Choose the correct statements for element ${}_9{}^{19}\mathrm{M}.$

a. Formation of ${\mathrm{M}}^{-}$ is an endothermic process.

b. It's anion is isoelectronic with neon.

c. It has the smallest size in its period.

d. It has the highest electron gain enthalpy in its group.

Identify the following statements is true and false.

${\mathrm{S}}_1$: Among ${\mathrm{Li}}^{-}, {\mathrm{Be}}^{-}, {\mathrm{B}}^{-}$ and ${\mathrm{C}}^{-},$ ${\mathrm{Be}}^{-}$ is the least stable ion.

${\mathrm{S}}_2$: If the same element is forming oxides in different oxidation states, then the oxide in which the element shows the highest oxidation state will be highly acidic in nature.

${\mathrm{S}}_3$: Amphiprotic oxide is one which can accept and release ${\mathrm{H}}^{+}$ ions.

${\mathrm{S}}_4$: In alkaline-earth metals, electronegativity values decrease down the group.

The energy of an electron in a hydrogen-like is given by ${\mathrm{E}}_{\mathrm{n}}=-\left(2.18\times {10}^{-18}\right)\left(\frac{{\mathrm{Z}}^2}{{\mathrm{n}}^2}\right).$

Whereas: $\mathrm{n}$ is the principal quantum number and $\mathrm{Z}$ is the atomic number of the element.

The ionization energy (in $\mathrm{kJ} {\mathrm{mol}}^{-1}$) of the ${\mathrm{Li}}^{2+}$ ion is

Atomic numbers of some elements are given below. The number of elements from the following that will be placed in group $2$ of the modern periodic table is________.

$3, 4, 7, 12, 18, 20, 26, 32, 38$

The number of elements from the following which have valence electron(s) in the $\mathrm{M}$-shell is_______.

$\mathrm{Si}, \mathrm{C}, \mathrm{N}, \mathrm{Be}, \mathrm{Al}, \mathrm{S}, \mathrm{F}, \mathrm{B}, \mathrm{Li}, \mathrm{Mg}, \mathrm{O}, \mathrm{Ar}$

How many of the following elements are more electronegative than Boron.

(i) $\mathrm{H}$ (ii) $\mathrm{Li}$ (iii) $\mathrm{Be}$ (iv) $\mathrm{C}$ (v) $\mathrm{N}$ (vi) $\mathrm{O}$ (vii) $\mathrm{F}$