Multiple Choice
Element M has two naturally occurring isotopes: M-24 (abundance: 78.99%, mass: 23.985 amu) and M-25 (abundance: 21.01%, mass: 24.986 amu). What is the average atomic mass (in amu) of element M?
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2. Atoms & Elements
Atomic Mass
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Join thousands of students who trust us to help them ace their exams!Watch the first videoMultiple Choice
Which of the following best describes what the whole numbers on the periodic table represent?
A
The number of protons in the nucleus of an atom (atomic number)
B
The average atomic mass of the element
C
The total number of electrons in a neutral atom
D
The number of neutrons in the nucleus of an atom
Verified step by step guidance1
Understand that the whole numbers on the periodic table are called the atomic numbers.
Recall that the atomic number represents the number of protons in the nucleus of an atom, which uniquely identifies each element.
Recognize that the average atomic mass is a decimal number reflecting the weighted average of isotopes, not a whole number.
Know that the total number of electrons in a neutral atom equals the atomic number, but the periodic table specifically lists the atomic number (protons), not electrons.
Remember that the number of neutrons varies among isotopes and is not represented by the whole number on the periodic table.
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