Here students can locate TS Inter 1st Year Chemistry Notes 2nd Lesson Classification of Elements and Periodicity in Properties to prepare for their exam.
TS Inter 1st Year Chemistry Notes 2nd Lesson Classification of Elements and Periodicity in Properties
→ According to Modern periodic law, the physical and chemical properties of ele-ments are periodic functions of their atomic numbers (or) electronic configurations.
→ In the Long form of the periodic table the elements are arranged in the increasing order of their atomic numbers.
→ There are seven horizontal rows (periods) and eighteen vertical columns (groups) in the long form of periodic table.
→ Based on the entering of differentiating electron, elements are classified into four blocks. They are s – block, p – block, d – block and f – block.
→ Based on the number of incompletely filled shells, elements are classified into four types. They are :
- Inert gas elements
- Representative elements
- Transition elements
- Inner transition elements.
→ Repetition of properties of elements (i.e., similar elements) after definite regular intervals is called periodicity. The cause of periodicity is due to similar outer electronic configuration.
→ The distance between the nucleus and outermost electron of an atom is called atomic radius.
→ The regular decrease in the size of lanthanides from left to right, due to the ineffective shielding offered by inner f – orbital is called Lanthanide contraction.
→ The decrease in the attractive force of the nucleus on the valence electrons by the electrons of inner shells is called screen-ing effect or shielding effect.
→ The minimum amount of energy required to remove an electron present in the out-ermost orbit of a neutral isolated gaseous atom is called ionisation potential.
→ The amount of energy released when an electron is added to a neutral, isolated gaseous atom is called electron affinity.
→ The tendency of an atom to attract shared pair of electrons towards itself in a cova-lent molecule is called Electronegativity.
→ According to Mullikan scale, the E.N. value of an element is an average of its IP and E.N.
→ According to Pauling scale the difference in the E.N. values is given by
XA – XB = 0.208 √Δ.
→ The combining capacity of an atom with other atoms is called valency. It is the number of H atoms or the number of Cl atoms or double the number of ‘O’ atoms with which one atom of the element combines.
→ The tendency of losing electrons is called Electropositivity.
→ Metallic oxides are basic and non-metallic oxides are acidic.
→ The reluctance of ns2 electrons to get un-paired and take part in bonding is called inert pair effect’.
→ The first element of a group shows some similarities with the second element of the next higher group. This is called diagonal relationship’.