Based on reference table s, the atoms of which of these elements have the strongest attraction for electrons in a chemical bond?
(1) n (3) p
(2) na (4) pt

Answer is (1) - N

Explanation:

I think the given chart is electronegativity chart.

Electronegativity is a value that tells us how an atom can attract electrons towards itself. If the electronegativity is high, then the attraction to the electrons is high unless the attraction to the electrons is low.

Electronegativity increases from left to right of the periodic table and decreases from up to down. 
Hence, highest electronegative atom is F which has 4.0 and lowest electronegative atoms are Cs and Fr (0.7).

The electronegativity values for given atoms are
  N - 3.0
  Na - 0.9
  P - 2.1
  Pt - 2.2