Nitrogen has stable half filled p subshell. So it has the maximum value of first ionization energy.

La, Ce, Pr are the elements belonging to the Lanthanide series.

Both sodium and potassium belongs to the alkali metals and hence they have similar properties.

Sulfur has the highest negative value of electron gain enthalpy.

Cesium is an alkali metal which becomes liquid at 15⁰ C

Sodium, Potassium, and Zinc are all chemical elements that are classified as metals. Calcium is also a metallic element, whereas Sulphur and Iodine are non-metals and water is a compound.

Correct answer is (1). 

Uranium is the heaviest naturally occurring element found in significant quantities on Earth, often cited as the most complex natural element.

Zinc's first ionisation energy is 906 kJ/mol. Zinc has a very high first ionisation enthalpy because an electron has to be removed from 4s orbital of stable configuration (3d¹⁰ 4s²).

Enthalpy of atomisation of manganese is 281 KJ / mol. Enthalpy of atomisation of zinc is 126 KJ / mol.

Sodium (Na) comes from the Latin 'natrium', which does not match its English name. While Tungsten (W) and Potassium (K) also have symbols not matching their English names, Sodium is the lightest among the options provided (Atomic number 11).

The atomic size of elements is Na < Mg < Ca < Cr < Sr. Ionisation potential ∝ 1/(Atomic Size) Na is the smallest atomic size. So, it has highest first ionisation potential.

Hydration energy ∝ 1/(Cation size)

Al⁺³ has maximum hydration energy.

Wrong statement: The second ionisation potential of oxygen is lower than nitrogen.

The second ionisation potential of oxygen is higher than nitrogen.

Wrong statement: Metals possess high electronegativity.

Metals possess low electronegativity.

P. Kernite (Na₂B4O₇.4H₂O) is the mineral of boron. Q. There are two isotopic forms of boron ¹⁰B (19%) and ¹¹B (81%). R. Boron (2427 KJ/mol) has higher second Ionization enthalpy than aluminium (1816 KJ/mol).