Answer
a. Mg and Cl
b. Mg and F
c. K and Cl
Work Step by Step
a. More favorable (more negative) electron affinity:
The electron affinity of an atom refers to the energy change that occurs when an atom gains an electron to form a negative ion. A more negative electron affinity indicates a stronger attraction for an additional electron.
In the first pair, (Mg and K), both elements are in Group 2 of the periodic table (alkaline earth metals) and Group 1 (alkali metals), respectively. Both elements have a tendency to lose electrons rather than gain them, so their electron affinities are generally low.
However, between Mg and K, K is an alkali metal with a single valence electron and very low electron affinity. Mg, though also low, is slightly more favorable.
From the second pair, Cl has a slightly more negative electron affinity than F due to less electron–electron repulsion in its larger 3p orbital.
b. Higher ionization energy:
Ionization energy refers to the energy required to remove an electron from an atom or ion in the gaseous state. Higher ionization energy indicates a stronger hold on the electrons.
In the pair (Mg and K), Mg (magnesium) has a higher ionization energy compared to K. This is because Mg has a smaller atomic size and a higher effective nuclear charge compared to K. The outermost electron in Mg experiences a stronger attraction to the nucleus, making it more difficult to remove compared to the outermost electron in K.
F is smaller and has a stronger hold on its electrons, requiring more energy to ionize.
c. Larger size:
The size of an atom refers to its atomic radius, which is the distance from the nucleus to the outermost electron. Larger size indicates a larger atomic radius.
In the pair (Mg and K), K has a larger size compared to Mg. This is because K is located in a higher period (row) of the periodic table compared to Mg. As we move down a group in the periodic table, the atomic size generally increases due to the addition of new electron shells. Therefore, K, being in a higher period, has a larger atomic radius compared to Mg.
Cl is in Period 3, while F is in Period 2. Atomic size increases down a group.
