Question

the properties of valence electrons
an atoms valence electron shell
multiple choice

determines its atomic mass.

is the first shell to circle the nucleus.

is filled with positively charged particles.

always contains 8 electrons.

determines its chemical reactivity.

Explanation:

• "determines its atomic mass": Atomic mass is determined by protons and neutrons in the nucleus, not valence electrons.
• "is the first shell to circle the nucleus": The first shell (K - shell) is the innermost, while valence shell is the outermost (highest energy level) shell.
• "is filled with positively charged particles": Valence shell contains electrons (negatively charged), protons are in the nucleus.
• "always contains 8 electrons": Valence shell can have 1 - 8 electrons (e.g., H has 1, He has 2 in valence shell as it's a noble gas with full outer shell).
• "determines its chemical reactivity": Valence electrons are involved in chemical bonding and reactions, so the valence shell (and its electrons) dictates how an atom will react chemically.

Answer:

The option "determines its chemical reactivity." (the last option)