#### Answer

$80,000$ hydrogen atoms weigh $1.336 \times 10^{-19}$ gram

#### Work Step by Step

Let x be the mass of 80,000 hydrogen atoms
Mass of one hydrogen atom = $1.67 \times 10^{-24}$ gram
Write the statement $80,000$ hydrogen atoms in scientific notation to obtain:
$$8 \times 10^{4}$$
Solve for $x$:
$x (gram) = 8 \times 10^{4} atoms \times \frac{1.67 \times10^{-24} gram}{1 atom}$
Recall the multiplication of numbers in scientific notation: $(a\times10^{n})(b\times10^{m}) = (a\times b) \times 10^{n+m}$
Thus,
$$x(gram) = (8\times1.67) \times 10^{4+(-24)}$$
$$x(gram) =13.36 \times 10^{-20}$$
$80,000$ hydrogen atoms weigh $1.336 \times 10^{-19}$ gram