Electron configuration is a way to describe where electrons are located around the center of an atom, called the nucleus.

Electrons are found in different energy levels, which we can think of as shells. Here’s how many electrons each shell can hold:

• 1st shell: can hold up to 2 electrons
• 2nd shell: can hold up to 8 electrons
• 3rd shell: can hold up to 18 electrons

Knowing how these electrons are arranged is really important. It helps us understand an element's chemical properties and where it fits in the periodic table.

Elements that are in the same group, or column, of the periodic table have similar electron configurations. This means they behave in similar ways.

For example, let's look at two elements: sodium (Na) and potassium (K).

• Sodium has the electron configuration of $1s^2 2s^2 2p^6 3s^1$.
• Potassium has $1s^2 2s^2 2p^6 3s^2 3p^6 4s^1$.

The difference is that potassium has one more electron than sodium. This extra electron makes potassium more reactive than sodium!

So, understanding electron configuration helps us see how and why different elements act the way they do.