Periodic Periodic TableTable

• Periodic tables reflects the electronic structures Periodic tables reflects the electronic structures

of the atom based on classification to different of the atom based on classification to different block (s,p,d,f)block (s,p,d,f)

• can deduce the configuration of any atom if we can deduce the configuration of any atom if we know :know :

Number of valence electronNumber of valence electron Period numberPeriod number Group no.- corresponds to the no. of valence Group no.- corresponds to the no. of valence

electron in an atomelectron in an atom

Electronic Configuration

OrbitalOrbital subshell s= only one type of orbital and found in all subshell s= only one type of orbital and found in all shells, starts from orbital (n=1)shells, starts from orbital (n=1)

Subshell p= 3 types of orbital; pSubshell p= 3 types of orbital; pxx,p,pyy,p,pzz. Found in all . Found in all shells except the 1shells except the 1stst shell, starts from n=2 shell, starts from n=2

Subshell d= 5 types of orbital, found in all shellSubshell d= 5 types of orbital, found in all shell except the 1except the 1stst and 2 and 2ndnd shell. starts from n=3. shell. starts from n=3.

Subshell f= 7 types of orbital and found in all shells Subshell f= 7 types of orbital and found in all shells except the 1except the 1stst, 2, 2ndnd and 3 and 3rdrd Shell. Starts from n=4. Shell. Starts from n=4.

OrbitalOrbital The s-Orbital (spherical shape)The s-Orbital (spherical shape)

The p-Orbital (pThe p-Orbital (pxx, p, pyy, p, pzz))

OrbitalOrbital Individual s-orbital & p-orbitalIndividual s-orbital & p-orbital

1s 2s 3s

px

py

pz

OrbitalOrbital

Collective s-orbital & p-orbitalCollective s-orbital & p-orbitaly

x

z

1s

2s

3s

y

y

z

Rules in Filling orbital with ElectronRules in Filling orbital with Electron

The Pauli Exclusion Principle states The Pauli Exclusion Principle states that each orbital can house a that each orbital can house a maximum of two electrons of maximum of two electrons of opposite spins.opposite spins.

If only one electron is houses in If only one electron is houses in orbital, it should be as:orbital, it should be as:If two electron are housed in a orbital, it should be indicated as:

Rules in Filling orbital with ElectronRules in Filling orbital with Electron

The Hund’s rule state that for a given set of The Hund’s rule state that for a given set of orbital with identical energy levels, the electron orbital with identical energy levels, the electron will occupy each orbital unpaired according to the will occupy each orbital unpaired according to the number of available electrons to give a set of half number of available electrons to give a set of half filled orbital with the same spin or parallel spin, filled orbital with the same spin or parallel spin, before pairing of electrons with opposite spin before pairing of electrons with opposite spin takes place.takes place.

This is because with such arrangement the This is because with such arrangement the electrons are at maximum distance of separation electrons are at maximum distance of separation and the repulsive force between the electrons are and the repulsive force between the electrons are minimum. Hence a higher stability of electronic minimum. Hence a higher stability of electronic configuration achieved.configuration achieved.

Steps filling p-orbital according to Steps filling p-orbital according to Hund’s RuleHund’s Rule

i.i. iiii iii.iii.

And not

Predicting the Electronic Configuration of Predicting the Electronic Configuration of Atoms and Ions Based on the Proton Atoms and Ions Based on the Proton

NumberNumber

Electronic Configuration :Electronic Configuration : Na= 2.8.1 ; Na= 2.8.1 ; NaNa++ = 2.8 = 2.8

Electronic Orbital:Electronic Orbital: Na= 1sNa= 1s22,2s,2s22,2p,2p66,3s,3s11

NaNa++ = 1s = 1s22,2s,2s22,2p,2p66

Neon gas: 1sNeon gas: 1s22, 2s, 2s22, 2p, 2p66

Aluminium: 1sAluminium: 1s22, 2s, 2s22, 2p, 2p6, 6, 3s3s22, 3p, 3p1 1 (This (This can be simplified as [Ne] 3scan be simplified as [Ne] 3s22, 3p, 3p11

Argon: 1sArgon: 1s22, 2s, 2s22, 2p, 2p6, 6, 3s3s22, 3p, 3p6 6

Potassium : 1sPotassium : 1s22, 2s, 2s22, 2p, 2p6, 6, 3s3s22, 3p, 3p66,4s,4s1 1

(This can be simplified as [Ar] 4s(This can be simplified as [Ar] 4s11

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