Atomic masses
- Created by: sisi
- Created on: 15-03-13 18:41
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- Atomic Masses
- Relative Isotopic mass
- is the mass of an atom of an isotope compared with 1/12th of the mass of an atom of carbon-12
- All the atoms in a single isotope are identical. They all have the same mass measured against carbon 12
- For an isotope, the relative isotopic mass is the same as the mass number
- Relative atomic mass
- Is the weighted mean mass of an atom of an element compared with 1/12th of the mass of an atom of carbon -12
- Most elements contain a mixture of isotopes each in different amount and with a different mass.
- The contribution made by an isotope to the overall mass depends on
- the percentage abundance of the isotope
- the relative mass of the isotope
- The contribution made by an isotope to the overall mass depends on
- Relative molecular mass
- is the weighted mean mass of a molecule with 1/12th of the mass of an atom of carbon-12
- Many elements and compounds are made up of simple molecules such as O2 and CO2
- Relative formula mass
- is the weighted mean mass of a formula unit compared with 1/12th of the mass of an atom of carbon-12
- Compounds with giant structure do not exists as simple molecules for example NaCl
- Relative masses
- Atomic masses are measured in U(unified atomic mass unit)
- So the mass of 1/12th of an atom of carbon-12 is 1u
- Relative Isotopic mass
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