Chemistry
Explain the trend in general of (i) electron affinity (ii) electronegativity of elements:
(a) on moving from left to right across a period
(b) on moving down a group.
Give reasons for the change in each periodic trend.
Answer
- Electron affinity
- Across a period atomic size decreases and nuclear charge increases. Both these factors lead to an increase in the Electron affinity across a period from left to right as a small atom with more nuclear charge can attract electrons more easily.
- On moving down a group both atomic size and nuclear charge increases but the increase in atomic size dominates over increase in nuclear charge hence Electron affinity decreases on moving down a group.
- Electronegativity
- Across a period atomic size decreases and nuclear charge increases. Both these factors lead to an increase in Electronegativity across a period from left to right as a small atom will pull the shared pair of electrons more than a large atom.
- On moving down a group both atomic size and nuclear charge increases but the increase in atomic size dominates over increase in nuclear charge hence Electronegativity decreases on moving down a group.
Related Questions
Give reasons for the following:
Atomic size of an element depends on the nuclear charge of that element.
Give reasons for the following:
Down a group electronegativity should increase with increase in nuclear charge but it is seen that the electronegativity decreases.
Give reasons for the following:
If combining atoms have nearly similar electronegativities the bond between them is covalent.
Arrange the following elements as per the guidelines in brackets.
- Na, Cl, Mg, P [in decreasing order of atomic size]
- C, Li, F, N [in increasing order of electronegativity]
- Cl, Al, Na, S [in increasing order of ionization potential]
- Li, F, C, O [in increasing order of electron affinity]
- Ar, He, Ne [in increasing order of number of electron shells]