Which element has atomic number 11?

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Multiple Choice

Which element has atomic number 11?

Explanation:
Atomic number tells you how many protons are in the nucleus, and it uniquely identifies an element. For sodium, that count is 11, so it is the element with atomic number 11. In the periodic table, sodium is in the alkali metals group and has the electron configuration 2, 8, 1, which reflects its single valence electron and explains its characteristic reactivity. The other elements listed have more protons: magnesium has 12, aluminum 13, and silicon 14, so none match 11. Therefore, the element with atomic number 11 is sodium.

Atomic number tells you how many protons are in the nucleus, and it uniquely identifies an element. For sodium, that count is 11, so it is the element with atomic number 11. In the periodic table, sodium is in the alkali metals group and has the electron configuration 2, 8, 1, which reflects its single valence electron and explains its characteristic reactivity. The other elements listed have more protons: magnesium has 12, aluminum 13, and silicon 14, so none match 11. Therefore, the element with atomic number 11 is sodium.

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