Use the periodic table to identify the element with the following electron configuration: a. 1s2 2s2 2p6 3s2 enter the symbol of the elementb. krypton 5s2 4d6 enter the symbol of the elementc. how many unpaired electrons are present in a ground-state atom from the halogen family: enter a number, such as 0, 1, 2, etcd. unpaired electrons in the 5a column: enter a number, such as 0, 1, 2, etce. unpaired electrons in the 6b column enter a number, such as 0, 1, 2, etc