To determine what element cesium-135 [tex]\(\left({ }_{55}^{135} Cs\right)\)[/tex] becomes after beta decay, we need to understand the process of beta decay itself.
Beta decay occurs when a neutron in the nucleus of an atom is transformed into a proton, and a beta particle (which is an electron) is emitted. This transformation increases the atomic number by 1, but the mass number remains unchanged because the number of nucleons (protons plus neutrons) does not change.
Given:
- Original element: Cesium (Cs) with an atomic number (Z) of 55 and a mass number (A) of 135.
During beta decay:
1. The atomic number will increase by 1.
2. The mass number will remain the same.
Therefore:
- The new atomic number will be 55 + 1 = 56.
- The mass number will remain 135.
Next, we use the periodic table to identify the element with an atomic number of 56. According to the periodic table, the element with atomic number 56 is Barium (Ba).
Putting it all together:
The cesium-135 [tex]\(\left({ }_{55}^{135} Cs\right)\)[/tex] becomes barium-135 [tex]\(\left({ }_{56}^{135} Ba\right)\)[/tex] after beta decay.
Therefore, the correct answer is:
D. [tex]\({ }_{56}^{135} Ba\)[/tex]
