Valence Electrons Calculator

Valence electrons are the electrons in the outermost shell of an atom. They determine how an element bonds and reacts with other elements. Elements with the same number of valence electrons typically show similar chemical properties.

Valence electrons determine chemical reactivity, bonding capacity, and molecule formation. Elements gain, lose, or share valence electrons to achieve a stable electron configuration (usually 8 valence electrons - the octet rule).

Count electrons in the outermost shell (highest n value). For example, Na (1s² 2s² 2p⁶ 3s¹) has 1 valence electron in shell 3. O (1s² 2s² 2p⁴) has 6 valence electrons (2 + 4) in shell 2.

Yes, transition metals typically have 1-2 valence electrons in their outermost s orbital. However, they can also use d electrons from the next-lower shell in bonding, which is why they show variable oxidation states.

The octet rule states that atoms tend to gain, lose, or share electrons to achieve 8 valence electrons (like noble gases). Exceptions include H (wants 2), He (has 2), and some transition metals and larger atoms.

Noble gases (Group 18) have completely filled outer shells: He (2), Ne-Rn (8). This makes them extremely stable and unreactive. Other elements try to achieve this stable configuration through bonding.

Elements in period 3 and beyond can expand their octets and have more than 8 valence electrons using d orbitals. Examples: P in PCl₅ (10 electrons), S in SF₆ (12 electrons). Period 2 elements cannot exceed 8.