- Sodium (Na) has 1 valence electron.

- Magnesium (Mg) has 2 valence electrons.

- Aluminum (Al) has 3 valence electrons.

- Silicon (Si) has 4 valence electrons.

- Phosphorus (P) has 5 valence electrons.

- Sulfur (S) has 6 valence electrons.

- Chlorine (Cl) has 7 valence electrons.

- Argon (Ar) has 8 valence electrons.

This trend is a result of the increasing atomic number of the elements. As we move from left to right, the number of protons in the nucleus increases by one for each element. This increase in the number of protons attracts more electrons to the nucleus, resulting in an increase in the number of valence electrons.

The number of valence electrons is important because it determines the chemical properties of an element. Elements with the same number of valence electrons tend to have similar chemical properties. For example, sodium, potassium, and cesium are all alkali metals with 1 valence electron. They all react in a similar way with other elements, such as forming +1 ions.