Table of contents

2. Atoms & Elements

Ions

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Multiple Choice

A chlorine atom has 18 electrons and 17 protons. What is this atom called?

Chlorine cation (Cl^+)

Chloride ion (Cl^-)

Chlorate ion (ClO_3^-)

Neutral chlorine atom (Cl)

Verified step by step guidance

Identify the number of protons and electrons given: 17 protons and 18 electrons.

Recall that the number of protons defines the element. Since there are 17 protons, the element is chlorine (Cl).

Compare the number of electrons to the number of protons to determine the charge: more electrons than protons means a negative charge.

Calculate the charge by subtracting the number of protons from the number of electrons: 18 - 17 = 1 extra electron, so the charge is -1.

Conclude that the species is a chloride ion (Cl⁻), which is a chlorine atom with one extra electron.

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