please tell me what they are because i cannot find a secure definition of any of them and then apparently relative atomic mass is the same as atomic weight or something? im confused please help.
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All relative masses are defined with respect to the one twelfth of the mass of one atom of the isotope carbon-12. This has 6 protons, 6 neutrons and 6 electrons. Consequently it is about the same as one atom of hydrogen-1 (which has one proton and 1 electron). Because they are 'relative' they have no units.
The relative isotopic mass is the mass of one atom of that isotope divided by one twelfth of the mass of one atom of carbon-12
The relative atomic mass of an element is the weighted average mass of atoms of that element divided by one twelfth of the mass of one atom of carbon-12. The atomic weight has the same numerical value as the relative atomic mass but has units of atomic mass units (amu), where 1 amu is the mass of 1 atom of carbon-12.
The relative molecular mass of a molecular substance is the weighted average mass of molecules of the substance divided by one twelfth of the mass of one atom of carbon-12
or
The relative molecular mass of a molecular substance is the sum of the relative atomic masses of the atoms which appear in the molecular formula of the substance.
Obviously, the relative molecular mass only applies to substances which exist as 'molecules', i.e. small groups of atoms connected by covalent bonds, e.g. O2, CO2, C2H6 but NOT substances which exist as giant structures such as KBr, SiO2, Fe.
The relative formula mass of a substance is the weighted average mass of formula units of the substance divided by one twelfth of the mass of one atom of carbon-12
or
The relative formula mass of a substance is the sum of the relative atomic masses of the atoms which appear in the stated formula of the substance,
The relative formula mass can apply to any substance which has a defined formula, e.g. H2, CH4, Ne, NaCl, C6H12O6, CaCO3, CuSO4.5H2O, Fe, etc
The relative isotopic mass is the mass of one atom of that isotope divided by one twelfth of the mass of one atom of carbon-12
The relative atomic mass of an element is the weighted average mass of atoms of that element divided by one twelfth of the mass of one atom of carbon-12. The atomic weight has the same numerical value as the relative atomic mass but has units of atomic mass units (amu), where 1 amu is the mass of 1 atom of carbon-12.
The relative molecular mass of a molecular substance is the weighted average mass of molecules of the substance divided by one twelfth of the mass of one atom of carbon-12
or
The relative molecular mass of a molecular substance is the sum of the relative atomic masses of the atoms which appear in the molecular formula of the substance.
Obviously, the relative molecular mass only applies to substances which exist as 'molecules', i.e. small groups of atoms connected by covalent bonds, e.g. O2, CO2, C2H6 but NOT substances which exist as giant structures such as KBr, SiO2, Fe.
The relative formula mass of a substance is the weighted average mass of formula units of the substance divided by one twelfth of the mass of one atom of carbon-12
or
The relative formula mass of a substance is the sum of the relative atomic masses of the atoms which appear in the stated formula of the substance,
The relative formula mass can apply to any substance which has a defined formula, e.g. H2, CH4, Ne, NaCl, C6H12O6, CaCO3, CuSO4.5H2O, Fe, etc