Question

Describe the periodic table periodic properties and variations of properties

Answer 1

The periodic table arranges the elements by periodic properties, which are recurring trends in physical and chemical characteristics. ... These trends explain the periodicity observed in the elemental properties of atomic radius, ionization energy, electron affinity, and electronegativity.Major periodic trends include: electronegativity, ionization energy, electron affinity, atomic radius, metallic character, ionic radius and reactivity. Periodic trendsarise from the arrangement of elements in the periodic table and allow chemists to quickly and reliably predict an element's properties.

Answer 2

• PERIODIC PROPERTIES : The properties which appear at regular intervals in the periodic table are called periodic properties and the phenomenon is called periodicity in properties of elements. In more clear words, we can say, the phenomenon in which repetition of similar properties of elements occurs or reappears at atomic number intervals of 2,8,8,18,18 ,32 is called periodicity and these properties are called periodic properties. Several periodic properties are - Atomic radii, Ionisation potential, Electron affinity, Electronegativity, Non-metallic and metallic character, Melting and Boiling point, etc.

• DEFINITIONS : (i) ATOMIC RADIUS is the distance between the centre of the nucleus and the outermost shell of an atom.

(ii) IONISATION POTENTIAL is the amount of energy required to remove an electron from the outermost shell of an isolated gaseous atom.

(iii) ELECTRON AFFINITY is the amount of energy released when an atom in the gaseous state accepts an electron to form an anion.

(iv) ELECTRONEGATIVITY : It is the tendency of an atom to attract electrons towards itself when combined in a compound.

(v) METALLIC AND NON METALLIC CHARACTER : In terms of electron loss or gain, an element is said to be a non metall if it gains one or more electrons and a metal if it loses one or more electrons.

(vi) MELTING AND BOILING POINTS : These are the fixed temperatures at which several elements of the periodic table melts (converts from solid to liquid) or freezes (converts from liquid to solid) respectively.

• VARIATION : (i) On moving from left to right across a period in the periodic table, Atomic size, Metallic character of an element decreases whereas Ionisation potential, Electron affinity, Electronegativity, Non metallic character of an element increases.

(ii) On moving down a group in the periodic table, Atomic size, Metallic character of an element increases whereas Ionisation potential, Electron affinity, Electronegativity, Non metallic character of an element decreases.

• FACTORS ON WHICH SEVERAL PERIODIC PROPERTIES DEPENDS : (i) Periodic properties like Atomic size of an element depends on the number of shells and nuclear charge of that element. Other properties like Ionisation potential, Electron affinity, Electronegativity depends on the atomic size and nuclear charge.

(ii) Metallic or non-metallic character of an element depends upon two factors, namely, ATOMIC RADIUS and IONISATION POTENTIAL. When atomic radius of an element increases, then metallic character increases and non-metallic character decreases. When ionisation potential increases, then metallic character decreases and non-metallic character increases.