The atomic mass of an element is the weighted average mass of the isotopes of that element. (true or false)
atoms with the same number of protons but different number of neutrons are called what? (choices: _isotopes, ions , iosomers)
how many neutrons are in potassium-40? the chemical symbol for potassium is k.
(choices: _19,20,21,40))

What element breaks down into yttrium-90?

Asample of ammonia reacts with oxygen as shown. 4nh3(g) + 5o2(g) 4no(g) + 6h2o(g) what is the limiting reactant if 4.0 g of nh3 react with 8.0 g of oxygen? o2 because it produces only 0.20 mol of no. nh3 because it produces only 0.20 mol of no. o2 because it produces two times less no than nh3. nh3 because it produces three times more no than o2.

How many moles of lead are in 1.50 x 10^12 atoms of lead? could you explain the answer as well and not just give it to me i am refreshing for finals and i need to know how to do it