There are three isotopes of hydrogen: hydrogen ... They have the same mass number, A, but different atomic number, Z, and different chemical symbol - they are not the same element.

frac{mass~of~an~element~in~the~compound}{relative~formula~mass~M_r} \times 100\) There are six atoms of hydrogen in the compound, so the mass of hydrogen is 6 × 1 = 6. \({\%~of~hydrogen} ...

The size of the atoms and their mass has a lot to do with the density of the substance Another factor is how the atoms are arranged in the substance. Polyethylene is made up only of carbon and ...