Periodic trends: radius, ionisation enthalpy, electron gain enthalpy, electronegativity
Why this is asked: Chlorine, not fluorine, has the most negative electron gain enthalpy in its group — fluorine's small size packs the incoming electron into an already-crowded 2p subshell, offsetting its higher electronegativity. Ionisation enthalpy also dips at boron (below Be) and at oxygen (below N), because removing an electron from a filled 2s² or half-filled 2p³ costs extra — the "always rises across a period" rule breaks at exactly these two points.
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Which of the following statements are true?
A. Unlike Ga, which has a very high melting point, Cs has a very low melting point.
B. On the Pauling scale, the electronegativity values of N and Cl are not the same.
C. Ar, , , and are all isoelectronic species.
D. The correct order of the first ionisation enthalpies of Na, Mg, Al and Si is Si > Al > Mg > Na.
E. The atomic radius of Cs is greater than that of Li and Rb.
Choose the correct answer from the options given below:
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Arrange the following elements in increasing order of electronegativity: N, O, F, C, Si.
Choose the correct answer from the options given below:
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Arrange the following elements in increasing order of first ionisation enthalpy: Li, Be, B, C, N.
Choose the correct answer from the options given below:
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