| A | B |
|---|
| most of the mass of an atom | is found in the nucleus |
| carbon has an atomic number of 6 | it has 6 protons |
| Ernest | Rutherford |
| Rutherford suggested that | atoms are mostly empty space |
| Originally, elements in the PT were placed | in order of mass |
| Henry | Moseley |
| Moseley arranged the elements in order of | the amount of the positive charge in the nucleus |
| The modern PT places elements in order of | the number of protons in their atoms |
| The atomic number = the number of | protons |
| All the atoms of an element have | the same unique atomic number |
| The mass of an electron | is negligible |
| negligible means that something | is so small it can be ignored |
| The total number of protons and neutrons in an atom | is called its mass number |
| The sun converts hydrogen | into helium |
| If the number of protons 90 | the number of electrons is the same |
| The neutron number = | Mass number - atomic number |
