QUANTUM NUMBERSCAPE Unit 1

SCHROEGINDER WAVE EQUATION Wave-particle duality of electrons

The position of an electron is described in terms of probability density

Orbital region (volume of space around the nucleus)

where there is a high probability of finding an electron of a given energy

Atomic model 3-D 3 quantum numbers (principal, angular,

magnetic)

QUANTUM NUMBERS

Describe the size, shape and orientation in space of the orbitals

Principal Quantum Number (n) Energy level of the electron Maximum number of electrons at n level is 2n2

Energy Level No. of electrons

n = 1 2

n = 2 8

n = 3 18

n = 4 32

QUANTUM NUMBERS

Angular Quantum Number (l) Sublevels in n & Shape of the orbitals s, p, d, f Each energy level has n sublevels

Energy Level No. of Sublevels

Sublevels

n = 1 1 1s

n = 2 2 2s, 2p

n = 3 3 3s, 3p, 3d

n = 4 4 4s, 4p, 4d, 4f

QUANTUM NUMBERS

Magnetic Quantum Number Number of orbitals within a sublevel

Sublevel No. of Orbitals

Max. Electrons

s 1 2

p 3 6

d 5 10

f 7 14

QUANTUM NUMBERS

Fourth Quantum Number????????

Spin Quantum Number Each electron has a magnetic field and a spin

associated with that electron

Pauli Exclusion Principle No more than two (2) electrons can occupy an

orbital Two (2) electrons in the same orbital must have

opposite spins NO TWO ELECTRONS IN AN ATOM HAVE THE

SAME FOUR QUANTUM NUMBERS

SHAPES OF ORBITALSCAPE Unit 1

Dr. Z. Clarke

SHAPES OF ORBITALS

s orbital Each energy level has one s orbital Maximum number of electrons = 2 Spherical

1s and 2s orbitals are similar in shape however electron density is closer to the nucleus for the 1s orbital

SHAPES OF ORBITALS

p orbitals Each energy level has three (3) degenerate p

orbitals i.e. 3 orbitals of EQUAL ENERGY

Dumb-bell shape

ELECTRONIC CONFIGURATIONCAPE Unit 1

Dr. Z. Clarke

ELECTRONIC CONFIGURATIONS

s orbitals have slightly lower energy than the p orbitals at the same energy level i.e. 2s < 2p

s orbital will ALWAYS fill before corresponding p orbitals

s orbital have the lowest energy then p, d, f s < p < d < f

ELECTRONIC CONFIGURATIONS

Anomaly Irregularity in the position of the 3d and 4s

orbitals 3d has slightly more energy than 4s 4s fills first then 3d orbitals followed by 4p

orbitals

ELECTRONIC CONFIGURATIONS Describes the arrangement of electrons in the

orbitals of an atom

How are electronic configurations worked out?

Electrons are added one at a time, starting with the lowest energy orbital (Aufbau Principle)

No more than two electrons can occupy an orbital (Pauli Exclusion Principle)

Electrons fill degenerate orbitals one at a time with parallel spin before a second electron is added with opposite spin (Hund’s Rule)

ELECTRONIC CONFIGURATIONS

How do we write electronic configurations?

Principal Quantum number (1, 2, 3 etc) Symbol for the orbital (s, p, d, f) Superscript that shows the number of electrons

