Use the periodic table to answer the following questions.
$(a)$ Identify an element with five electrons in the outer subshell.
$(b)$ Identify an element that would tend to lose two electrons.
$(c)$ Identify an element that would tend to gain two electrons.
$(d)$ Identify the group having metal,non-metal,liquid as well as gas at room temperature.

(N/A) Chromium $(Cr, Z=24)$ has the electronic configuration $[Ar] 3d^5 4s^1$,thus it has five electrons in the outer $3d$ subshell.
$(b)$ Magnesium $(Mg, Z=12)$ has the electronic configuration $[Ne] 3s^2$. It tends to lose two electrons to achieve a stable noble gas configuration.
$(c)$ Oxygen $(O, Z=8)$ has the electronic configuration $[He] 2s^2 2p^4$. It tends to gain two electrons to complete its octet.
$(d)$ Group $17$ (Halogens) contains non-metals $(F, Cl)$,liquid $(Br)$,and metal ($I$ is often considered to have metallic character,though $At$ is also in this group).