Question

how many valence electrons?
1s²2s²2p⁶3s²3p⁶4s²3d¹⁰4p⁶5s²4d¹⁰5p⁶6s²4f¹⁴5d²

Explanation:

Step1: Identify valence shell

Valence electrons are in the outermost shell. Here, the outermost shells are \(6s\), \(4f\), \(5d\).

Step2: Sum electrons in valence shell

The electron configuration for the outermost shells is \(6s^{2}4f^{14}5d^{2}\). Sum the exponents: \(2 + 14+ 2\).
$$2+14 + 2=18$$

Answer:

\(18\)