[Gary]

I am a little confused with the difference of the two...I have looked at multiple definitions for isotopes and the common theme is that the different number of neutrons is what defines an isotope. However, I have one chem book that defines an isotope as atoms with the same atomic number but different atomic mass, and I found various definitions that have phrases 'can have different number of neutrons' and similar.   Ions are when an atom's net charge changes due to a loss or gain of electrons.   

My confusion is as follows...If an isotope is defined by a change in its mass number, can this happen not from a different number of neutrons but a change in the number of electrons? and if so..is an Ion is a type of isotope.

Sorry for such a simple question, I'm not even done with Chapter 1 and I am confused with stuff like this.  : /

Gary

[Mitch]

An electron's mass is so much smaller than a neutron that it can be ignored for your purposes. An isotope of an element has more to do with a fix number of protons and neutrons and is less concerned with mass.

[organoman]

Don't get confused considering so many factors which are not needed. Try and grasp in following order.
1) An element is recognized only on the basis of number of protons irrespective of its mass number.
2)So if two atoms having same number of protons are actally same element.
3) Now question of isotope arises only if they are same element i.e. having same number of proton. So if number of protons are same and still mass number is different then atoms are isotopes.
4)Now same atomic number (number of proton) and different mass number actually means that number of neutrons are different as nucleus is chiefly constitutes of proton and neutron only.
 Number of electrons are not considered in this at all.
For example any element having number of proton i.e. atomic number 1 has to be an isotope of hydrogen
H - mass number 1(1 proton+0 neutron)
D - mass number 2(1 proton+1 neutron)
T- mass number 3 (1 proton+2 neutron)