Advertisements
Advertisements
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.
APPEARS IN
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 O has lower ΔiH than N and F?
How would you explain 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?
What are the various factors due to which the ionization enthalpy of the main group elements tends to decrease down a group?
Among the elements \[\ce{B, Al, C}\] and \[\ce{Si}\], which element has the highest first ionisation enthalpy?
Arrange the elements \[\ce{N, P, O}\] and \[\ce{S}\] in the order of increasing first ionisation enthalpy. Give reason for the arrangement assigned.
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)
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?
