When a sodium atom and a chlorine atom interact, the sodium atom tends to lose its outermost valence electron, while the chlorine atom tends to gain an electron to complete its outer shell. This transfer of electrons results in the formation of positively and negatively charged ions.

* Sodium atom: When a sodium atom loses its outermost valence electron, it becomes a positively charged ion known as a sodium ion (Na+). The loss of an electron leaves the sodium atom with an excess of protons in the nucleus compared to electrons, resulting in a net positive charge.

* Chlorine atom: When a chlorine atom gains an electron, it becomes a negatively charged ion known as a chloride ion (Cl-). The addition of an electron to the chlorine atom gives it an excess of electrons compared to protons, resulting in a net negative charge.

In summary, when a valence electron is transferred from a sodium atom to a chlorine atom, the sodium atom becomes a positively charged sodium ion (Na+), and the chlorine atom becomes a negatively charged chloride ion (Cl-).