* Sodium (Na) does have a valency of +1. This means it tends to lose one electron to achieve a stable electron configuration.

* Magnesium (Mg), however, has a valency of +2. It tends to lose two electrons to achieve a stable electron configuration.

Let's break down why:

Valency refers to the number of electrons an atom gains, loses, or shares when forming chemical bonds. It's essentially a measure of an atom's combining capacity.

Sodium (Na) has an electronic configuration of 2, 8, 1. It has one electron in its outermost shell (the valence shell). By losing this one electron, it achieves the stable electron configuration of the noble gas neon (2, 8). This makes it highly reactive and prone to forming ionic bonds where it donates an electron.

Magnesium (Mg) has an electronic configuration of 2, 8, 2. It has two electrons in its outermost shell. By losing these two electrons, it achieves the stable electron configuration of the noble gas neon (2, 8). This makes it less reactive than sodium but still inclined to form ionic bonds by donating two electrons.

In summary:

* Sodium loses one electron to achieve a +1 valency.

* Magnesium loses two electrons to achieve a +2 valency.

Let me know if you'd like a deeper dive into the concept of valency or electron configuration!