Multiple Choice
Which of the following elements has the same number of energy levels (principal shells) as nitrogen?
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2. Atoms & Elements
Periodic Table: Charges
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Which element on the periodic table has 20 protons in its nucleus?
A
Potassium
B
Sodium
C
Magnesium
D
Calcium
Verified step by step guidance1
Recall that the number of protons in the nucleus of an atom defines the atomic number of an element.
Identify the atomic numbers of the given elements: Potassium (K) has atomic number 19, Sodium (Na) has atomic number 11, Magnesium (Mg) has atomic number 12, and Calcium (Ca) has atomic number 20.
Match the atomic number 20 to the element with 20 protons, which is Calcium.
Understand that the atomic number uniquely identifies an element on the periodic table, so the element with 20 protons must be Calcium.
Therefore, the element with 20 protons in its nucleus is Calcium.
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