Multiple Choice
How many protons are present in the nucleus of an argon (Ar) atom?
1
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2. Atoms & Elements
The Atom
Multiple Choice
How many protons and electrons are present in a neutral atom of strontium (Sr)?
A
50 protons and 38 electrons
B
87 protons and 87 electrons
C
38 protons and 38 electrons
D
38 protons and 50 electrons
Verified step by step guidance1
Identify the atomic number of strontium (Sr) from the periodic table. The atomic number represents the number of protons in the nucleus of an atom.
Recall that in a neutral atom, the number of electrons equals the number of protons to balance the positive charge of the nucleus.
Look up the atomic number of strontium, which is 38. This means a neutral strontium atom has 38 protons.
Since the atom is neutral, it must also have 38 electrons to balance the charge of the 38 protons.
Conclude that a neutral atom of strontium contains 38 protons and 38 electrons.
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