Question

use the periodic table to determine what element cesium - 135 ($_{55}^{135}$cs) becomes after beta decay.
a. $_{55}^{135}$cs
b. $_{53}^{131}$i
c. $_{57}^{139}$la
d. $_{56}^{135}$ba
e. $_{54}^{135}$xe

Explanation:

Step1: Recall beta - decay process

In beta - decay, a neutron in the nucleus is converted into a proton, an electron (beta - particle), and an antineutrino. The mass number ($A$) remains the same and the atomic number ($Z$) increases by 1.

Step2: Identify initial values

For cesium - 135 ($^{135}_{55}\text{Cs}$), the mass number $A = 135$ and the atomic number $Z=55$.

Step3: Determine new element

After beta - decay, the mass number stays $A = 135$, and the atomic number becomes $Z=55 + 1=56$. Looking at the periodic table, the element with atomic number 56 is barium (Ba), so the resulting element is $^{135}_{56}\text{Ba}$.

Answer:

D. $^{135}_{56}\text{Ba}$