Is elemental copper a pure substance

As you move from right to left on the periodic table the atomic radius fill in the blank

Tin has ten stable isotopes. the heaviest, 124sn, makes up 5.80% of naturally occuring tin atoms. how many atoms of 124sn are present in 82.0 g of naturally occurring tin? what is the total mass of the 124sn atoms in this sample?

Do polar molecules have ionic bonds?