* Atomic Number: Sodium has an atomic number of 11, meaning it has 11 protons and 11 electrons.

* Electron Configuration:

* 1s² 2s² 2p⁶ 3s¹

* Explanation:

* 1s²: The first energy level (n=1) has 2 electrons in the 's' subshell.

* 2s²: The second energy level (n=2) has 2 electrons in the 's' subshell.

* 2p⁶: The second energy level (n=2) has 6 electrons in the 'p' subshell.

* 3s¹: The third energy level (n=3) has 1 electron in the 's' subshell.

Key Point: The single electron in the outermost 3s orbital is what makes sodium highly reactive and prone to losing an electron to form a positive ion (Na+).