Sodium and magnesium are in the same period of the periodic table because they both belong to Period 3, which is characterized by having three electron shells. Sodium has an atomic number of 11, which means it has 11 electrons arranged in the electronic configuration of 1s² 2s² 2p⁶ 3s¹. Magnesium, with an atomic number of 12, has 12 electrons with the configuration of 1s² 2s² 2p⁶ 3s². Both elements have their outermost electrons in the third energy level, which defines their placement in Period 3.

Sodium and magnesium are located in Period 3 of the periodic table due to their electron configurations. This period is defined by elements that have three electron shells. Let's break down their characteristics:

Electron Configuration

Sodium (Na) has an atomic number of 11, which means it contains 11 electrons. Its electron configuration is:

• 1s² 2s² 2p⁶ 3s¹

This shows that sodium has one electron in its outermost shell (the third shell).

Magnesium's Structure

Magnesium (Mg), with an atomic number of 12, has 12 electrons. Its electron configuration is:

• 1s² 2s² 2p⁶ 3s²

Here, magnesium has two electrons in its outermost shell, also in the third energy level.

Why They Are in the Same Period

Both sodium and magnesium have their outermost electrons in the third shell, which is why they are grouped together in Period 3. This shared characteristic influences their chemical properties and reactivity.

Summary

In summary, sodium and magnesium are in the same period because they both have three electron shells, with their outermost electrons occupying the third energy level. This arrangement is fundamental to their classification in the periodic table.