on the periodic table corresponds to their valence electron configurations. Elements in the same vertical group have similar configuration and similar chemical reactivity.