Multiple Choice
Which of the following best describes how ions differ from atoms?
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2. Atoms & Elements
Ions
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How many electrons are present in a P^{2+} ion?
A
13
B
17
C
13
D
15
Verified step by step guidance1
Identify the atomic number of phosphorus (P), which represents the number of protons and, in a neutral atom, also the number of electrons. For phosphorus, the atomic number is 15.
Understand that the P^{2+} ion means the phosphorus atom has lost 2 electrons, resulting in a positive charge of +2.
Calculate the number of electrons in the P^{2+} ion by subtracting the charge (number of lost electrons) from the number of electrons in the neutral atom: $15 - 2$.
Write the expression for the number of electrons in the ion: $\text{electrons} = Z - \text{charge}$, where $Z$ is the atomic number.
Conclude that the P^{2+} ion has fewer electrons than the neutral atom by 2, so the total number of electrons is the atomic number minus 2.
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