Sodium (Na) has valence electrons because of its electron configuration and its position in the periodic table.
Sodium has an atomic number of 11, which means it has 11 electrons. The electron configuration of sodium is 1s² 2s² 2p⁶ 3s¹.
In the electron configuration, the first shell (n = 1) can hold a maximum of 2 electrons, and the second shell (n = 2) can hold a maximum of 8 electrons.
The valence electrons are the electrons in the outermost shell, which is the third shell (n = 3) for sodium. In this case, the valence electrons of sodium are only 1 electron, which is located in the 3s orbital.
Valence electrons are important because they determine an atom's chemical properties and how it can interact with other atoms to form chemical bonds. In the case of sodium, the single valence electron is relatively loosely held, making sodium highly reactive and prone to losing that electron to achieve a stable electron configuration.