Question

which metalloid has three valence electrons?
○ boron
○ arsenic
○ silicon
○ lithium

Explanation:

1. First, recall the definitions: Metalloids have properties between metals and non - metals. Valence electrons are the outermost electrons of an atom.
2. Analyze each option:

• Boron (B): Boron is a metalloid. Its electron configuration is $1s^{2}2s^{2}2p^{1}$, so it has 3 valence electrons.
• Arsenic (As): Arsenic is a metalloid, but its electron configuration gives it 5 valence electrons.
• Silicon (Si): Silicon is a metalloid with 4 valence electrons.
• Lithium (Li): Lithium is a metal, not a metalloid.

Answer:

A. boron