[Korokian]

atom A with 17 protons, 17 neutrons, and 17 electrons
and atom B with 17 protons, 18 neutrons, and 17 electrons
both atom A and atom B are isotopes correct?

[constant thinker]

Yes, isotopes have the same number of protons, but a different number of neutrons.

[Korokian]

oh okay thanks, i was just skeptic because i thought maybe 17 protons and neutrons couldn't be an isotope becuase it is a base element

so isotopes always come in pairs?

[Donaldson Tan]

isotopes don't always come in pair.

for example, for 1 proton, you have H (0 neutron), D (1 neutron) and T (2 neutrons).

[Borek]

isotopes don't always come in pair.

for example, for 1 proton, you have H (0 neutron), D (1 neutron) and T (2 neutrons).

Have you ever looked at the Periodic Table of Isotopes?

[english]

Any element you look at on the periodic table does not exist in one form.  The mass you see is actually an average of all its existing forms, or isotopes, in nature.  They don't always come in pairs, but several can exist for any one element.