Question

Use the periodic table and what you know about mass numbers to complete each statement.U-238 has protons and146 neutrons.A particular isotope of plutonium has 94 protons, neutrons, and a mass number of 241.Thorium- has 90 protons and 137 neutrons.

Answer 1

Let's break down the information provided and complete the statements regarding the isotopes.

1. **U-238** has 92 protons and 146 neutrons. Thus, the mass number of U-238 is the sum of the number of protons and neutrons:
\[
\text{Mass number} = \text{Protons} + \text{Neutrons} = 92 + 146 = 238
\]
So, U-238 is Uranium-238.

2. A particular isotope of plutonium has 94 protons, **neutrons** (we need to find this), and a mass number of 241.
Using the mass number to find neutrons:
\[
\text{Neutrons} = \text{Mass number} - \text{Protons} = 241 - 94 = 147
\]
Therefore, this isotope of plutonium is Plutonium-241 (Pu-241), which has 94 protons and 147 neutrons.

3. **Thorium-** (we need to find the mass number) has 90 protons and 137 neutrons.
Calculating the mass number:
\[
\text{Mass number} = \text{Protons} + \text{Neutrons} = 90 + 137 = 227
\]
Thus, this isotope of thorium is Thorium-227 (Th-227).

Here are the complete statements:

- U-238 has 92 protons and **146** neutrons.
- A particular isotope of plutonium has 94 protons, **147** neutrons, and a mass number of 241.
- Thorium-227 has 90 protons and **137** neutrons.