# How would you describe the structure ot an atom?

Sep 23, 2016

Up to GCSE it is a very small positive nucleus which has protons and neutrons, surrounded by negative electrons in shells or energy levels around it.

#### Explanation:

Protons have a charge of $+ 1$ and a relative mass of $1$
Neutrons are neutral (have no charge) and also have a mass of $1$
Electrons are negative (have a charge of $- 1$) and have a negligibly small relative mass $\left(\frac{1}{1840}\right)$

The first energy shell contains $2$ electrons and all the ones after that contain $8$.

Beyond GCSE we learn that electrons are arranged in 4 different orbitals named $s , p , d$ and $f$ which contain $2 , 6 , 10 \mathmr{and} 14$ electrons respectively.

The "first shell", known at A-level and beyond as the "principal quantum level" has a $s$ orbital (which means a maximum of $2$ electrons)

The second quantum level has $s \mathmr{and} p$ (which is a maximum of $2 + 6$ or $8$ electrons), the third has $s , p \mathmr{and} d$ (which means it has a maximum capacity of $18$) and the fourth has $s , p , d \mathmr{and} f$ (which means it has a maximum electron capacity of $32$).