To determine the number of atoms in 1.70ml of mercury, we have to determine the moles of mercury.
First find the mass in grams by using the formula:
Mass = volume x density
(1.70 mL Hg) x (13.5 g/mL) = 22.95 g Hg
Now find number of moles;
(22.95 g Hg) x (1 mol Hg/200.59 g/mol) = 0.1144 mol
Hg
For number of atoms multiply with Avogardro's number that is 6.023 x 10²³
(0.1144 mol Hg) x (6.023 x 10²³ atoms/mol) = 6.89
x 10²² atoms Hg
So, there is 6.89 x 10²² atoms of mercury are present in 1.70ml of mercury.