Isotopes

Isotopes are atoms of the same element with the same number of protons and different number of neutronsHydrogen has three isotopes: hydrogen-1 (1 proton, 0 neutrons), hydrogen-2 or deuterium (1 proton, 1 neutron) and hydrogen-3 or tritium (1 proton, 2 neutrons). They all have the same atomic number but different mass numbers.Isotopes are written with the mass number at the top left and the atomic number at the bottom left of the symbol, for example ³⁵₁₇Cl and ³⁷₁₇Cl. Chlorine-35 has 17 protons and 18 neutrons; chlorine-37 has 17 protons and 20 neutrons. Both have 17 electrons.Chemical properties: isotopes of an element have the same number of electrons and the same electronic configuration. Chemical reactions involve electrons, so isotopes react in the same way.Physical properties: isotopes have different masses, so properties that depend on mass, such as density and rate of diffusion, are slightly different.Worked example: how many neutrons are in an atom of ¹³₆C?neutrons = mass number – atomic number = 13 – 6 = 7