Classification of Elements and Periodicity in Properties
Test 10

For isoelectronic species (10 electrons), radius decreases with increasing nuclear charge: \(\ce{Mg^2+}\) (Z=12) < \(\ce{Na+}\) (Z=11) < \(\ce{F^-}\) (Z=9).

In period 4 d-block (Sc to Zn), boiling point peaks with strong metallic bonding. Cr (group 6) has the highest boiling point due to its \(3d^5 4s^1\) configuration and maximum unpaired electrons enhancing bonding.

Second ionization enthalpy peaks when removing an electron from a stable \(\ce{X+}\) ion. Rb (after losing one electron, becomes \(\ce{Rb+}\) with \(1s^2 2s^2 2p^6 3s^2 3p^6 3d^{10} 4s^2 4p^6\)) has the highest value in period 5.

Oxides of non-metals (right side of periodic table) are acidic. \(\ce{SO3}\) (group 16) is acidic, while \(\ce{Na2O}\) (group 1), \(\ce{MgO}\) (group 2), and \(\ce{Al2O3}\) (group 13, amphoteric) are not purely acidic.

Basic oxides are formed by metals, especially on the left side of the periodic table. K (group 1) forms \(\ce{K2O}\), a basic oxide, while C, S, and P form acidic or amphoteric oxides.

Thermal stability of group 1 carbonates increases down the group due to larger cation size stabilizing the lattice. \(\ce{Cs2CO3}\) is the most stable among Li, Na, K, and Cs carbonates.

Third ionization enthalpy peaks when removing an electron from a noble gas-like \(\ce{X^2+}\) ion. Mg (after losing two electrons, becomes \(\ce{Mg^2+}\) with \(1s^2 2s^2 2p^6\)) has the highest value.

Atomic radius increases down a group. Among He, Ne, Ar, and Rn (group 18), Rn (period 6) has the largest radius.

The sixth period (\(n=6\)) includes \(6s\), \(4f\), \(5d\), and \(6p\) orbitals, accommodating 32 electrons, hence 32 elements (Cs to Rn).

Second ionization enthalpy is highest when removing an electron from a stable configuration. Na (after losing one electron, becomes \(\ce{Na+}\) with noble gas configuration) has the highest value compared to Mg, Al, or Si.