In: Chemistry
Would you expect each of the following atoms to gain or lose electrons when forming ions? Explain details and what is the rule apply to it? 1. P 2. Te
Metals and nonmetals form ions when the compound in which they are found dissolve in water. Metals lose electrons as they ionize and form ions. This gives metals positive charges. Nonmetals gain electrons when they form ions. Keep in mind that there are rarely, if ever, actual ions in compounds. What are often confused for ionic charges are the oxidation numbers which are assigned to elements in compounds. Oxidation numbers are not actual ionic charges.
a. Na == Na^+ (lost 1 e-)
b.Sr == Sr^2+ (lost 2 e-)
c.Ba == Ba^2+ (lost 2 e-)
d.I == I^- (gained 1 e-)
e.Al == Al^3+ (lost 3 e-)
f.S == S^2- (gained 2 e-)
Metals often lose their valence electrons which is why the alkali metals, alkaline earth metals and aluminum have ionic charges of +1, +2 and +3 respectively. If a metal has more than 2 or 3 valence electrons it is unlikely to lose all of the valence electrons. For instance, chromium has six valence electrons, but the most common ionic charge is +3 followed by +2. There are no chromium ions with a charge of +6. (Chromium can exhibit an oxidation number of +6, but remember that oxidation numbers are not actual ionic charges.)
Nonmetals form ions by gaining as many electrons as it takes to have a filled p-sublevel. This is why the halogens form ions with charges of -1, and chalcogens for ions with charges of -2. As tempting as it is to assume that the elements in the nitrogen and carbon families form ions with charges of -3, and -4 respectively, that simply doesn't happen. These would be unstable in water, and those nonmetals would form polyatomic ions instead. This is why there is no P^3- ion in water, but we do observe the PO4^3- ion, in which phosphorous has a +5 oxidation state.