Question

An isotope contains 15 protons, 15 electrons, and 17 neutrons. What is the identity of the isotope?

Answer 1

Answer: number of electrons= atomic number=15

                 therefore, it is phosporous

                                 whereas, proton+Neutron gives its mass=32

Explanation:

Answer 2

The identity of the isotope is Phosphorous(P).

• Isotopes are defined as the variations of chemical elements that possess the same number of protons and electrons, but a different number of neutrons.

Given:

No. of electrons(e-)=15

No. of Protons(p)=15

No. of Neutrons(n)=17

To Find:

Atomic Weight(Z)=?

Solution:

To find the atomic weight we have the formula:

$Z=p+n$

$Z=15+17$

$Z=32u$

Hence by the atomic weight Z=32u, the element is Phosphorous(P-32)

"*TRICK*/*SHORTCUT*"

• "The atomic number is always equal to the number of protons in it therefore, whenever asked about the identity of the isotope look at the numbers of protons."