# If we are converting phosphorus from 3.44 moles to atoms, why do we sometimes do mole -> atoms? Instead of doing moles -> molecules -> atoms?

Sep 12, 2016

Phosphorus can occur as a molecules ${P}_{8}$ in that case convert to molecules, but Phosphorus is an element and can also occur as a single atom as in the case for most elements.

#### Explanation:

Phosphorus is an element. Elements are usually converted from moles to atoms using Alvogardo's number $6.02 \times {10}^{23}$ If phosphorus is in elemental form it is not necessary to convert to molecules before changing to atoms.

Phosphorus can occur as an eight sided molecules. If the number of 3.44 moles is the number of ${P}_{8}$ then multiple $3.44 \times 6.02 \times {10}^{23}$

This gives the number of molecules of ${P}_{8}$ which then has to be multiplied by 8 to find the number of atoms.

It is important to note that normally the simple conversion of moles directly to atoms is the correct method.

Don't convert to molecules first unless directed to do so in the problem, as Phosphorus does not always occur in the molecular form as some elements like Hydrogen ${H}_{2}$ and Nitrogen ${N}_{2}$ do.