Older MCQs might not have the typical A, B, C,
D
choices. They
have choices 1, 2, 3, and a combination of them is the answer. Below is the key that maps such
combinations to the answer.
A
1, 2 and 3 are correct
B
1 and 2 only are correct
C
2 and 3 only are correct
D
1 only is correct
define covalent bonding as electrostatic attraction between the nuclei of two atoms and a shared pair of electrons (a) describe covalent bonding in molecules including: - hydrogen, H\(_2\) - oxygen, O\(_2\) - nitrogen, N\(_2\) - chlorine, Cl\(_2\) - hydrogen chloride, HCl - carbon dioxide, CO\(_2\) - ammonia, NH\(_3\) - methane, CH\(_4\) - ethane, C\(_2\)H\(_6\) - ethene, C\(_2\)H\(_4\) (b) understand that elements in period 3 can expand their octet including in the compounds sulfur dioxide, SO\(_2\), phosphorus pentachloride, PCl\(_5\), and sulfur hexafluoride, SF\(_6\) (c) describe coordinate (dative covalent) bonding, including in the reaction between ammonia and hydrogen chloride gases to form the ammonium ion, NH\(_4^+\), and in the Al\(_2\)Cl\(_6\) molecule
describe, in simple terms, the lattice structure of a crystalline solid which is: (a) giant ionic, including sodium chloride and magnesium oxide (b) simple molecular, including iodine, buckminsterfullerene \( C_{60} \) and ice (c) giant molecular, including silicon(IV) oxide, graphite and diamond (d) giant metallic, including copper
use the differences in Pauling electronegativity values to predict the formation of ionic and covalent bonds (the presence of covalent character in some ionic compounds will not be assessed) (Pauling electronegativity values will be given where necessary)
