Question

electrons:
13.
p: 56
n: 81
mass number:
element name:
element symbol:

Explanation:

Step1: Recall Mass Number Formula

Mass number ($A$) is the sum of protons ($P$) and neutrons ($N$), so $A = P + N$.

Step2: Substitute Values

Given $P = 56$ and $N = 81$, calculate $A = 56 + 81 = 137$.

Step3: Identify Element from Protons

Proton number (atomic number, $Z$) is 56. The element with $Z = 56$ is Barium (Ba).

Answer:

Mass Number: $\boldsymbol{137}$
Element Name: Barium
Element Symbol: $\boldsymbol{Ba}$