Consider four atoms from the second period: lithium, beryllium boron carbon and nitrogen which of these element has the lowest electronegativity value?

Answer is: lithium.

Electronegativity (χ) is a property that describes the tendency of an atom to attract a shared pair of electrons.

Electronegativity increases from left to right across a period.  

Atoms with higher electronegativity attracts more electrons towards it, electrons are closer to that atom.

For example nitrogen has electronegativity approximately χ = 3 and lithium has χ = 1, so if they form bond, nitrogen will have negative and lithium positive charge.

the correct answer to this question is 2