Multiple Choice
How many neutrons are in an atom of magnesium-25 ()? (Assume magnesium has atomic number .)
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4. Atoms and Elements
Isotopes
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Copper has two naturally occurring stable isotopes, and . Which statement correctly compares these two isotopes?
A
They have different numbers of protons but the same number of neutrons.
B
They have the same numbers of protons and neutrons but different numbers of electrons.
C
They have the same number of protons but different numbers of neutrons.
D
They have different numbers of protons and different chemical properties because they are different elements.
Verified step by step guidance1
Recall that isotopes of an element have the same number of protons but different numbers of neutrons.
Identify the element in question: Copper (Cu) has an atomic number of 29, which means every copper atom has 29 protons.
Look at the isotopes given: \(^{63}_{29}Cu\) and \(^{65}_{29}Cu\). The subscript (29) is the number of protons, which is the same for both isotopes.
The superscript (63 and 65) represents the mass number, which is the sum of protons and neutrons. Since the number of protons is 29, the number of neutrons is calculated by subtracting protons from the mass number: \(\text{neutrons} = \text{mass number} - \text{protons}\).
Therefore, \(^{63}_{29}Cu\) has \$63 - 29 = 34\( neutrons, and \)^{65}_{29}Cu\( has \)65 - 29 = 36$ neutrons, showing they have the same number of protons but different numbers of neutrons.
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