Multiple Choice
What is the mass number of the most abundant isotope of the element copper (Cu)?
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2. Atoms & Elements
Atomic Mass
Multiple Choice
Which of the following best describes the difference between atomic mass and atomic number?
A
Atomic mass is the number of protons, while atomic number is the total number of protons and neutrons.
B
Atomic mass is always equal to the atomic number for all elements.
C
Atomic mass is the total number of protons and neutrons in an atom, while atomic number is the number of protons.
D
Atomic mass is the number of electrons in an atom, while atomic number is the number of neutrons.
Verified step by step guidance1
Step 1: Understand the definition of atomic number. The atomic number is the number of protons in the nucleus of an atom. It uniquely identifies an element.
Step 2: Understand the definition of atomic mass. Atomic mass (or mass number) is the total number of protons and neutrons in the nucleus of an atom.
Step 3: Recognize that electrons have negligible mass compared to protons and neutrons, so they do not significantly affect atomic mass.
Step 4: Compare the two definitions: atomic number counts only protons, while atomic mass counts both protons and neutrons.
Step 5: Conclude that the correct description is: atomic mass is the total number of protons and neutrons in an atom, while atomic number is the number of protons.
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