The element calcium has the atomic number of 20 and the mass number of 40, how many neutrons does it have?

To an excellent approximation, is equivalent to nuclear mass; i.e. the combined mass of neutrons and protons. Can you tell us the identity of the nuclide? You have all the...

The most important thing to keep in mind here is that are atoms that have the same number of protons inside their nuclei. In other words, an isotope...

And $Z$ defines the identity of the element: $Z=1,H;Z=2,He;..........Z=6,C;........Z=37, Ru...........$ You don't have to remember these numbers, because a Periodic Table will be supplied to you in every test of...

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$"Moles of calcium"$ $=$ $(1200xx10^-3*g)/(40.08*g*mol^-1)$ $=$ $0.04008*mol$. And thus we need $0.04008*mol$ $"calcium carbonate"$, i.e. a mass of $0.04008*molxx100.09*g*mol^-1$ $=$ $??g$.

The weighted average of the is equal to $117.3*"amu"$. And thus.........with units of $"amu"$ $[65.43%xx119.8+34.57%xxchi] =117.3$ Where $chi-="mass of the other isotope"$.... And so we solve for $chi$.... $chi=(117.3-0.6543xx119.8)/(0.3457)=112.6*"amu"$

The answer is B) The must be exactly twice the for each atom. The number of protons is the atomic number of an element. The mass number is the sum...

What is the identity of this element? What is the isotope?

$Z$, $"the atomic number"$ of magnesium is 12. This means that there are 12 positively charged nuclear particles. This defines the particle as a magnesium atom. To represent the $""^24Mg$...

So we have the $"%calcium carbonate, "m/m$. We are not finished yet, because we have to address the percentage by mass of calcium metal in calcium carbonate: $%Ca=(40.08*g*mol^-1)/(100.09*g*mol^-1)=40%$ with respect...