# Using the periodic table, how would you determine the number of neutrons in 16 O?

Apr 4, 2017

Well the Periodic Table tells me UNEQUIVOCALLY, that the atomic number, $Z$, for oxygen is $8$, and thus the nucleus contains 8 neutrons.

#### Explanation:

How does this help us?

Well, we have the ""^16O isotope. The nucleus of the isotope contains 8 protons (i.e. $Z = 8$) unequivocally: this number of protons is what defines the element as an oxygen atom. But along with the 8 protons, the nucleus contains another 8 MASSIVE particles, i.e. 8 neutrons.......fundamental, massive $\text{nucular particles}$ of NEUTRAL charge; the sum of the massive particles, neutrons, and protons, $8 + 8 = 16$ gives the mass number of the isotope, which (as here) is commonly superscripted on the left of the element symbol. The ""^16O isotope is the common one, and is approx. 99.8% abundant (check this figure!).

""^17O, and ""^18O isotopes are the next most common isotopes. Can you tell me here (i) how many protons in each isotope; and (ii) how many neutrons in each isotope?

Apr 4, 2017

$8$ neutrons

#### Explanation:

the mass number is the number on the top-left of each element symbol that represents the sum of the number of protons and neutrons.
as stated in the question, this is $16$ for $16 O$.
the proton number is the number of protons and the number of electrons in the atom (not added together). this is on the bottom-left of each element symbol.
this is $8$ for oxygen, no matter the number of neutrons.
number of neutrons = mass number - proton number
$= 16 - 8$
$= 8$

therefore there are 8 neutrons.