Question

Give the expected ground-state electron configurations for the following elements:

a) Ti

b) Ru

c) Sn

d) Sr

e) Se

Please explain this process as well, thank you!

Answer 1

Ground state electron configuration is the electron configuration (arrangement within an atom) at the lowest energy level possible.

1)Electrons are filled in various orbitals within an atom according to Aufbau's principle.This principle states that electrons occupy the lowest energy orbitals first,before occupying the higher energy orbitals.

2) second principle to be followed is Pauli's exclusion principle-A maximum of two electrons with opposite spin can occupy an orbital

3) Hund's rule of maximum multiplicity states that a greater total spin state makes the resulting atom more stable.

Accordingly, it can understood that if there are two or more orbitals of equal energy, electrons will occupy them singly first and then fill them up again in another round to make pairs of electrons..

The orbitals s,p,d,f have their own capacity of intaking electrons, and so they are filled accordingly.

s orbital can take a miximum of 2 electrons

p orbitals have three sub-levels, say, px,py and pz and each sub- orbital can occupy 2 electrons each.A total of 6 electrons for p orbitals.

d orbitals have 5 sub-levels ,dxz.dxy,dyz,dz2,dx2-y2.Each sub-orbital can take two electrons.So a total of 10 electrons can be accomodated.

f orbitals have 7 sub -levels ,Each sub-orbital can take two electrons.So a total of 10 electrons can be accomodated.

Now , the orbitals are arranged in order of their increasing energy as follows=

1s,2s,2p,3s,3p,4s,3d,4p,5s,4d...... here number 1,2,3 ...represents various energy levels or shells in an atom.Each level has sub-levels called orbital.example 2p belongs to level 2 or n=2

The order can be easily found out from the diagonal rule using an spdf chart.

Now lets find out the expected ground state electron configuration for the given elements.

1)Ti(titanium) atomic number from periodic table=21

no of electrons =22

Electronic configuration=1s2 2s2 2p6 3s2 3p6 4s2 3d2

[Ar] 4s2 3d2

2)Ru (atomic number 44)

E.c=1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p6 5s2 4d6

becomes 1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p6 5s1 4d7 (hund's rule) or

[kr] 5s1 4d7

3) Sn(50) no of electons=atomic no=50

1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p6 5s2 4d10 5p2

or [kr] 5s2 4d10 5p2

4) Sr (38) no of electons=atomic no=38

1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p6 5s2

or [Kr] 5s2

5)Se(34)

1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p4

or [Ar] 4s2 3d10 4p4