Predict the period, of the following elements. $A$ (at. no. $=8$ ), $B$ (at. no. $=11), C$ (at. no. $=28$ ) and D (at. no. $=54)$.

Question

Aicharya · Accepted Answer

Electronic configurations of different elements are
$\mathrm{A} ightarrow 1 s^{2} 2 s^{2} 2 p^{4}$
$\mathrm{~B} ightarrow 1 s^{2} 2 s^{2} 2 p^{6} 3 s^{1}$
$\mathrm{C} ightarrow 1 s^{2} 2 s^{2} 2 p^{6} 3 s^{2} 3 p^{6} 3 d^{8} 4 s^{2}$
$\mathrm{D} ightarrow 1 s^{2} 2 s^{2} 2 p^{6} 3 s^{2} 3 p^{6} 3 d^{10} 4 s^{2} 4 p^{6} 4 d^{10} 5 s^{2} 5 p^{6}$
Element A: $p$-block element
Group number $=10+$ number of electron in the valence shell $=10+6=16$
Period of the element $=$ Principal quantum number of the valence shell $=2$ nd.
Elements B: $s$-block element
Group number = Number of electrons in valence shell $=1$
Period number $=3 \mathrm{rd}$
Element C: $d$-block element
Group number = Number of electrons in penultimate shell and valence shell $=8+2=10$
Period of the $=$ Principal quantum number of the valence shell
$=4 \mathrm{th}$
Element D: $p$-block element
Group number $=10+$ number of electron in the valence shell $=10+8=18$
Period number $=5$ .

Predict the period, of the following elements. $A$ (at. no. $=8$ ), $B$ (at. no. $=11), C$ (at. no. $=28$ )…

Solution