In potassium atoms, how many protons are present?

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Multiple Choice

In potassium atoms, how many protons are present?

Protons determine an element’s identity; that count is the atomic number. Potassium is defined by atomic number 19, so a potassium atom has 19 protons. The proton count is fixed for an element, while neutrons can vary in isotopes (giving different mass numbers) and electrons can balance the charge in neutral atoms. If there were 18 protons, 20 protons, or 21 protons, you’d have a different element (argon, calcium, and scandium, respectively). So potassium contains 19 protons.

Protons determine an element’s identity; that count is the atomic number. Potassium is defined by atomic number 19, so a potassium atom has 19 protons. The proton count is fixed for an element, while neutrons can vary in isotopes (giving different mass numbers) and electrons can balance the charge in neutral atoms. If there were 18 protons, 20 protons, or 21 protons, you’d have a different element (argon, calcium, and scandium, respectively). So potassium contains 19 protons.

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