`""_8X^16` and `""_8X^17` represent

Options

A. isotones
B. isobars
C. isotopes
D. isosters

Answer

To solve the question regarding the symbols `""_8X^16` and `""_8X^17`, we need to understand the concepts of atomic number, mass number, and isotopes.

### Step-by-Step Solution:

1. **Identify the Components**:
- The notation `""_8X^16` and `""_8X^17` can be broken down into two parts: the atomic number (the subscript) and the mass number (the superscript).
- Here, `8` is the atomic number, and `16` and `17` are the mass numbers.

2. **Understanding Atomic Number**:
- The atomic number (8) indicates the number of protons in the nucleus of the atom. This also defines the element, which in this case is oxygen (O), as oxygen has an atomic number of 8.

3. **Understanding Mass Number**:
- The mass number is the total number of protons and neutrons in the nucleus.
- For `""_8X^16`, the mass number is 16, which means it has 8 protons and (16 - 8) = 8 neutrons.
- For `""_8X^17`, the mass number is 17, which means it has 8 protons and (17 - 8) = 9 neutrons.

4. **Identifying Isotopes**:
- Isotopes are atoms of the same element (same atomic number) that have different mass numbers due to a different number of neutrons.
- Since both `""_8X^16` and `""_8X^17` have the same atomic number (8) but different mass numbers (16 and 17), they are isotopes of oxygen.

5. **Conclusion**:
- Therefore, `""_8X^16` and `""_8X^17` represent isotopes of the element oxygen.

### Final Answer:
`""_8X^16` and `""_8X^17` represent isotopes of oxygen.

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