The scientist who discovered neutron is .

The lower energy state of an atom is called _____. (ground state / excited state)

${}_{17}{}^{35}\mathrm{Cl} \mathrm{and} {}_{17}{}^{37}\mathrm{Cl}$ are _____.

The electronic configuration of an element with atomic number $15$ is _____.

$\mathrm{A} : 2, 8, 5$

$\mathrm{B} : 2, 8, 4$

$\mathrm{C} : 2, 8, 8$

Enter your correct answer as $\mathrm{A}, \mathrm{B} \mathrm{or} \mathrm{C}$.