How many of the elements in the second row of the periodic table (Li through Ne) will have at least one unpaired electron in their electron configurations?

Answer 1

Write the electron configuration for each element and then select your answers based on the given criteria. I will write the configuration for the first 3 elements in period 2 and then you can complete the rest.

₃Li 1s²2s¹ - one unpaired electron

₄Be 1s²2s² - no unpaired electron

₅B 1s²2s²2p¹ - one unpaired electron

With elements B to Ne, you have to keep in mind that there are three p atomic orbitals that can hold a maximum of 6 electrons. When placing electrons in them, you have to first place them unpaired and then start pairing them as the # of electrons increase.