Multiple Choice
Which property of an atom's model allows someone to identify the element it represents?
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2. Atoms & Elements
The Atom
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Which of the following describes a particle that contains 36 electrons?
A
A neutral atom of argon (Ar)
B
A neutral atom of krypton (Kr)
C
A K+ ion (potassium ion)
D
A Br- ion (bromide ion)
Verified step by step guidance1
Recall that the number of electrons in a neutral atom is equal to its atomic number, which is the number of protons in the nucleus.
Identify the atomic numbers of the elements involved: Argon (Ar) has atomic number 18, Krypton (Kr) has atomic number 36, Potassium (K) has atomic number 19, and Bromine (Br) has atomic number 35.
For ions, adjust the number of electrons based on the charge: a K+ ion has lost one electron, so it has 18 electrons; a Br- ion has gained one electron, so it has 36 electrons.
Compare the number of electrons for each species: a neutral Ar atom has 18 electrons, a neutral Kr atom has 36 electrons, a K+ ion has 18 electrons, and a Br- ion has 36 electrons.
Conclude that both a neutral krypton atom and a bromide ion (Br-) contain 36 electrons, but since the question asks for a particle with 36 electrons, the neutral krypton atom is the correct choice among the options given.
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