Among halogens, the correct order of amount of energy released in electron gain (electron gain enthalpy) is-
1. | F > Cl > Br > I | 2. | F < Cl < Br < I |
3. | F < Cl > Br > I | 4. | F < Cl < Br > I |
The formation of the oxide ion O2- (g), from the oxygen atom requires first an exothermic and then an endothermic step as shown below,
Thus, the process of formation of O2- in the gas phase is unfavorable even though O2- is isoelectronic with neon. It is due to the fact that:
1. | Electron repulsion outweighs the stability gained by achieving noble gas configuration. |
2. | O- ion has a comparatively smaller size than the oxygen atom. |
3. | Oxygen is more electronegative. |
4. | Addition of electrons in oxygen results in a large size of the ion. |
The correct order of increasing electron gain enthalpy with a negative sign for the elements O, S, F, and Cl is :
1. Cl < F < S < O
2. O < S < F < Cl
3. F < S < O < Cl
4. S < O < Cl < F
The correct order of increasing electron affinity for the elements, O, S, F and Cl is:
1. | Cl < F < O < S | 2. | O < S < F < Cl |
3. | F < S < O < Cl | 4. | S < O < Cl < F |
The electron gain enthalpies of halogens in kJ mol-1 are given below.
F =-332, Cl =-349, Br =-325, I =-295.
The lesser negative value for F as compared to that of Cl is due to:
1. Strong electron-electron repulsions in the compact 2p-subshell of F.
2. Weak electron-electron repulsions in the bigger 3p-subshell of Cl.
3. Smaller electronegativity value of F than Cl.
4. 1 & 2 both
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. |
The incorrect match among the following is:
1. B < C < N < O (increasing first ionisation enthalpy)
2. I < Br < F < Cl (increasing electron gain enthalpy)
3. Li < Na < K < Rb (increasing metallic radius)
4. Al3+ < Mg2+ < Na+ <F- (increasing ionic size)
The correct order for electron affinity of halogens is :
1. Br > F
2. F > Cl
3. Br > Cl
4. F > I
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 |
Elements | |||
I | 520 | 7300 | -60 |
II | 419 | 3051 | -48 |
III | 1681 | 3374 | -328 |
IV | 1008 | 1846 | -295 |
V | 2372 | 5251 | +48 |
VI | 738 | 1451 | -40 |