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Multiple Choice
In basic atomic theory, what uniquely identifies (defines) a chemical element?
A
The number of electrons in a neutral atom
B
The number of protons in the nucleus (atomic number)
C
The atom's mass number (protons plus neutrons)
D
The number of neutrons in the nucleus
Verified step by step guidance
1
Understand that a chemical element is defined by a unique characteristic that distinguishes it from other elements.
Recall that atoms consist of protons, neutrons, and electrons, where protons and neutrons are in the nucleus, and electrons orbit around it.
Recognize that the number of protons in the nucleus is called the atomic number, and this number is unique for each element.
Note that while the number of electrons can vary in ions and the number of neutrons can vary in isotopes, the number of protons remains constant for a given element.
Therefore, the defining feature of a chemical element is its atomic number, which is the number of protons in the nucleus.