Periodic Table

Periodic Table is an arrangement of elements in the form of rows and column, that arranged in a way that elements shows a kind of decrease and increase in their properties like ionic radius, atomic radius, ionization potential etc. when we move right-left or up-down in a row or column. Columns are called as Groups and rows are called as Periods.

To easily remember and understand we have divided it into a number of blocks like s-,p-,d- and f-blocks.

• s-block elements are known as Alkali & Alkaline earth metals, they belongs to group (column) 1 & 2.
• p-block elements are known as Chalcogen, Picogens, Halogens and Inert gases. They belong to group 13-18.
• d-block elementsare known as Transition elements. They belongs to group 3-12.
• f-block elements known as Inner Transition elements. These are also called as rare earth metals.

The periodic table have two horizontal rows at the bottom, first (upper) one is Lanthanides elements and the lower one is Actinide elements. Both contains 14 elements

Periodic Properties :

1. Atomic radii : The distance from center of the nucleus to the outermost shell containing electrons called atomic radius. It is expressed in terms of covalent radii, metallic radii and van-der-wall radii. The size of these atomic radii are as follows.
   • van-der-wall radii > metallic radii > covalent radii
   • Atomic radii decreases from left to right in a period and increases in a group from up to down.
2. Ionic radii : The effective distance from center of nucleus to the ion which it exerts it’s influence on the electron cloud is called ionic radii.
   • The size of ionic radii are as – Anionic radii > atomic radii > Cationic radii
   • Ionic radii decreases from left to right in a period and increases from up to down in the group.
3. Ionization Potential : The amount of energy required to remove an electron from isolated gaseous atom is called Ionization Potential (IP) or Ionization Energy (IE)
   • A(g) – e^– + required energy = A⁺ (g)
   • Ionization potential increases from left to right in a period and decreases from up to the down in the group.
   • unit = KJ /mol or eV/atom
4. Electron affinity (E_a) : The energy released during addition of an extra electron in isolated gaseous atom is called electron affinity.
   • A(g) + e^– = A^– (g) + released energy
   • Cl (chlorine ) has the highest electron affinity. It’s unit is KJ/ mol or eV/atom.
   • Electron affinity increases from left to right in a period and decrease from top to down in a group.
5. Electronegativity (E_n): The relative electron attracting tendency of an atom for a shared pair of electrons in a chemical bond is called electronegativity. It has no unit.
   • Florine (F) is the most electronegative atom and Cesium (Cs) is the least electronegative element.
   • E_n = (IP + E_a)/5.6
   • For ionic compounds E_n >1.7
   • For polar co-valent compounds E_n <1.7
   • For non-polar co-valent compounds E_n =0
   • Electronegativity increases from left to right in the period and decreases from the top to the bottom in the group.
   • Diagonal relationship (Be-Al) (B-Si)
6. Lattice Energy : The amount of energy released during formation of one mole of ionic compound from its constituents ions is called Lattice energy.
7. Hydration Energy : The amount of energy released during dissolution of one mole of compound into water, is called hydration energy.

• If Hydration energy > Lattice energy, compound is soluble in water.
• If Hydration energy < Lattice energy, compound is insluble in water.