Chemistry

Periodic Table

Periodic Table

The table which classifies the elements in such a way that elements having similar properties our group together.

Historical Development of the Periodic Table

Dobereiners Triads

3 element group together in such a way that the atomic weight of the central element is their average of the atomic weight of the other two.

Newlands Law of Octaves

Elements arranged in increasing order of atomic weight as the first and eighth elements show similar properties.

Mendeleev Periodic Table

The physical and chemical properties of elements are the Periodic functions of their atomic weight.

The elements are arranged in increasing atomic masses in the form of horizontal and vertical columns called respectively; there were 8 groups and 7 periods in the periodic table

Defect
  • He was not able to justify the place of isotopes.
  • Element with high atomic masses was placed before the elements with atomic mass.
  • No place for inert gases.

Modern Periodic Law

Moseley proposed modern periodic law. the physical and chemical properties of an element are periodic functions of their atomic number.

Modified Mendeleev Periodic Table

  • In this table, there are 9 groups and 7 periods.
  • Accept 8 and 0 groups all the groups divided into two subgroups A and B.
  • The element of subgroup A was placed on the right side.
  • Lanthanides and Actinides are placed at the bottom of the periodic table.
Defects
  • of hydrogen.
  • Highly reactive alkali metals please with less reactive metals.
  • Elements with similar properties placed in different groups.
  • of Lanthanides and Actinides.

Long-form of Periodic Table

The table is divided into 18 vertical columns called groups and 7 horizontal rows called periods. This periodic table is divided into 4 blocks.

  • s- block (group 1-2)
  • p- block (group 13-18)
  • d- block (group 3-12)
  • f- block (at the bottom)
Periodic Table

Description of s,p,d,f Block Elements

s-block elements

It includes alkali metals and alkaline earth metals.

General characteristics
  • Soft metals
  • Low melting and boiling points.
  • Highly reactive.
  • Highly electropositive show + 1 and + 2 oxidation state.

p- block elements

also called post-transition elements groups 16 and 17 are also called chalcogens and halogens respectively And group 18 elements are called noble gases.

General characteristics
  • Contain metal, metalloids, and non-metals.
  • Show variable oxidation states.
  • Elements form ionic compounds and some elements can form both ionic and covalent bonds.
  • Most of the elements form acidic oxides.
  • Noble gases are chemically unreactive.

d- block elements

Also called transition elements.

General characteristics
  • Hard solids.
  • Having a high melting and boiling point.
  • Good conductor of heat and electricity.
  • Form colored ions and colored compounds.
  • Form alloy.

f- block elements

  • Also called inner transition elements.

4f series – Lanthanides

5f series – Actinides

  • All our metals with high melting and boiling point.
  • Show a variable oxidation state.
  • Forms colored and coordination compounds.

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