Correct order of 1st ionisationpotential (IP) among following elements Be, B, C, N, O is

An atom has electronic configuration
$1s^2,2s^2,2p^6,3s^{2}3p^{6}3d^3,4s^2$
It is a member of d- block element because the last electron is filled in d -subshell as $3d^3$ and the following electronic configuration is possible for d-subshell as ${\left(n-d\right)}^{\left(1\text{to}10\right)}$
$\begin{array}{ccccccc}& \text{Group number}& IIIB& IVB& VB& VIB& VIIB\\ & & 3& 4& 5& 6& 7\\ & n{s}^2\left(n-1\right)s^2{p}^6& d^1& d^2& d^3& d^4& d^5\end{array}$
$\begin{array}{cccccc}& VIII& VIII& VIII& IB& IIB\\ & 8& 9& 10& 11& 12\\ & d^6& d^7& d^8& d^9& d^{10}\end{array}$
Hence, it is member of third group