Multiple Choice
Which is the correct isotope symbol for an atom with 42 protons and 49 neutrons?
42
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2. Atoms & Elements
Isotopes
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Given that the mass of the isotope Br-81 is 80.9163 amu, which statement is correct about Br-81?
A
Br-81 has 46 protons and 35 neutrons.
B
Br-81 has 35 protons and 46 neutrons.
C
Br-81 has 40 protons and 41 neutrons.
D
Br-81 has 81 protons and 0 neutrons.
Verified step by step guidance1
Identify the atomic number of bromine (Br) from the periodic table, which represents the number of protons in the nucleus of any bromine atom.
Recall that the atomic number of bromine is 35, so every bromine isotope has 35 protons.
Understand that the isotope number (mass number) is the sum of protons and neutrons in the nucleus, given here as 81 for Br-81.
Calculate the number of neutrons by subtracting the number of protons from the mass number: \(\text{neutrons} = 81 - 35\).
Use this information to verify which statement correctly matches 35 protons and the calculated number of neutrons for Br-81.
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