Multiple Choice
What typically happens when oppositely charged ions are present in close proximity?
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2. Atoms & Elements
Ions
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An ion has 105 electrons. Which of the following statements is true about its mass number?
A
The mass number is equal to the number of protons.
B
The mass number cannot be determined from the number of electrons alone.
C
The mass number is equal to 105.
D
The mass number is always greater than the number of electrons.
Verified step by step guidance1
Recall that the mass number (A) of an atom or ion is the total number of protons (Z) plus neutrons (N) in its nucleus, expressed as $A = Z + N$.
Understand that the number of electrons does not directly determine the mass number because electrons have negligible mass compared to protons and neutrons.
Recognize that the number of electrons in an ion is related to the number of protons and the ion's charge, but without knowing the element (which defines the number of protons) or the number of neutrons, the mass number cannot be found.
Note that the mass number is generally greater than the number of electrons because the nucleus contains protons and neutrons, both contributing to mass, while electrons contribute very little mass.
Conclude that from knowing only the number of electrons (105), it is impossible to determine the mass number without additional information about the element or its neutron count.
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