Multiple Choice
Which of the following best describes the formation of a cation?
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2. Atoms & Elements
Ions
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Which of the following is the correct formula for a potassium ion that has 18 electrons?
A
K^+
B
K^−
C
K
D
K^2+
Verified step by step guidance1
Step 1: Identify the atomic number of potassium (K). Potassium has an atomic number of 19, which means it has 19 protons and, in its neutral state, 19 electrons.
Step 2: Understand that the number of electrons changes when an ion is formed. A potassium ion with 18 electrons has lost one electron compared to the neutral atom.
Step 3: Determine the charge of the ion by comparing the number of protons and electrons. Since there are 19 protons and 18 electrons, the ion has a net positive charge of +1.
Step 4: Write the correct ion notation. The potassium ion with 18 electrons is represented as $K^{+}$, indicating a +1 charge.
Step 5: Confirm that other options do not match the electron count or charge: $K^{-}$ would have gained an electron (20 electrons), $K$ is neutral (19 electrons), and $K^{2+}$ would have lost two electrons (17 electrons).
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