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

2 Answers
Apr 4, 2017

Answer:

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 #"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

Answer:

#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 #16O#.
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.