Use the equation to answer the question.

Question

21H+ 21H→ 42H+energy


Which statement best describes the mass numbers of the atoms in the reaction?

(1 point)
Responses

There is one atom with a mass number of 2.
There is one atom with a mass number of 2.

There are two atoms with mass numbers of 1.
There are two atoms with mass numbers of 1.

There is one atom with a mass number of 1.
There is one atom with a mass number of 1.

There are two atoms with mass numbers of 2.
There are two atoms with mass numbers of 2.

Answer 1

To analyze the equation:

\[ 21H + 21H \rightarrow 42H + \text{energy} \]

In this reaction, we can break down the components:

1. The notation \( 21H \) indicates hydrogen isotopes, specifically deuterium (\( ^2H \)), which has a mass number of 2.
2. When two deuterium atoms combine, the product is \( 42H \), which indicates a heavier hydrogen isotope (\( ^4H \)) and has a mass number of 4.

So, in this reaction:

• The left side (reactants) has two atoms of \( ^2H \) (deuterium), each with a mass number of 2.
• The right side (products) has one atom of \( ^4H \) (a hydrogen isotope), with a mass number of 4.

Given this analysis, the best description of the mass numbers of the atoms in the reaction is:

There are two atoms with mass numbers of 2.