In the periodic table, we can see some interesting patterns in how electrons are arranged. Let’s break it down into two main parts: periods and groups.

1. Periods: When you move from left to right in a period, the number of electrons goes up.

This means we're filling up the same energy level, or shell.

For example, in Period 2, we start with Lithium, which has one electron.

Then we go all the way to Neon, which has a full outer shell of six electrons.

2. Groups: Elements that are in the same group have similar arrangements of their outer electrons.

Take Group 1, for example, which includes alkali metals.

All the elements in this group have one electron in their outer shell.

For sodium, we can write its electron arrangement as $[Ne]3s^1$.

These patterns in electron configurations help us guess how different elements will behave in chemical reactions!