Periodic table

in order of increasing atomic mass in columns
those with similar properties in rows
switched iodine and tellurium to better matched groups

left gaps so could see what group the missing would go in and predict its properties
filled in when discovered later

he had arranged them in order of relative atomic mass however isotopes of the same element have different atomic masses

amount of protons = atomic number

Elements are arranged in order of increasing atomic mass in rows called periods
Those with similar chemical properties are in the same vertical columns called groups

non metals= right of the 'staircase' need to gain electrons in order to gain the structure of a noble gas
metals= the rest

the number of occupied shells= the period number
electrons in the outer shell= the group number

maximum of 2 in the first shell
maximum of 8 in the outer shells