what has the greatest ionic radius?\nbr\nk\ncl\nar\nwhat has the greatest electronegativity?\nbr\nkr\ncl\nar\…

Brief Explanations:

1. Ionic Radius: For the first "What has the greatest ionic radius?" among Br⁻, K⁺, Cl⁻, Ar, Br⁻ has the greatest ionic radius. Anions are larger than cations and neutral atoms of similar - period elements. Among the anions, Br⁻ is in a lower period than Cl⁻, so it has more electron - shells and a larger radius.
2. Electronegativity: Among Br, Kr, Cl, Ar, Cl has the greatest electronegativity. Electronegativity increases across a period from left to right and decreases down a group. Kr and Ar are noble gases and have very low electronegativities. Cl is above Br in the same group, so it has a higher electronegativity.
3. Atomic Radius: Among Mg, Ca, Na, K, K has the greatest atomic radius. Atomic radius increases down a group and decreases across a period. K is in a lower period than Na and in the same group as Na (Group 1), and Ca and Mg are in Group 2. Since elements in Group 1 have larger atomic radii than those in Group 2 in the same period and K is in a lower period than Ca, K has the largest atomic radius.
4. Ionic Radius (second question): Among Mg²⁺, Ca²⁺, Na⁺, K⁺, K⁺ has the greatest ionic radius. Cations in the same group increase in size as you go down the group due to the addition of electron - shells.

Answer:

1. Br
2. Cl
3. K
4. K