How can atomic number and mass number be used to find the numbers of protons, electrons, and neutrons?
The atomic number is assigned based on the number of protons, so the atomic number is always the same as the number of protons
Atomic mass is the sum of protons and neutrons. Protons and neutrons both have masses of 1 amu, but the mass of electrons is negligible so it is left out. The atomic mass of an element is never a round number because it's a weighted average of all the isotopes of the element. Just round the number to the nearest integer get the most likely atomic mass.
In a neutral atom number of protons = number of electrons since there is no overall charge. In an ion, add an electron for every negative charge and subtract an electron for every positive charge (ex.
The atomic number of O is 8 and the mass number is ~16
So it has
- 8 protons
- 8 neutrons (16-8)
- 8 electrons (since we're talking about a neutral O atom)
Well the atomic number,
..........And for the neutral atom,