Multiple Choice
What is the atomic number of potassium?
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2. Atoms & Elements
Atomic Mass
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What is the mass number of sodium?
A
24
B
11
C
22
D
23
Verified step by step guidance1
Understand that the mass number of an element is the total number of protons and neutrons in its nucleus.
Recall that the atomic number of sodium (Na) is 11, which represents the number of protons in the nucleus.
Use the periodic table to confirm that sodium has an atomic number of 11.
Recognize that the mass number is typically the nearest whole number to the atomic mass of the element as listed on the periodic table.
Check the periodic table for sodium's atomic mass, which is approximately 22.99, and round it to the nearest whole number to find the mass number.
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