객관식
In which of the following atoms is the 2s orbital closest to the nucleus?
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2. Atoms & Elements
The Atom
Multiple Choice
An atom of calcium contains 20 protons. How many electrons does it have in its neutral state?
A
22
B
40
C
20
D
18
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검증된 단계별 안내1
Recall that in a neutral atom, the number of electrons equals the number of protons to balance the positive and negative charges.
Identify the number of protons in the calcium atom, which is given as 20.
Since the atom is neutral, set the number of electrons equal to the number of protons: \(\text{electrons} = 20\).
Understand that the mass number (such as 40 or 22) does not affect the number of electrons in a neutral atom; it relates to protons plus neutrons.
Conclude that the calcium atom has 20 electrons in its neutral state.
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