Question

$\begin{array}{cc}Sc-\left[Ar\right]3d^{1}4s^2& Ca-\left[Ar\right]4s^2\\ Mg-\left[Ne\right]3s^2& Co-\left[Ar\right]3d^{7}4s^2\end{array}$
Write down the group and period of each element.

Answer 1

$concept:$

• $\text{group number}\Rightarrow \text{no. of valence electron}$
• $\text{period number}\Rightarrow \text{highest no. of shells}$

Element	Group	Period
$Sc$	$3$	$4$
$Ca$	$2$	$4$
$Mg$	$2$	$3$
$Co$	$9$	$4$