Among 10-9 g (each) of the following elements, which one will have the highest number of atoms? Element: Pb, Po, Pr and Pt
- Pr
- Pt
- Po
- Pb
Answer
(1) Pr
Solution
Number of atoms = mM NA
For the same mass m, the element with the smallest molar mass M has the most atoms.
Molar masses ( g mol-1): Pr (Z = 59) = 140.9; Pt (Z = 78) = 195.1; Pb (Z = 82) = 207.2; Po (Z = 84) = 209
Pr (praseodymium) has the highest number of atoms.
Answer: (1)