Elements in group 7A in the periodic table are called the halogens: elements in group 6A are called the chalcogens (a)
What is the most common oxidation state of the chalcogens compared to the halogens? (b) For each of the following
periodic properties. state whether the halogens or the chalcogens have larger values: atomic radii, ionic radii of the most
common oxidation state, first ionization energy. second ionization energy.

Chalcogens have −2, +2, +4, and +6 whereas halogens have −1, +1, +3, +5, and +7 oxidation state.

The most common oxidation states of the elements of chalcogens are −2, +2, +4, and +6 while on the other hand,  the oxidation states of halogens such as fluorine, chlorine, bromine, and iodine are −1, +1, +3, +5, and +7. The chalcogens have larger atomic as well as ionic radii as compared to halogens because of the presence of less number of electrons in the outermost shell.

We know that when we moves from left to right in the periodic table, atomic radius decreases due to addition of extra electrons in the outermost shell. The attraction of nucleus on the additional electron increases which leads to movement of outermost shell nearer to nucleus.

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Most common oxidation state of the chalcogens is -2, most common oxidation state of the halogens is -1.

Explanation:

For atomic radii, the chalcogens have a larger atomic radii than the halogens

This is because atomic radii decreases across the period due to increase in nuclear charge.

For ionic radii the chalcogens also have larger ionic radii than the halogens. This is because the chalcogens always carry a -2 charge compared to halogens that carry a -1 charge. Since -2 is the most common oxidation state for chalcogens and -1 is the most common oxidation state for the halogens.

In terms of oxidation states, the halogens show a higher value of common oxidation state -1 while for chalcogens is -2 even though +2, +4 and +6 oxidation states are also well known.

First ionization energy of halogens is greater than that of the chalcogens due to greater effective nuclear charge.

The second ionization energy of chalcogens is greater than that of the halogens.