Question

use the periodic table in the tools bar to complete the electron configurations for the following elements: lithium (li): 1s^a2s^b a = b = done

Explanation:

Step1: Recall lithium's atomic number

Lithium has atomic number 3.

Step2: Determine electron - filling

Electrons fill orbitals starting from the lowest - energy ones. The 1s orbital can hold 2 electrons and the 2s orbital can hold 2 electrons. For lithium with 3 electrons, 2 electrons go in 1s and 1 electron goes in 2s.

Answer:

A = 2
B = 1