7: Relative formula mass Flashcards
What is relative atomic mass?
The relative atomic mass of an element compares the mass of atoms in the element with the mass of atoms of the 12C isotope. It is an average value of the isotopes of the element.
Its symbol is Ar
What is the Ar of common carbon atoms?
12
What if the Ar differs in carbon atoms?
Those below 12, have a lower mass than a carbon atom and those above 12, have a larger mass than a carbon atom.
How can you find relative atomic mass from the periodic table?
It is the top number next to the elements
What does the chemical formula of a substance tell you?
The number of each type of atom in a unit of that substane
What is the relative formula mass?
the mass of a unit of that substance compared to the mass of a carbon atom (Mr)
How do you work out relative formula mass?
By adding the Ar values for the atoms in the formula
