Periodic Table

Mendeleev did first attempt to arrange the elements in the table form according to physical and chemical properties but it failed due to many demerits- He provided the periodic Law

Periodic Law - it states that

“ The Properties of the elements are a periodic function of their atomic weight”

Mendeleev arranged elements in the groups and periods

• Groups - Vertical line in the table is known as group

• Period - Horizontal line in the table is known as period

In Mendeleev's periodic table he left gaps which was modified by Mosely.

MODERN PERIODIC TABLE:

Atomic Number - it is a fundamental property because it increases regularly from element to element and every element has fixed atomic number.

1913 Mosely discovered the modern periodic table - according to him atomic number is the basic property of an atom and elements should be arranged on the basis of atomic number not on basis of atomic mass. Atomic number is the number of electron in an atom and atomic number provide the electronic configuration in the periodic tale. Periodic table composed with 7 rows and 8 columns.

Periods in the Periodic Table

There are seven horizontal lines in periodic table known as periods. In periods physical and chemical properties changes from left to right. These periods are categorized as short periods and long periods

• First Period(shortest period)

1. This period contains only two elements Hydrogen (H) and Helium (He)

2. K-shell is filled in this period

• Second and Third Period(Short Period

1. Each periods contain eight elements.

2. In these Periods L and M shells are being filled by electron

3. Second period contains Li, Be, B, C, N, O,F and Ne.

4. Third period contains Na, Mg, Al, Si, P,S, Cl, and Ar

• Fourth and Fifth Period(Long Period)

1. Each period contain 18 elements

2. In these periods M and N shells are being filled by electrons

3. Fourth period starts from Potassium (K) and ends on Krypton (Kr)

4. Fifth period starts from Rubidium (Rb) and ends on Xenon (Xe).

• Sixth Period(Longest Period)

1. This period contains 32 elements

2. The 14 elements in the bottom are named as Lanthanides

3. Sixth periods starts from Cesium (Cs) and ends with Radon (Rn)

• Seventh Period (Incomplete Period

1. This period starts from Francium (Fr)

2. This period is consider as incomplete

3. This period contains a group of 14 elements known as Actinides

   Groups in Periodic table:

There are Eight vertical columns in periodic table known as groups. The sub groups are divided on the basis of their similar properties as A and B and placed together in periodic table

1. The elements of sub group A are called Main or Representative Elements

2. The elements of sub group B are called Transition Elements

There are following groups - lets discuss one by one

• Group I A (Alkali Metal) or Lithium Family -

1. This Group include Lithium (Li), Sodium (Na), Potassium (K), Rubidium (Rb), Cesium (Cs and Francium (Fr)

2. Contain one electron in outermost shell, very reactive and have low melting point.

• Group II A(Alkaline Earth Metals) or Beryllium Family

1. This includes beryllium (Be), magnesium (Mg), calcium (Ca), strontium (Sr), barium (Ba), and radium (Ra)

2. Contain two electron in outermost shell so can lose two electron

3. Irregular melting points and densities

• Group III A(Boron Family)

1. It includes boron (B), as well as the metals aluminum (Al), gallium (Ga), indium (In), and thallium (Tl)

2. have three electron in outermost shell and can lose three

• Group IV A(Carbon Family)

1. This Group include carbon (C),silicon (Si), Germanium (Ge), Tin (Sn) and Lead(Pb)

2. Have four electron in outermost shell

3. carbon is non-metal, Si and Ge is metalloid (having properties of both metal and non-metal) Pb is metal.

• Group V A(Nitrogen Family)

1. This Group include Nitrogen (N), Phosphorus (P),Arsenic (As), Antimony (Sb) and Bismuth (Bi)

2. Outermost shell contain 5 electrons

3. except nitrogen all exist in allotropic form

• Group VI A(Oxygen Family)

1. It includes the nonmetals oxygen (O), sulfur (S), and selenium (Se), the metalloid tellurium (Te), and the metal polonium (Po)

2. Contain 6 electron in outermost shell

• Group VII A(Halogen Family)

1. It includes halogens: fluorine (F), chlorine (Cl), bromine (Br), iodine (I), and astatine (At)

2. contain 7 electrons

3. all are non- metal except At

• Group VIII A( Inert or Nobel gases)

1. This Group include Helium(He), Neon(Ne), Argon(Ar), Krypton (Kr) Xenon(Xe) and Radon(Rn).

2. unreactive - outermost shell contains 8 electrons

• Group IB to VIII B( Transition Elements)

1. These Groups are metals

2. valence shell is incomplete