Q14.9 P - Chemistry: Molecular Nature Of Matter And Change

Question

Explain the horizontal irregularity in the size of the most common ions of Period 3 elements.

Step-by-Step Solution

Answer

The elements on the left side in period 3 have low IE. Hence, they form cations by losing electrons. The loss of electrons leads to an ion smaller than an atom, whereas the element on the right side in period 3 has high IE. Hence, they form anions by the gain of electrons. The gain of electrons leads to an ion larger than an atom. As we move from left to right, the size of the isoelectronic goes on increasing.

Step 1: Periodic table

The periodic table comprises s-block, p-block, d-block, and f-block elements. The s-block contains 1A and 2A group elements. The p-block contains 13, 14, 15, 16, 17, and 18 group elements.

Step 2: Explanation

The elements on the left side in period 3 have low IE. Hence, they form cations by losing electrons. The loss of electrons leads to an ion smaller than an atom, whereas the element on the right side in period 3 has high IE. Hence, they form anions through the gain of electrons. The gain of electrons leads to an ion larger than an atom. This irregularity in the size of ions moving from left to right is due to the presence of d-orbitals and the weaker screening effect of d-orbitals.