Tin(ii) fluoride (snf2) is often added to toothpaste as an ingredient to prevent tooth decay. what is the mass of f in grams in 36.5 g of the compound?

From the periodic table:
molar mass of Sn = 118.71 grams
molar mass of F = 18.99 grams

This means that:
molar mass of SnF2 = 118.71 + 2(18.99) = 156.69 grams

Therefore, 156.69 grams of SnF2 contains 37.98 grams of F. To know the amount of F in 36.5 grams of the compound, we will simply do a cross multiplication as follows:
mass of F = (36.6 x 37.98) / 156.69 = 8.847 grams

☆ionisation energy increases across a period from na -> ar☆ionisation energy decreases down a group from li -> fr☆ionic radius decreases across a period from na -> cl☆ionic radius increases down a groupfrom f -> ii hope it clarifies your doubts