Which of the following has the smallest atoms?
Different elements have atoms that weigh different amounts because there are different numbers of protons, neutrons, etc. If the weight is the same, the heavier elements will have fewer atoms.
Think of it as 1000 pounds of fat people will be less people than 1000 pounds of thin people.
I had this same problem during a practical exam. Thanks, now I know I have the right answer. Basically I took each 4.0g element and converted it to atoms/molecules.
1 mole = 6.022 x 10^23
For Li, Li has a molar mass of 6.941 grams, or 7 grams if you round up.
The longest path is therefore: 4.0 g Li x (1 mol/7 g Li) x (6.022 x 10^23 molecule / 1 mol Li)
grams and moles will cancel out and you will be left with the unit molecule/atoms, and now you multiply and divide and you should get…
Li= about 3.44 x 10^23 molecule/atoms
Now do this with the rest of the items and compare the results. C) Rb will be your answer.