* Valence electrons: These are the electrons in the outermost shell of an atom. They are the ones most likely to be involved in chemical bonding.
* Non-valence electrons: These are the electrons in inner shells. They are typically held more tightly to the nucleus and are less likely to participate in bonding.
What can influence an electron's potential to participate in bonding?
* Excitation: If an atom absorbs energy (like heat or light), a non-valence electron can be promoted to a higher energy level, potentially becoming a valence electron. This is a temporary state, and the electron will usually return to its ground state.
* Ionization: If an atom loses an electron, the remaining electrons in the outermost shell become valence electrons. This is a permanent change and creates an ion.
Example:
Consider a sodium atom (Na). It has one valence electron in its outermost shell. The inner shells contain non-valence electrons.
* Excitation: If sodium absorbs energy, one of its non-valence electrons can temporarily be excited to a higher energy level, becoming a valence electron. However, this state is unstable, and the electron will eventually fall back down, returning to its non-valence state.
* Ionization: If sodium loses its single valence electron, it becomes a sodium ion (Na+). Now, the electrons in the next inner shell are considered the valence electrons, even though they were originally non-valence electrons.
Important Note: The term "valence electron" is usually reserved for electrons in the outermost shell of an atom in its ground state. Electrons in excited or ionized states are not typically referred to as valence electrons, although they can participate in bonding in those states.
