Choose the element described by the following electron configuration. 1s22s22p63s23p64s1

Hey there.

By adding up all the "exponents," you'll get a number of 19. By looking at a periodic table, the element of such an atomic number is potassium or K.

Potassium

Explanation:

We are going to assume that this is an atom in it's ground state, not an ion.

Now let us count all the electrons

2 in the 1s orbital

2 in the 2s orbital

6 in the 2 p orbital

2 in the 3s orbital

6 in the 3p orbital

1 in the 4s orbital

Add them all up and we get 19. The element with 19 protons and hence 19 electrons in potassium

there are two significant figures.