atomic structure and the perodic table- Edexcel AL full summary

Topic 2- atomic structure and the periodic table


Relative mass Relative charge
Proton 1 +1
Neutron 1 0
Electron 1/1840 -1


 Electron exist in energy levels surrounding the nucleus known as
quantum shells.
 The atomic number represents the number of protons in the nuclei
of an atom, which is also equal to the number of electrons in an
atom. (atomic number= number of protons= number of electrons)
 As the number of positive charges (protons) is equal to the number
of negative charges (electrons), an atom is said to be neutral.
 The mass number represents the total number of protons and
neutrons present in the nuclei of an atom. (mass number= number
of protons+ neutrons)
 Isotopes are atoms of the same element with the same atomic
number but different mass number. In other words, they have the
same number of protons but different number of neutrons.
 Isotopes have similar chemical properties due to identical electronic
configurations, but different physical properties due to different
masses.
 the relative isotopic mass of an element can be calculated using the
following formulae:




 a mass spectrometer measures the masses of atoms or molecules
and calculates the relative abundance of each positive ion and
displays this as a percentage.