Question

Answer each of the following questions:
(a) Of the elements $S,Se$ and $Cl$ which has the largest atomic radius?
(b) Which has the larger radius, $Br$ or $B{r}^{-}$?
(c) Which should have the largest difference between the first and second ionization energy:

$Si,Na,P$ or $Mg?$
(d) Which has the largest ionization energy?
$N,P,As.$
(e) Which of the following has the largest radius?
$O^{2-},N^{3-}$ or $F^{-}$

• A. $\left(a\right)Se\left(b\right)B{r}^{-}\left(c\right)Na\left(d\right)N\left(e\right)N^{3-}$
• B. $\left(a\right)Cl\left(b\right)B{r}^{-}\left(c\right)Na\left(d\right)N\left(e\right)N^{3-}$
• C. $\left(a\right)S\left(b\right)Br\left(c\right)Mg\left(d\right)N\left(e\right)N^{3-}$
• D. None of these

Answer 1

Answer: (A)

$\left(a\right)Se\left(b\right)B{r}^{-}\left(c\right)Na\left(d\right)N\left(e\right)N^{3-}$

(a) Atomic radius decreases from left to right and increases down the group in the periodic table. But the increase in atomic radius is more significant down the group because down the group number of shells increase in a consecutive element.

(b) The radius of an anion is larger than the parental atom. The anion is formed by a gain of electrons. The effective positive charge in the nucleus is less, so the less inward pull is experienced. Hence $B{r}^{-}$ has a large radius.

(c) In $Na$ loss of the second electron takes place from a stable configuration, hence there is a huge difference between first and second ionization energies in sodium.

(d) Ionisation energy is largest for nitrogen because of its half-filled orbital and small in size.

(e) Because of the gain of more electrons, $N^{3-}$ has the largest size since gain of electrons led to decrease in effective nuclear charge.