Section 1.12   Page 45
a)  Sulphur and oxygen form two covalent bonds. Both elements are non-metals.  Since each element has six electrons in its outermost shell, to satisfy the octet rule, they must share electrons.

b)  Sodium and iodine form an ionic bond.  Sodium has one electron in its outermost shell and is a metal, whereas iodine has seven electrons in its outermost shell and is a non-metal.  Sodium loses its valence electron to become stable, and iodine gains an electron in its outermost shell.  Each atom follows the octet rule.

c)   Bromine and bromine form covalent bonds because bromine is a non-metal and each atom must share electrons in order to satisfy the octet rule.
H2S is a polar molecule because it has polar covalent bonds and a bent shape, with opposite charges  at opposite ends.  Al the other molecules are non-polar.  Due to their symmetry, any polar bonds are cancelled out, or there are no polar bonds (e.g. H2)
In a covalent bond, two atoms share a pair of electrons.  IOnic bonds form as a result of the transfer of electrons from one atom to another.  As a result, one atom becomes a cation while the other atom becomes an anion.  The electrostatic force of attraction between oppositely charges ions results in the formation of an ionic bond.  In both ionic and covalent bonds, the octet rule is satisfied: all atoms end up with a full outer shell.
a)  Beryllium has a higher electronegativity than strontium because beryllium is in period 2, whereas strontium is in period 5.  Beryllium has a smaller atomic radius than strontium and therefore a stronger pull on its valence electrons than strontium.

b)   Chlorine has a higher electronegativity than sodium because chlorine has a higher atomic number and therefore more protons in its nucleus than sodium.  It therefore has a stronger pull on its valence electrons than sodium,
a)  H - F

b)  C - O

c)  O - H

d)  P - Cl

e)  N - H

f)   P - O

g)  C - N
If the polar bonds are identical and arranged symmetrically around the central atom, their combined pulls cancel each other and the molecule os non-polar.  There are no opposite charges at opposite ends.
a)  An intermolecular bond id a bond between two or more molecules

b)   Dipole-dipole forces form between polar molecules because the slightly positive end of one molecule is attracted to the slightly negative end of a neighbouring molecules,  London dispersion forces form between polar and nonpolar molecules due to temporary imbalances in the positions of electrons in the atoms that make up the molecules.
Intermolecular Forces
Intermolecular force(s)
(LDF, DDF, or both)
hydrogen, H2
carbon tetrachloride, CCl4
hydrogen sulphide, H2S
The boiling point of methane is much lower that the boiling point of hydrogen bromide because methane in a nonpolar molecule whereas hydrogen bromide is polar.  The intermolecular bonds that form between methane molecules (LDF) are fewer and weaker than the intermolecular bonds that form between hydrogen bromide molecules (LDF's and DDF's).  Less energy is required to break the bonds between methane molecules, resulting in a lower boiling point.
a)  Prediction: The molecules that will be affected by the charged object are NCl3 and H2O because these molecules are polar.

b)  Observations:  Samples 1 and 2 could be Br2 and CCl4.  Samples 3 and 4 could be NCl3 and H2O

c)  Analysis: A charged object attracts or repels a thin stream of liquids composed of polar molecules, NCl3 and H2O, but it has no effect on liquids composed of nonpolar molecules, Br2 and CCl4.

d)   Synthesis: The polar molecules, NCl3 and H2O, are slightly positively charged at one end and slightly negatively charged at the other end doe to their shape and the presence of polar covalent bonds.  Thus, the end of the polar molecule that has the opposite charge of the charged object will move toward the charged object.

e)   The liquids were affected by both positive and negative charges because the polar molecules of the liquids are positively charged at one end and negatively charged at the other.  A positively charged object attracts the negatively charged end of the polar molecule, while a negatively charged object attracts the positively charged end of the polar molecule.