Post on 13-Nov-2014
description
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