Question #5f5f9

Because atoms are so very, very small, it's very difficult for us to go directly from atoms to grams.

To make the transition easier, we use moles, which are simply very large groups of atoms. In order to have one mole of atoms you need to have #6.022 * 10^(23)# atoms #-># this is known as Avogadro's constant.

In your case, one mole of iron will contain #6.022 *10^(23)# atoms of iron. Now, the cool thing is that we know the mass of one mole of atoms of iron #-># this is known as iron's molar mass.

More specifically, iron is said to have a molar mass of #"55.845 g mol"^(-1)#, which means that one mole of iron has a mass of #"55.845 g"#.

At this point, our strategy will be to convert the number of atoms of iron to moles, then use the molar mass to convert the moles to grams

#2.58 * 10^(23) color(red)(cancel(color(black)("atoms Fe"))) * (1color(red)(cancel(color(black)("mole Fe"))))/(6.022 * 10^(23)color(red)(cancel(color(black)("atoms Fe")))) * "55.845 g"/(1color(red)(cancel(color(black)("mole Fe")))) = color(green)(bar(ul(|color(white)(a/a)color(black)("23.9 g")color(white)(a/a)|)))#

The answer is rounded to three sig figs.