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chemistry igcse acapprinted 13 · PDF 13
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Deuterium (²H): Has 1 proton and 1 neutron. It's stable and used in some scientific applications.
Tritium (³H): Has 1 proton and 2 neutrons. It's radioactive and used in nuclear fusion research.
Percentage Abundance and Relative atomic mass (calculation)
To calculate the relative atomic mass of an element with multiple isotopes, we multiply the relative atomic
mass of one isotope by its percentage abundance and add this for all isotopes, then divide by 100
((Isotopic mass 1 x % Isotope 1 ) + (Isotopic mass 2 x %Isotope 2 ) )/ 100
Q. The table shows the relative abundance of the two naturally occurring atoms of lithium.
Atom
6
7
Relative abundance
10%
90%
Calculate the relative atomic mass of lithium to one decimal place.
Ans : (6 x 10) + (7 x 90 ) = 690 / 100 = 6.9
• Here is a list of important polyatomic ions and their charges which you must know.
Polyatomic Ion
Charge
Sulfate
-2
Carbonate
-2
Nitrate
-1
Hydroxide
-1
Phosphate
-3
Ammonium
+1