Chapter 2 Atoms, Molecules and Ions

1. Chapter 2Atoms, Molecules and Ions Chemistry: The Central Science, 10th edition Theodore L. Brown, H. Eugene LeMay, Jr., and Bruce E. Bursten

2. a. • the law of conservation of matter • the law of multiple proportions • the law of constant composition • the law of conservation of grams

3. a. • the law of conservation of matter • the law of multiple proportions • the law of constant composition • the law of conservation of grams

4. b. • The second compound must have twice as many oxygen atoms per carbon atom as the first compound. • The second compound must have half as many oxygen atoms per carbon atom as the first compound. • The second compound contains half as many carbon atoms as the first compound. • The first compound contains half as many carbon atoms as the second compound.

5. b. • The second compound must have twice as many oxygen atoms per carbon atom as the first compound. • The second compound must have half as many oxygen atoms per carbon atom as the first compound. • The second compound contains half as many carbon atoms as the first compound. • The first compound contains half as many carbon atoms as the second compound.

6.  particles are scattered equally across a range of deflection angles due to the high density of the foil nuclei. • Most  particles pass through the foil without being deflected because most of the volume of the atoms that comprise the foil is empty space. • Most  particles are scattered at acute angles as they pass close to the foil nuclei. • Most  particles are deflected in a backwards direction from the foil due to the high density of the foil atom nuclei.

7.  particles are scattered equally across a range of deflection angles due to the high density of the foil nuclei. • Most  particles pass through the foil without being deflected because most of the volume of the atoms that comprise the foil is empty space. • Most  particles are scattered at acute angles as they pass close to the foil nuclei. • Most  particles are deflected in a backwards direction from the foil due to the high density of the foil atom nuclei.

8. a. • Cannot determine number of electrons without additional information. • The atom has 30 electrons. • The atoms has 15 electrons. • The atom has no electrons unless it is charged.

9. a. • Cannot determine number of electrons without additional information. • The atom has 30 electrons. • The atoms has 15 electrons. • The atom has no electrons unless it is charged.

10. b. • The protons reside in the nucleus of the atom. • The protons are evenly distributed throughout the atom. • The protons are dispersed with the electrons around the nucleus. • The protons reside in a shell just outside the nucleus.

11. b. • The protons reside in the nucleus of the atom. • The protons are evenly distributed throughout the atom. • The protons are dispersed with the electrons around the nucleus. • The protons reside in a shell just outside the nucleus.

12. The 52.94 amu value and the 51.99 amu value represent two different isotopes of chromium. • The atomic weight of chromium is less than the mass of the specific chromium atom since atomic weights are used to describe neutral atoms. • The atomic weight of 51.99 amu is for a different isotope than the 52.94 amu mass. • The atomic weight of chromium (51.99 amu) is an average atomic mass of all the naturally occurring isotopes of chromium.

13. The 52.94 amu value and the 51.99 amu value represent two different isotopes of chromium. • The atomic weight of chromium is less than the mass of the specific chromium atom since atomic weights are used to describe neutral atoms. • The atomic weight of 51.99 amu is for a different isotope than the 52.94 amu mass. • The atomic weight of chromium (51.99 amu) is an average atomic mass of all the naturally occurring isotopes of chromium.

14. a. • C • Cr • Cl • Co

15. a. • C • Cr • Cl • Co

16. b. • 3rd and Group VIIA • 2nd and Group VIA • 2nd and Group VA • 3rd and Group VIIIA

17. b. • 3rd and Group VIIA • 2nd and Group VIA • 2nd and Group VA • 3rd and Group VIIIA

18. c. • 13 • 19 • 17 • 27

19. c. • 13 • 19 • 17 • 27

20. d. • metal • nonmetal

21. d. • metal • nonmetal

22. a. • CH • CH3 • CH6 • C2H6

23. a. • CH • CH3 • CH6 • C2H6

24. b. • CH • CH3 • C2H2 • CH6

25. b. • CH • CH3 • C2H2 • CH6

26. c. • perspective model • visual depth model • ball and stick model • space-filling model

27. c. • perspective model • visual depth model • ball and stick model • space-filling model

28. The formula for calcium oxide is actually Ca2O. • The number of Ca2+ ions paired with O2– ions in a compound can vary. • Two Ca2+ ions can never be found in nature with an O2– ion. • We write empirical formulas for ionic compounds.

29. The formula for calcium oxide is actually Ca2O. • The number of Ca2+ ions paired with O2– ions in a compound can vary. • Two Ca2+ ions can never be found in nature with an O2– ion. • We write empirical formulas for ionic compounds.

30. Calcium only appears as a 2+ ion in ionic compounds and hence needs no Roman numeral. • Roman numerals are always optional after the metal in ionic compounds. • Calcium oxide should also be named with a Roman numeral (II) after calcium. • Transition metals always require Roman numerals when in ionic compound names.

31. Calcium only appears as a 2+ ion in ionic compounds and hence needs no Roman numeral. • Roman numerals are always optional after the metal in ionic compounds. • Calcium oxide should also be named with a Roman numeral (II) after calcium. • Transition metals always require Roman numerals when in ionic compound names.

32. All three suffixes relate to the number of oxygens in an anion. • -ide is typically used for 1-anions, while -ate and -ite are for 2- and 3-anions respectively. • -ide usually means monoatomic anion and -ate and -ite signify differing numbers of oxygens in oxyanions. (-ite anions have one less O atom than -ate anions) • -ide, -ate, and -ite convey information about the acid/base characteristics of anions.

33. All three suffixes relate to the number of oxygens in an anion. • -ide is typically used for 1-anions, while -ate and -ite are for 2- and 3-anions respectively. • -ide usually means monoatomic anion and -ate and -ite signify differing numbers of oxygens in oxyanions. (-ite anions have one less O atom than -ate anions) • -ide, -ate, and -ite convey information about the acid/base characteristics of anions.

34. BO44– and SiO33– • BO33– and SiO44– • BO43– and SiO34– • BO34– and SiO43–

35. BO44– and SiO33– • BO33– and SiO44– • BO43– and SiO34– • BO34– and SiO43–