# Question d0a6c

Nov 20, 2017

$\text{_17^37"Cl}$

#### Explanation:

For starters, take a look in the Periodic Table and find the atomic number of sulfur, $\text{S}$.

${Z}_{\text{sulfur}} = 16$

Since your unknown atom contains $1$ more proton than the sulfur-36 isotope, which contains $16$ protons inside its nucleus, you can say that you're dealing with the element that has

$Z = 16 + 1 = 17$

This element is chlorine, $\text{Cl}$, the element that follows sulfur in the Periodic Table.

Now, the number of neutrons present in the sulfur-36 isotope is given by the mass number of the isotope, $A$, and the atomic number of the element, $Z$.

$\textcolor{b l u e}{\underline{\textcolor{b l a c k}{\text{no. of neutrons" = "mass number " - " atomic number}}}}$

For the sulfur-36 isotope, you have

$\left\{\begin{matrix}A = 36 \\ Z = 16\end{matrix}\right.$

This means that this isotope contains

$\text{no. of neutrons} = A - Z$

$\text{no. of neutrons} = 36 - 16 = 20$

You can thus say that the chlorine isotope, which contains the same number of neutrons as the sulfur-36 isotope, will have a mass number equal to

$A = Z + \text{no. of neutrons}$

$A = 17 + 20 = 37$

This means that the unknown isotope is chlorine-37, one of two stable isotopes of chlorine. In isotope notation, which uses the atomic number, the mass number, and the chemical symbol of the element you can represent chlorine-37 as

""_17^37"Cl" -> {("mass number" = 37), ("atomic number" = 17) :}#