4.1 development of the periodic table of elements

antoine lavoisier

• first list, contained 33 elements (4 groups)

• classified elements according to certain groups such as gases, non-metals, metals and metal oxides

• not accurate because he also classified light, heat and a few other compounds into the groups as elements

johann w dobereiner

• he classified three elements of the same nature into a group known as triads.

  • lithium, sodium and potassium → triad

  • chlorine, bromine and iodine → triad

• he proposed that…

  • the relative atomic mass for the 2nd element in a triad is the average of the relative atomic mass of the 1st and 3rd elements of the triad

• his classification, though limited to a few elements, showed the relationship between the chemical properties of elements and atomic mass.

john newlands

• he compiled elements known at that time in order of increasing atomic masses

• law of octaves

  • the same chemical and physical properties were repeated at every eighth element

  • this recurrence in properties of the eight element showed the presence of a periodic pattern in the properties of elements

lothar meyer

found that elements with similar chemical properties occupy a corresponding position on a curve of graph of the volume of atom versus the relative atomic mass of the element which he plotted.

• he suggested that there is a periodic relationship of elements based on the relative atomic masses

• also proved the recurrence in properties of elements similar to newlands

dmitri mendeleev

he arranged elements to the order of increasing atomic masses. the elements with similar chemical properties are grouped together (same vertical columns)

• he left empty spaces for the elements which have yet to be discovered at the time

• successfully predicted the properties of unknown chemicals at that time

henry moseley

studied the frequencies of X-ray released by various elements and found a relationship between the X-ray spectrum and proton numbers of an element.

• modernised the mendeleev periodic table by updating and re-arranging the elements in order of increasing proton numbers (atomic numbers) horizontally

• elements with the same chemical properties were arranged into the same groups

in the periodic table of elements, the elements are arranged in…

ascending order of proton numbers horizontally, ranging from 1 to 118. elements with similar chemical properties are placed in the same vertical columns.

new elements which have been discovered recently …

• Nh, nihonium (113)

• Mc, moscovium (115)

• Ts, tennessine (117)

• Og, oganesson (118)