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Question
Which of the following statements are correct?
(i) Helium has the highest first ionisation enthalpy in the periodic table.
(ii) Chlorine has less negative electron gain enthalpy than fluorine.
(iii) Mercury and bromine are liquids at room temperature.
(iv) In any period, atomic radius of alkali metal is the highest.
Solution
(i) Helium has the highest first ionisation enthalpy in the periodic table.
(iii) Mercury and bromine are liquids at room temperature.
(iv) In any period, atomic radius of alkali metal is the highest.
Explanation:
He with 1s2 electronic configuration has the highest electron gain enthalpy in the periodic table.
In any period the alkali metals have lowest effective nuclear charge in that particular period for which its atomic radius is highest in that period.
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RELATED QUESTIONS
What is the significance of the terms - ‘isolated gaseous atom’ and ‘ground state’ while defining the ionization enthalpy and electron gain enthalpy?
Hint: Requirements for comparison purposes.
Which of the following pair of elements would have a more negative electron gain enthalpy?
F or Cl
Would you expect the second electron gain enthalpy of O as positive, more negative or less negative than the first? Justify your answer.
Describe the theory associated with the radius of an atom as it gains an electron.
Describe the theory associated with the radius of an atom as it loses an electron.
Which of the following pair of elements would have a more negative electron gain enthalpy?
O or F
Explain why the electron gain enthalpy of fluorine is less negative than that of chlorine.
Electronic configuration of some elements is given in Column I and their electron gain enthalpies are given in Column II. Match the electronic configuration with electron gain enthalpy.
| Column (I) | Column (II) |
| Electronic configuration | Electron gain enthalpy/kJ mol–1 |
| (i) 1s2 2s2 sp6 | (A) – 53 |
| (ii) 1s2 2s2 2p6 3s1 | (B) – 328 |
| (iii) 1s2 2s2 2p5 | (C) – 141 |
| (iv) 1s2 2s2 2p4 | (D) + 48 |
Assertion (A): Boron has a smaller first ionisation enthalpy than beryllium.
Reason (R): The penetration of a 2s electron to the nucleus is more than the 2p electron hence 2p electron is more shielded by the inner core of electrons than the 2s electrons.
Discuss the factors affecting electron gain enthalpy and the trend in its variation in the periodic table.
