A sample of unknown element X contains the following isotopes:
80% of 64X, 15% of 65x, and 5% of 66x. What is the average
atomic mass of element X?

number of molecules / avogadro's number * molecule molecular = mass

explanation:

we define a gram-molecular weight as the mass of one mole of any element or compound. a mole contains avogadro's number of units (molecules) –  

6.022

x

10

23

. so, dividing the number of molecules by avogadro's number gives us the number of moles. multiplying that by the molecular weight gives us the mass. from the periodic table we find the gram-molecular weight of u to be238 and of f to be19. so,  

u

f

6

will have a gram-molecular weight of 352g.

answer:

technetium is the most reactive. this is followed by silver. the least reactive out of these three elements is strontium.

answerca air mass;