Answer
The Group A or representative elements have their last electrons filling the outer ns and np orbitals, whereas most Group B elements have their last electrons filling the (n-1)d orbitals. Look to the tables to compare their properties. For example, Group 3A elements are representative elements and have the ns$^2 np^1$ outer electron configuration, with 3 valance electrons. Boron is a metalloid and crystallizes as a covalent solid (oxidation states ranging from +3 to –3), while the rest are metals forming ions with +1 or +3 oxidation states. Aluminum ions only have a +3 oxidation state. Group 3B elements are transition metals, with the ns2(n-1)d1 outer electron configuration and tend to have a +3 oxidation state.
Work Step by Step
The Group A or representative elements have their last electrons filling the outer ns and np orbitals, whereas most Group B elements have their last electrons filling the (n-1)d orbitals. Look to the tables to compare their properties. For example, Group 3A elements are representative elements and have the ns$^2 np^1$ outer electron configuration, with 3 valance electrons. Boron is a metalloid and crystallizes as a covalent solid (oxidation states ranging from +3 to –3), while the rest are metals forming ions with +1 or +3 oxidation states. Aluminum ions only have a +3 oxidation state. Group 3B elements are transition metals, with the ns2(n-1)d1 outer electron configuration and tend to have a +3 oxidation state.
