Determine the element that has an electronic configuration: 1s2, 2s2, 2p6, 3s2, 3p6, 4s2.

In order to determine a chemical element by its electronic configuration, it is necessary to count the number of electrons at each level.

1s2 2s2 2p6 3s2 3p6 4s2 – on the 1st level 2 electrons, on the second 8, on the third 8, on the fourth 2 electrons. A total of 20 electrons.

The number of electrons is equal to the ordinal number of the element in the periodic table. At number 20 we have Ca (calcium). It is located in 4 periods, as indicated by 4 energy levels and has 20 electrons.