To determine the particle that completes the given nuclear equation:
[tex]\[
_{56}^{124} \text{Ba} \rightarrow \, _{55}^{124} \text{Cs} + \text{ ? }
\][/tex]
we need to understand the type of nuclear reaction occurring.
### Step-by-Step Solution:
1. Identify the Type of Reaction:
The transition from Barium-124 ([tex]\( _{56}^{124} \text{Ba} \)[/tex]) to Cesium-124 ([tex]\( _{55}^{124} \text{Cs} \)[/tex]) involves a change in the atomic number but not in the mass number. The atomic number decreases from 56 to 55, while the mass number remains 124.
2. Beta Decay Characteristics:
In beta decay, a neutron in the nucleus changes into a proton, and an electron (beta particle) is emitted. This type of decay is referred to as beta-minus (β⁻) decay:
- The atomic number of the element increases by 1 (because a neutron converts into a proton).
- The mass number remains the same (since a neutron is converted to a proton, and no nucleons are lost).
3. Reverse the Process for Beta-Minus Decay:
To attain Cesium-124 from Barium-124 with a decrease in atomic number by 1, an electron (beta particle) must have been emitted.
The emitted particle during this type of decay is represented as:
[tex]\[
_{-1}^{0} \text{e}
\][/tex]
4. Balancing the Nuclear Equation:
By emitting this beta particle, the reaction maintains the balance in mass and charge:
[tex]\[
_{56}^{124} \text{Ba} \rightarrow \, _{55}^{124} \text{Cs} + _{-1}^{0} \text{e}
\][/tex]
### Final Answer:
The particle that completes the nuclear equation is:
[tex]\[
_{-1}^{0} \text{e}
\][/tex]
Thus, the correct answer is:
[tex]\[
\boxed{\,_{-1}^{0} \text{e}\,}
\][/tex]
