We must first determine the molar mass of iridium #("Ir")#, which is its relative atomic mass on the periodic table in g/mol.
The molar mass of #"Ir"## =##"192.217 g/mol"#.
#"1 mol Ir"=6.022xx10^23# atoms #"Ir"#
To determine the mass of #1.18xx10^26# atoms of #"Ir"#, divide the given number of atoms by #6.022xx10^23# atoms/mol to get moles of #"Ir"#, then multiply times the molar mass of #"Ir"# to get mass of #"Ir"# in grams.
#1.18xx10^26cancel"atoms Ir"xx(1cancel"mol Ir")/(6.022xx10^23cancel"atoms Ir")xx(192.217"g Ir")/(1cancel"mol Ir")=37700 "g Ir"# rounded to three significant figures.
