Isotopes
Two or more atoms these neutron number is not same but proton number is same are isotopes of each other. Another definition of isotopes are atoms with same atomic number but different mass number. Mass number of an atom is the sum of proton number and neutron number. Proton number is the atomic number of an atom. If proton number is same in two different atom it is possible to find different mass number if the neutron number is different. If two or more atoms are found with same proton number but different mass number they are isotopes of each others. The most common example of isotope is carbon-12 and carbon-14. In both atom the proton number is 6 but mass number is different. Hence the neutron number is also different. Hence, carbon-12 and carbon-14 is isotope of each other. In carbon-12 isotope the neutron number is six but in carbon-14 isotope the neutron number is eight.The another important isotopes of hydrogen atom is hydrogen, deuterium and tritium. Oxygen also have isotopes. The isotopes of oxygen are found where the the mass number is respectively 16, 17 and 18. Chlorine-35 and chlorine-37 are the two isotopes of chlorine where the atomic number or proton number is same but mass number or neutron number is different.