| 1. | SiO2 | 2. | CaO |
| 3. | Al2O3 | 4. | SO2 |
| 1. | More shielding of paired electrons in 2p orbital of oxygen. |
| 2. | Half-filled stable configuration of nitrogen. |
| 3. | More Z effective of oxygen. |
| 4. | Small atomic size of oxygen. |
| 1. | The p-block has 6 columns because a maximum of 6 electrons can occupy all the orbitals in a p-shell. |
| 2. | The d-block has 8 columns because a maximum of 8 electrons can occupy all the orbitals in a d-subshell. |
| 3. | Each block contains a number of columns equal to the number of electrons that can occupy that subshell. |
| 4. | The block indicates a value of azimuthal quantum number (l) for the last subshell that received electrons in building up the electronic configuration. |
| Assertion (A): | Na+ and Al3+ are isoelectronic but the magnitude of ionic radius of Al3+ is less than that of Na+. |
| Reason (R): | The magnitude of effective nuclear charge of the outer shell electrons in Al3+ is greater than that in Na+. |
| 1. | Both (A) and (R) are True and (R) is the correct explanation of (A). |
| 2. | Both (A) and (R) are True but (R) is not the correct explanation of (A). |
| 3. | (A) is True and (R) is False. |
| 4. | Both (A) and (R) are False. |
| Assertion (A): | The ionic size of Mg2+>Al3+. |
| Reason (R): | In isoelectronic species, the greater the nuclear charge, the smaller the size. |
| 1. | Both (A) and (R) are True and (R) is the correct explanation of (A). |
| 2. | Both (A) and (R) are True but (R) is not the correct explanation of (A). |
| 3. | (A) is True but (R) is False. |
| 4. | (A) is False but (R) is True. |