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Write the first chemical symbol based on the cation in the compound, including the charge. The name tells us it is gold(I) meaning it carries a 1+ charge. gold(I) = Au+

1.      Use the second member of each group from Group IA to Group 7A to show that the number of valence electrons on an atom of the element is the same as its group number.
(8 points)

Li has 1 valence electron

Cl has 7 valence electrons

(Reference: Chang 9.2)

2.   Explain the following: (3 points)

a.       ionic bond=electrostatic force that holds ions together in an ionic compound.

b.      nonpolar covalent bond=electrons are shared equally between the two atoms.

c.       polar covalent bond= the electrons spend more time in the vicinity of one atom than the other.

3.      Specify which compound in the following pairs of ionic compounds has the higher lattice energy: Explain your choice. (6 points)

a.       KCl or MgO=MgO

b.      LiF or LiBr=LiBr

c.       Mg3N2 or NaCl=NaCl

(Reference: Chang 9.23)

4.      Compare the properties of ionic compounds and covalent compounds. (6 points)

Electronegativity is a property of atoms, not bonds. An ionic bond is formed between elements with very different electronegativities, a covalent bond between atoms with similar electronegativities.

(Reference: Chang 9.32)

5.      Four atoms are arbitrarily labeled D, E, F, and G. Their electronegativities are as follows: D = 3.8, E = 3.3, F = 2.8, and G = 1.3. If the atoms of these elements form the molecules DE, DG, EG, and DF, how would you arrange these molecules in order of increasing covalent bond character?  (4 points)