For the isotope 17O2-, the number of protons, neutrons, and electrons are:
a) 6 protons, 9 neutrons, and 6 electrons
b) 8 protons, 8 neutrons, and 8 electrons
c) 8 protons, 17 neutrons, and 8 electrons
d) 8 protons, 9 neutrons, and 10 electrons
e) 7 protons, 10 neutrons, and 10 electrons
The correct answer and explanation is :
The correct answer is d) 8 protons, 9 neutrons, and 10 electrons.
Let’s break down why this is the correct answer.
1. Understanding the Isotope Notation:
The isotope is given as 17O2-. In this notation:
- O stands for oxygen.
- The number “17” represents the mass number (the sum of protons and neutrons) of the isotope.
- The “2-” signifies that the atom has gained two extra electrons, meaning it has a negative charge of 2.
2. Number of Protons (Atomic Number):
- Oxygen (O) has an atomic number of 8, meaning it has 8 protons. The atomic number is always equal to the number of protons in an element.
3. Number of Neutrons:
- The mass number of this isotope is 17. The mass number is the sum of protons and neutrons.
- To calculate the number of neutrons, subtract the number of protons from the mass number:
[
\text{Neutrons} = \text{Mass Number} – \text{Protons} = 17 – 8 = 9
] - Therefore, this isotope has 9 neutrons.
4. Number of Electrons:
- The neutral form of oxygen would have the same number of electrons as protons, so in a neutral oxygen atom, the number of electrons would be 8.
- However, the 2- charge indicates that the atom has gained two extra electrons, so the number of electrons is:
[
\text{Electrons} = 8 \, (\text{protons}) + 2 = 10
] - Therefore, this isotope has 10 electrons.
5. Summary:
- The 17O2- isotope has:
- 8 protons (since it’s oxygen),
- 9 neutrons (17 – 8 = 9),
- 10 electrons (due to the 2- charge).
Thus, the correct answer is d) 8 protons, 9 neutrons, and 10 electrons.