S1.2.2: Isotopes

 Isotopes 

• Same Element 

• Same Proton amount, atomic number 

• Different number of neutrons 

• Different mass number 

Protons –

decide element type 

Neutron –

change the mass 

Isotopes nearly have

identical chemical properties because chemical reactions depend on electron arrangement mostly.  

Isotopes (if neutral) have the same number of  

electrons so they form the same bonds and undergo the same type of reactions. 

Isotopes can have

different physical properties because their masses differ so this can impact measurable properties 

• Density 

• Melting and Boiling Point – small difference 

• Diffusion Rate 

 

Relative Abundance = 

 

the percentage of each isotope present in a naturally occurring sample 

 

Relative Atomic Mass 

• • Atomic masses on the periodic table are not usually whole numbers because they are a mixture of isotopes 

Relative Atomic Mass (Ar) 

Weighted average of the masses of an element’s isotopes based on their natural abundances, compared with 1/12 of the mass of carbon-12 atomic. No units