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प्रश्न
Explain the following:
Ionisation enthalpy decrease in a group from top to bottom?
उत्तर
On moving down a group there is a gradual decrease in ionisation enthalpy. The decrease in ionisation enthalpy down a group can be explained in terms of net effect of the following factors:
(i) In going from top to bottom in a group, the nuclear charge increases.
(ii) There is a gradual increase in atomic size due to an additional main energy shell (n).
(iii) There is increase in shielding effect on the outermost electron due to increase in the number of inner electrons.
The effect of increase in atomic size and the shielding effect is much more than the effect of increase in nuclear charge. As a result, the electron becomes less and less firmly held to the nucleus as we move down the group. Hence, there is a gradual decrease in the ionization enthalpies in a group.
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संबंधित प्रश्न
Among the second period elements the actual ionization enthalpies are in the
order Li < B < Be < C < O < N < F < Ne.
Explain why Be has higher ΔiH than B?
Among the second period elements the actual ionization enthalpies are in the
order Li < B < Be < C < O < N < F < Ne.
Explain why O has lower ΔiH than N and F?
What are the various factors due to which the ionization enthalpy of the main group elements tends to decrease down a group?
The first ionization enthalpy values (in kJmol–1) of group 13 elements are:-
| B | Al | Ga | In | Tl |
| 801 | 577 | 579 | 558 | 589 |
How would you explain this deviation from the general trend?
Those elements impart colour to the flame on heating in it, the atoms of which require low energy for the ionisation (i.e., absorb energy in the visible region of spectrum). The elements of which of the following groups will impart colour to the flame?
(i) 2
(ii) 13
(iii) 1
(iv) 17
Nitrogen has positive electron gain enthalpy whereas oxygen has negative. However, oxygen has lower ionisation enthalpy than nitrogen. Explain.
Assertion (A): Generally, ionisation enthalpy increases from left to right in a period.
Reason (R): When successive electrons are added to the orbitals in the same principal quantum level, the shielding effect of inner core of electrons does not increase very much to compensate for the increased attraction of the electron to the nucleus.
Discuss and compare the trend in ionisation enthalpy of the elements of group1 with those of group17 elements.
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Which of the following atoms has the highest first ionization energy?