in the sublevel number of electrons

in orbital

energy level 1s2

type of orbital

ELECTRONIC CONFIGURATIONS

Atomic Number Symbol Electronic Configuration

1 H 1s1

2 He 1s2 or [He]

3 Li [He] 2s1

4 Be [He] 2s2

5 B [He] 2s2 2p1

6 C [He] 2s2 2p2

7 N [He] 2s2 2p3

8 O [He] 2s2 2p4

9 F [He] 2s2 2p5

10 Ne [He] 2s2 2p6 or [Ne]

ELECTRONIC CONFIGURATIONS

Atomic Number Symbol Electronic Configuration

11 Na [Ne] 3s1

12 Mg [Ne] 3s2

13 Al [Ne] 3s2 3p1

14 Si [Ne] 3s2 3p2

15 P [Ne] 3s2 3p3

16 S [Ne] 3s2 3p4

17 Cl [Ne] 3s2 3p5

18 Ar [Ne] 3s2 3p6 or [Ar]

19 K [Ar] 4s1

20 Ca [Ar] 4s2

ELECTRONIC CONFIGURATIONS

Atomic Number Symbol Electronic Configuration

21 Sc [Ar] 4s2 3d1

22 Ti [Ar] 4s2 3d2

23 V [Ar] 4s2 3d3

24 Cr [Ar] 4s1 3d5

25 Mn [Ar] 4s2 3d5

26 Fe [Ar] 4s2 3d6

27 Co [Ar] 4s2 3d7

28 Ni [Ar] 4s2 3d8

29 Cu [Ar] 4s1 3d10

30 Zn [Ar] 4s2 3d10

ELECTRONIC CONFIGURATIONS – ABBREVIATED

He, Ne and Ar have electronic configurations with filled shells of orbitals Abbreviated electronic configurations

He = 1s2 or [He]

Ne = 1s2 2s2 2p6 or [Ne]

Ar = 1s2 2s2 2p6 3s2 3p6 or [Ar]

ELECTRONIC CONFIGURATIONS - SPECIAL

After 3p orbitals are filled, 4s orbital is filled before the 3d orbital

4s orbital is at a slightly lower energy than the 3d

K is [Ar] 4s1

Ca is [Ar] 4s2

Sc is [Ar] 4s2 3d1

ELECTRONIC CONFIGURATIONS - SPECIAL

After Sc, the 3d orbitals are filled

Irregularity is seen in the electronic configuration of Cr and Cu

Cr is [Ar] 4s1 3d5

Cu is [Ar] 4s1 3d10

ELECTRONIC CONFIGURATIONS - SPECIAL

One electron has been transferred from the 4s orbital to the 3d orbital

Half-filled and filled sublevels of 3d orbitals decreases

Energy

Spin pairing of the 4s orbital increases

Energy

IONIZATION ENERGYCAPE Unit 1

Dr. Z. Clarke

IONIZATION ENERGY

1st Ionization Energy of an element Energy needed to convert 1 mole of its gaseous

atoms into gaseous ions with a single positive charge

M(g) M+(g) + e-

Energy required to remove each successive electron is called the 2nd, 3rd, 4th, etc. ionization energy

Ionization energies are positive because it requires energy to remove an electron

IONIZATION ENERGY – INFLUENCING FACTORS

Magnitude of ionization energy how strongly the electron to be lost is attracted

to the nucleus

Factors that influence ionization energy

Atomic Radii

Nuclear Charge

Shielding (Screening)

IONIZATION ENERGY – ATOMIC RADII

Atomic Radii

Distance of the outer electron is from the nucleus

As distance increases ( ), nuclear attraction for the outer electron decreases ( ), ionization energy decreases( )

IONIZATION ENERGY – ATOMIC RADII

Successive Ionization Energies of Sodium (Na)

Ionization Energy

Energy Orbital Electron Lost From

1st 496 3s

2nd 4562 2p

3rd 6912 2p

4th 9543 2p

5th 13353 2p

6th 16610 2p

7th 20114 2p

IONIZATION ENERGY – NUCLEAR CHARGE

Nuclear Charge

As nuclear charge increases, attraction of the nucleus for the outer electron increases, ionization energy increases

Atomic Radii and Electron Shielding (Screening) can outweigh the effect of nuclear charge

Cs has a larger nuclear charge than Na, loses electron more readily than Na

IONIZATION ENERGY – SHIELDING (SCREENING)

Screening Effect of Inner Electrons

Electrons experience repulsion by other electrons

Outer electrons are shielded from the attraction of the nucleus by repelling effect of inner electrons

Screening effect of electrons in lower energy levels is more effective than electrons in higher energy levels

IONIZATION ENERGY – SHIELDING (SCREENING)

Screening Effect of Inner Electrons

Electrons in same energy level has negligible screening effect on each other

As screening effect becomes more effective, ionization energy decreases