Which element is most likely to gain electrons in a chemical reaction?
1) kr
2) br
3) ca
4) ba

The correct answer to the question is Option 2. Br

Electronegativity is simply defined as the ability of an atom to attract electron(s)

Non metals are more electronegative than metals.

Krypton, Kr is a group 18 element which have completely filled outermost shell. They do not involve in bond formation.

Calcium, Ca and Barium, Ba are group 2 metals. They form bond by losing their 2 valence electrons.

Bromine, Br is a group 17 element which have 7 valence electrons. It is difficult for Br to lose its valence electron(s) and as such, it will form bond by either gaining 1 electron or sharing 1 electron.

With the above information, we can conclude that Option 2. Br gives the correct answer to the question.

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i'm pretty sure its b i might be wrong though!

the ratio of the conjugate base to the acid required to attain the desired ph.