Q. No.The explanation for the fact that the first ionization enthalpy of sodium is lower than that of magnesium but its second ionization enthalpy is higher than that of magnesium would be :
1.
Pressure and volume
2.
Lustre and brightness
3.
Atomic size and effective nuclear charge
4.
Availability in nature
The ionization enthalpy of the main group elements tends to decrease down a group due to,
1) Increase in the atomic size of elements and increase in the shielding effect
2) Decrease in the atomic size of elements and increase in the shielding effect
3) Increase in the atomic size of elements and decrease in the shielding effect
4) Decrease in the atomic size of elements and decrease in the shielding effect
The first ionization enthalpy values (in kJ mol–1) of group 13 elements are :
| B | Al | Ga | In | Tl |
| 801 | 577 | 579 | 558 | 589 |
The explanation for the deviation from the general trend can be -
1. Ga has lower ionization enthalpy than Al.
2. Ga has higher ionization enthalpy than Al.
3. Al has higher ionization enthalpy than Ga.
4. Ga has a lesser valence electron than Al.
An element with higher negative electron gain enthalpy in the given pair is:
(i) O or F (ii) F or Cl
1. O, Cl
2. F, F
3. O, F
4. F, Cl
The relationship between 1st and 2 nd electron gain enthalpy of oxygen atom (O) would be :
| 1. | Both values of electron gain enthalpy are negative. |
| 2. | The 1st electron gain enthalpy of (O) is negative while 2 nd is positive. |
| 3. | Both values of electron gain enthalpies are positive. |
| 4. | The 1st electron gain enthalpy of (O) is positive while 2 nd is negative. |
The basic difference between the electron gain enthalpy (Ea) and electronegativity (EN) is:
| 1. | Ea is the tendency to lose electrons, while EN is the tendency to repel the shared pairs of electrons. |
| 2. | Ea is the tendency to gain neutrons, while EN is the tendency to attract the shared pairs of electrons. |
| 3. | Ea is the tendency to donate electrons, while EN is the tendency to attract the shared pairs of molecules. |
| 4. | Ea is the tendency to gain electrons, while EN is the tendency to attract the shared pairs of electrons. |
The statement that "the electronegativity of N on the Pauling scale is 3.0 in all the nitrogen compounds" is incorrect because:
| 1. | Electronegativity of an element is a variable property. |
| 2. | Pauling scale is not used to measure electronegativity. |
| 3. | The electronegativity of N on the Pauling scale is 12.0 |
| 4. | None of the above. |
The correct statement about the radius of a species is :
| 1. | Radius increases during cation and anion formation. |
| 2. | Radius increases during anion formation and decreases during cation formation. |
| 3. | Radius decreases in cation as well as anion. |
| 4. | Radius decreases during anion formation and increases during cation formation. |
The values of the first ionization enthalpies for two isotopes would be:
| 1. | Same. |
| 2. | Different. |
| 3. | Same values but positive for the first and negative for the second. |
| 4. | Same values but negative for the first and positive for the second. |
The reactivity of alkali metals increases, whereas halogen decreases down the group, because:
| 1. | On moving down, ionization enthalpy decreases in group 1 while the electron gain enthalpy becomes less negative in group 17. |
| 2. | On moving down, ionization enthalpy increases in group 1 while the electron gain enthalpy becomes less negative in group 17. |
| 3. | On moving down, ionization enthalpy increases in group 1 while the electron gain enthalpy becomes less positive in group 17. |
| 4. | On moving down, ionization enthalpy decreases in group 17 while the electron gain enthalpy becomes less negative in group 1. |
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