Advertisements
Advertisements
प्रश्न
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?
Advertisements
उत्तर १
On moving down a group, ionization enthalpy generally decreases due to an increase in the atomic size and shielding. Thus, on moving down group 13, ionization enthalpy decreases from B to Al. But, Ga has higher ionization enthalpy than Al. Al follows immediately after s–block elements, whereas Ga follows after d–block elements. The shielding provided by d-electrons is not very effective. These electrons do not shield the valence electrons very effectively. As a result, the valence electrons of Ga experience a greater effective nuclear charge than those of Al. Further, moving from Ga to In, the ionization enthalpy decreases due to an increase in the atomic size and shielding. But, on moving from In to Tl, the ionization enthalpy again increases. In the periodic table, Tl follows after 4f and 5d electrons. The shielding provided by the electrons in both these orbitals is not very effective. Therefore, the valence electron is held quite strongly by the nucleus. Hence, the ionization energy of Tl is on the higher side.
उत्तर २
The decrease in ∆iH1 value from B to Al is due to the bigger size of Al.
In Ga there is 10 3d electrons which do not screen as is done by S and P electrons. Therefore, there is an unexpected increase in the magnitude of effective nuclear charge resulting in increased ∆iH1 values. The same is with into Tl. The later has fourteen ∆f electrons with very poor shielding effect. This also increases, the effective nuclear charge thus the value of ∆iH1 increases.
संबंधित प्रश्न
Energy of an electron in the ground state of the hydrogen atom is –2.18 × 10–18 J. Calculate the ionization enthalpy of atomic hydrogen in terms of J mol–1.
Hint: Apply the idea of mole concept to derive the answer.
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?
Would you expect the first ionization enthalpies for two isotopes of the same element to be the same or different? Justify your answer.
Which one of the following statements is incorrect in relation to ionization enthalpy?
Among the elements \[\ce{B, Al, C}\] and \[\ce{Si}\], which element has the highest first ionisation enthalpy?
Nitrogen has positive electron gain enthalpy whereas oxygen has negative. However, oxygen has lower ionisation enthalpy than nitrogen. Explain.
Arrange the elements \[\ce{N, P, O}\] and \[\ce{S}\] in the order of increasing first ionisation enthalpy. Give reason for the arrangement assigned.
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.
Consider the elements Mg, Al, S, P and Si, the correct increasing order of their first ionization enthalpy is ______.
For the gaseous reaction, \[\ce{K_{(g)} + F_{(g)} -> K^+_{ (g)} + F^-_{ (g)}}\], ΔH was calculated to be 19 kcal/mol under conditions where the cations and anions were prevented by electrostatic separation from combining with each other. The ionisation energy of K is 4.3 eV. The electron affinity of F is ______. (in eV)
`"A"_0/2` atoms of X(g) are converted into X+(g) by absorbing energy E1. `"A"_0/2` ions of X+(g) are converted into X−(g) with release of energy E2. Hence ionization energy and electron affinity of X(g) are ______.
The decreasing order of the second ionization potential of K, Ca and Ba is ______.
Which of the following atoms has the highest first ionization energy?
