Structure of the Atom - Atomic Number and Mass Number

An atom of an element has $11$ protons and $12$ neutrons. Calculate its atomic number, mass number, and identify the element symbol in ${}_{Z}^{A}\text{X}$ notation.

Atomic Number ($Z$) = number of protons = $11$. Mass Number ($A$) = protons + neutrons = $11 + 12 = 23$. The element with $Z = 11$ is Sodium ($\text{Na}$). Symbol: ${}_{11}^{23}\text{Na}$.

The atomic number is directly equal to the proton count, while the mass number is the sum of nucleons (protons and neutrons).

The mass number of an element is $35$ and it contains $18$ neutrons. Find the number of electrons in the neutral atom and its atomic number.

$A = 35$, $n = 18$. Since $A = Z + n$, then $Z = A - n = 35 - 18 = 17$. For a neutral atom, number of electrons = $Z = 17$.

By subtracting the number of neutrons from the mass number, we obtain the atomic number. In a neutral state, the number of electrons matches this atomic number.

Calculate the number of protons, neutrons, and electrons in ${}_{6}^{14}\text{C}$.

From the notation ${}_{Z}^{A}\text{X}$, we have $Z = 6$ and $A = 14$. Protons ($p$) = $Z = 6$. Electrons ($e$) = $Z = 6$ (neutral atom). Neutrons ($n$) = $A - Z = 14 - 6 = 8$.

The subscript $6$ represents the number of protons, and the superscript $14$ represents the total number of protons and neutrons.