Question

PLEASE HELP Determine the number of neutrons for the given isotopes:

helium-3
carbon-14
nitrogen-15
strontium-90
tellurium-123

Answer 1

Helium = 1
Carbon = 8
Nitrogen = 8
Strontium = 52
Tellurium = 71

If you look on a periodic table, on each element there is a number on the top left. This represents the number of protons in an atom. Protons have a mass of 1 (in relative to Carbon-13)

If we take nitrogen-15 for example; The number 15 tells you that the isotope has a mass of 15. Now if you look on the periodic table, Nitrogen has a proton number of 7. Only protons and neutrons have a mass, electrons are considered to be negligable. Therefore the number of neutrons Nitrogen-15 contains is 15 - 7 = 8

Answer 2

Helium: 1

Carbon: 2

Nitrogen: 8

Strontium: 52

Tellurium: 71

Step-by-step explanation:

An isotope is atom that belongs to the same chemical element as another, has the same atomic number, but different atomic mass

So the data they give us is the mass number of the isotopes

A= mass number

Z= atomic number ( number of protons in the nucleus).

IS the number that appears in the periodic table

For example, the Z of neon is 10 and the Z of the oxygen is 8

m= number of neutrons

A= Z+ m

m=A-Z

Helium:

`m=A-Z\\ m=3-2\\m=1`

Carbon:

`m=A-Z\\ m=14-12\\m=2`

Nitrogen:

`m=A-Z\\ m=15-7\\m=8`

Strontium:

`m=A-Z\\ m=90-38\\m=52`

Tellurium:

`m=A-Z\\ m=123-52\\m=71`