1. Calculate the moles of #"N"#.
Assume that we have 0.673 g of #"N"#.
Then we have 1 g of #"M"# and 1.673 g of #"M"_3"N"#.
#"Moles of N" = 0.673 color(red)(cancel(color(black)("g N"))) × "1 mol N"/(14.01color(red)(cancel(color(black)("g N")))) = "0.048 04 mol N""#
2. Calculate the moles of #"M"#.
There are three atoms of #"M"# for each atom of #"N"#, so there are three moles of #"M"# for each mole of #"N"#.
#"Moles of M" = 0.04804 color(red)(cancel(color(black)("mol N"))) × "3 mol M"/(1color(red)(cancel(color(black)("mol N")))) = "0.1441 mol M"#
3. Calculate the molar mass of #"M"#.
#"Molar mass" = "mass"/"moles" = "1 g"/"0.1441 mol" = "6.94 g/mol"# (3 significant figures)
4. Identify #"M"#.
The relative atomic mass is 6.94.
The metal with a relative atomic mass of 6.94 is lithium.
