To determine what particle X is in the reaction given, we need to analyze the nuclear reaction involving sodium (Na) and fluorine (F) along with helium (He). The reaction can be interpreted as follows: ### Step-by-Step Explanation 1. **Understanding the Reaction**: The reaction is presented as: \[ \text{Na} + X \rightarrow \text{F} + \text{He} \] Here, Na (sodium) is an element with an atomic number of 11 and a mass number of 23. Fluorine (F) has an atomic number of 9 and a mass number of 20, while helium (He) has an atomic number of 2 and a mass number of 4. 2. **Conservation of Mass and Charge**: In nuclear reactions, both mass number and atomic number must be conserved. This means that the total mass number and the total atomic number on the left side of the equation must equal those on the right side. - **Left Side**: - Sodium (Na): Atomic number = 11, Mass number = 23 - Particle X: Let’s denote its atomic number as \( Z_X \) and mass number as \( A_X \). - **Right Side**: - Fluorine (F): Atomic number = 9, Mass number = 20 - Helium (He): Atomic number = 2, Mass number = 4 **Total on the Right Side**: - Total Atomic Number = 9 (F) + 2 (He) = 11 - Total Mass Number = 20 (F) + 4 (He) = 24 3. **Setting Up the Equations**: From the conservation of atomic number: \[ 11 + Z_X = 9 + 2 \] Simplifying gives: \[ 11 + Z_X = 11 \implies Z_X = 0 \] From the conservation of mass number: \[ 23 + A_X = 20 + 4 \] Simplifying gives: \[ 23 + A_X = 24 \implies A_X = 1 \] 4. **Identifying Particle X**: The particle X has an atomic number of 0 and a mass number of 1. This corresponds to a neutron, which is a neutral particle (hence atomic number 0) and has a mass number of 1. ### Conclusion Thus, the correct answer is: **C. Neutron** ### Explanation of Other Options - **A. Alpha**: An alpha particle consists of 2 protons and 2 neutrons (essentially a helium nucleus). It has an atomic number of 2 and a mass number of 4. This does not fit our requirement of having an atomic number of 0. - **B. Beta**: A beta particle is an electron (or positron) emitted during radioactive decay. It has an atomic number of -1 (for electrons) or +1 (for positrons) and a mass number of 0. This does not match the characteristics of particle X. - **D. Gamma**: Gamma radiation is a form of electromagnetic radiation and has no mass or charge (atomic number 0, mass number 0). However, it does not account for the mass number conservation in this reaction. ### Revision Summary - In nuclear reactions, both mass number and atomic number must be conserved. - The particle X in the reaction is identified as a neutron, with atomic number 0 and mass number 1. - Alpha particles, beta particles, and gamma rays do not satisfy the conservation laws in this context. - Always check the conservation of mass and charge when analyzing nuclear reactions.