Question

what is the element? phosphorus silicon sulfur chlorine

Explanation:

Step1: Count the electrons

Count the number of electrons in each orbital: 2s has 2 electrons, 2p has 6 electrons, 3s has 2 electrons, 3p has 5 electrons.
$$2 + 6+2 + 5=15$$

Step2: Identify the element

The atomic number of an element is equal to the number of electrons in a neutral atom. Phosphorus has an atomic number of 15.

Answer:

Phosphorus