How many protons are in oxygen-18?
${ }_8^{18} O
A. 8
B. 10
C. 18
Answer (2)
The number of protons in an atom is given by its atomic number.
In the notation 8 18 O , the atomic number is 8.
Therefore, oxygen-18 has 8 protons.
Explanation
Understanding Atomic Structure The problem asks us to determine the number of protons in oxygen-18, which is represented as 8 18 O . In this notation, the subscript (8) is the atomic number, and the superscript (18) is the mass number. The atomic number defines the element and corresponds to the number of protons in the nucleus of an atom of that element.
Identifying the Number of Protons The atomic number of oxygen-18 is 8. The atomic number represents the number of protons in the nucleus of an atom. Therefore, oxygen-18 has 8 protons.
Final Answer Thus, the number of protons in oxygen-18 is 8.
Examples
Understanding the number of protons in an atom is crucial in many real-world applications. For example, in nuclear medicine, radioactive isotopes like oxygen-15 (7 protons, 8 neutrons) are used in PET scans. Knowing the number of protons helps scientists predict how these isotopes will decay and interact with the body, ensuring accurate diagnoses. Similarly, in environmental science, isotopes like carbon-14 (6 protons, 8 neutrons) are used to date organic materials. The number of protons helps determine the element and its chemical properties, which is essential for understanding its behavior in different environments.
Oxygen-18 has 8 protons, as indicated by its atomic number which is 8 in the notation 8 18 O . Therefore, the correct answer is A. 8.
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