Multiple Choice
The form of oxygen that combines three oxygen atoms into each molecule is called ____.
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2. Atoms & Elements
The Atom
Multiple Choice
Calcium has an atomic number of 20 and an atomic mass of 40. Therefore, a neutral calcium atom must have:
A
40 protons, 20 neutrons, and 20 electrons
B
20 protons, 20 neutrons, and 40 electrons
C
20 protons, 20 neutrons, and 20 electrons
D
20 protons, 40 neutrons, and 20 electrons
Verified step by step guidance1
Identify the atomic number of calcium, which is 20. The atomic number represents the number of protons in the atom.
Recognize that a neutral atom has an equal number of protons and electrons. Therefore, the number of electrons in a neutral calcium atom is also 20.
Use the atomic mass (given as 40) to find the number of neutrons. The atomic mass is approximately the sum of protons and neutrons: \(\text{Atomic Mass} = \text{Protons} + \text{Neutrons}\).
Rearrange the formula to solve for neutrons: \(\text{Neutrons} = \text{Atomic Mass} - \text{Protons}\).
Substitute the known values: \(\text{Neutrons} = 40 - 20\), which gives the number of neutrons in the calcium atom.
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