Atoms bing because the become more stable when they have eight outer electrons
This is more of a physics explanation, but here we go.
Mass is a measure of how much "matter" is in an object. Weight is the force applied onto an object by gravity. Weight itself can be related to mass like this:

where g is a gravitational constant. For our purposes, it's defined by whatever planet you are on. Following this, we can demonstrate that mass is NOT the same thing as weight if we take two objects of the same mass and put them on different planets.
Let E refer to Earth and F refer to Mars

Following this, we can see clearly that weight is not the same as mass:

If weight was the same thing as mass, the two values would be the same, as the mass of the two objects is the same. But since weight is defined in the context of gravity, they are not.
Answer:
Isotopes – caused by varying numbers of neutrons in an element – have many practical uses in our society. ... In geology and archaeology, radioactive isotopes are used to determine the age of a sample while hydrologists can use isotope signatures to distinguish between different groundwater types.
Explanation:
Google. It's a magical place.
Answer:
1.26 x 10⁸pm³ and 1.26 x 10⁻²²cm³
Explanation: Calculating for a body centered cubic lattice, the formula is
3d²= 16r²
where d = edge length of unit cell
r=radius of atom
3d²= 16 x (217)²
3d²=753424
d²=251141.3
d= 501.1pm
volume of unit cell= d³= (501.1)³= 1.26 x 10⁸pm³
converting to cm³= 1.26 x 10⁸(10⁻¹²m)³
=1.26 x 10⁸(10⁻¹⁰cm)³ = 1.26 x 10⁻²²cm³