Atomic Radius
Trends in values of atomic radius
This is half the distance between the nuclei of two atoms of the same element held together by a single covalent bond.
Trends in value of atomic radii
Atomic radius increases down any group.
This is because (i) there is an increase in the number of electron shells as we move down a group and (II) there is a screening effect due to the inner electron shielding the outer electrons from the nuclear charge.
Atomic radius decreases across anyone period.
This is because (i) there is an increase in nuclear charge.
Ionisation energy
First ionisation energy: this is the minimum energy required to remove the most loosely bound electron from a gaseous atom in its ground state.
Ionisation energy decreases in moving down anyone group:
This is because there is (i)an increase in atomic radius and (ii) a screening effect by filled inner electron shells. ionisation energy generally increases in moving across a period this is due to (i) a decrease in atomic radius and (ii) an increase in nuclear charge.
Exception: nitrogen has a higher I.E than oxygen. If we examine the electronic configuration ;
Paulis exclusion principle : No more than 2 electrons can occupy an orbital and this they can do only if they have opposite spin
Hund’s rule of maximum multiplicity: When two or more orbitals of equal energy are available, the electrons fill them in singly before filling them in in pairs.
Electronic Configuration: 1sᶻ 2sᶻ 2p⁶ 3sᶻ 3p⁶ 4sᶻ 3d 4p⁶
This is half the distance between the nuclei of two atoms of the same element held together by a single covalent bond.
Trends in value of atomic radii
Atomic radius increases down any group.
This is because (i) there is an increase in the number of electron shells as we move down a group and (II) there is a screening effect due to the inner electron shielding the outer electrons from the nuclear charge.
Atomic radius decreases across anyone period.
This is because (i) there is an increase in nuclear charge.
Ionisation energy
First ionisation energy: this is the minimum energy required to remove the most loosely bound electron from a gaseous atom in its ground state.
Ionisation energy decreases in moving down anyone group:
This is because there is (i)an increase in atomic radius and (ii) a screening effect by filled inner electron shells. ionisation energy generally increases in moving across a period this is due to (i) a decrease in atomic radius and (ii) an increase in nuclear charge.
Exception: nitrogen has a higher I.E than oxygen. If we examine the electronic configuration ;
Paulis exclusion principle : No more than 2 electrons can occupy an orbital and this they can do only if they have opposite spin
Hund’s rule of maximum multiplicity: When two or more orbitals of equal energy are available, the electrons fill them in singly before filling them in in pairs.
Electronic Configuration: 1sᶻ 2sᶻ 2p⁶ 3sᶻ 3p⁶ 4sᶻ 3d 4p⁶