(a) The electronic configuration of an element having 5 electrons in its outermost subshell

should be ns${}^2$ np${}^5$

. This is the electronic configuration of the halogen group. Thus, the

element can be F, Cl, Br, I, or At.

(b) An element having two valence electrons will lose two electrons easily to attain the

stable noble gas configuration. The general electronic configuration of such an element

will be ns2

. This is the electronic configuration of group 2 elements. The elements

present in group 2 are Be, Mg, Ca, Sr, Ba.

(c) An element is likely to gain two electrons if it needs only two electrons to attain the

stable noble gas configuration. Thus, the general electronic configuration of such an

element should be ns${}^2$ np${}^4$

. This is the electronic configuration of the oxygen family.

(d) Group 17 has metal, non–metal, liquid as well as gas at room temperature.