History of Periodic Table

History of Periodic Table. Deekshit.V VII -B.

The periodic table - tabular array of the organized chemical elements.

Representation in Periodic table. Atomic number The number of protons in the nucleus of the atom. Atomic mass The average mass of the atoms in an element. CARBON 6 12.01 Element name Usually from a Greek or Latin word for the element or a substance containing the element. Symbol Short-hand abbreviation for the element name..

Evolution of Periodic table. John Dalton Suggested arranging the element according to their atomic number –lightest to heaviest. Johann Dobereine r Arranged elements with similar properties to similar group He made link between atomic number and masses and classified element in triads. the properties of the middle element could be predicted from the properties of the other two. John Newland He noticed that there were similarities between elements with atomic weights that differed by seven. He called this The Law of Octaves, drawing a comparison with the octaves of music. Dmitri Mendeleev organised the elements in February of 1869. arranged the elements in the periodic table in order of increasing atomic mass.

How do atomic structures (electron arrangement) change in a period with increase in atomic numbers, moving left to right?.

Types of Element arrangement. Elements are classified on their properties as Metals Non metals Metalloids Another classification is based on groups Alkali metals (Group 1) Alkaline earth metals(Group 2) Halogens(Group 7) Noble gases (Group 0)..

Alkali metals (Group 1). Metals are not alkalis but oxides and hydroxide form that are alkaline in nature. Has only one electron in the outermost shell. Very reactive metals ..

Alkali metals (Group 1). Physical Properties. Soft and easy to cut. Shiny when cut but tarnish in the air. Down the group density of the metal increases. Down the group, melting point decreases. Down the group ,boiling point decreases..

Alkaline earth metals(Group 2). Metals that make oxides that are alkaline. Group 2 element has 2 electron in the outershell ..

Alkaline earth metals(Group 2). Physical Properties.

Vol. III - Semiconductors - Solid-State Device Theory - Valence and Crystal Structure.

Halogens(Group 7 ). Physical Properties. Very reactive and forms salt Color gets darker has we go down the group. Boiling point increases down the group..

Noble Gases /Inert Gases(Group 0). Very unreactive Non-metals. 8 valence electron in outer shell..

Inert Gases/Nobel Gases(Group 0 ). Physical Properties.

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