Quantum Theory

Question 1

What did Niels Bohr predict?

Answer 1

electrons exist in orbits with specific energy

Question 2

What does atomic emission spectra provide evidence f?

Answer 2

subshells within each energy level

Question 3

What does classical theory assume electrons exist as?

Answer 3

a particle (with mass and charge)

Question 4

What does experimental evidence show that electrons can have?

Answer 4

wave-like properties (show diffraction and interference)

Question 5

What does the wave-like nature of electrons make it impossible to do? What is this known as?

Answer 5

specify exactly the position and momentum of the electron - Heisenburg Uncertainty Principle

Question 6

How can the discrete lines seen in the emission spectra be explained?

Answer 6

if the electron is regarded as having the properties of both particles and waves

Question 7

What does quantum theory suggest? (3)

Answer 7

Electrons within atoms behave as waves of different shapes and sizes

The waves are known as orbitals

Each orbital can hold a maximum of two electrons

Question 8

What are orbitals defined by?

Answer 8

Quantum numbers

Question 9

What is an orbital?

Answer 9

a region of space where the probability of finding the electron is >95% (i.e. there is uncertainty)

Question 10

What are the shapes of orbitals?

Answer 10

S
P
D

Question 11

What are S orbitals said to be?

Answer 11

spherically symmetrical

Question 12

How many types of S orbitals are there?

Answer 12

1

Question 13

What is the maximum number of electrons S orbitals hold?

Answer 13

2

Question 14

What is the maximum number of electrons P orbitals hold?

Answer 14

6

Question 15

What are the 3 types of P orbitals?

Answer 15

Px
Py
Pz

Question 16

What are the 3 P orbitals described to be?

Answer 16

degenerate, i.e. have the same energy

Question 17

What is the maximum number of electrons D orbitals hold?

Answer 17

10

Question 18

What are the 5 types of D orbitals?

Answer 18

dxy
dxz
dyz
dx2-y2
dz2

Question 19

What are the 5 D orbitals described to be?

Answer 19

degenerate, i.e. have the same energy

Question 20

Describe the principal quantum number

Answer 20

n
Tells us the main energy level
n has values from 1 to infinity
first shell n=1

Question 21

Describe the angular momentum quantum number

Answer 21

This describes the shape of the orbital and tells us which subshells are present in the principal shell
l=0 - S
l=1 - p
l=2 - d

Question 22

Describe the magnetic quantum number

Answer 22

Gives u the number of each type of orbital
m has values from -l to +l
l= 0 = one S orbital
l=1 = -1,0,1 = 3 p orbitals

Question 23

What do electrons appear to do?

Answer 23

spin on their axis

Question 24

What do spinning charges create?

Answer 24

a magnetic field

Question 25

Describe the spin quantum number

Answer 25

gives the direction of electron spin and has values of s= +1/2 or -1/2

Question 26

What must each electron in the same orbital have?

Answer 26

opposite spins

Question 27

How can electron arrangements be determined?

Answer 27

by placing electrons in 'boxes', where each box represents an atomic orbital

Question 28

What are the 3 principles must be considered when determining the order of filling of orbitals?

Answer 28

1. Aufbau principle 2. Hund's Rule 3. Pauli's Exclusion Principle

Question 29

What is Aufbau principle?

Answer 29

Electrons occupy the lowest energy level available i.e. those closest to the nucleus

Question 30

What is Hund's Rule?

Answer 30

Electrons occupy degenerate orbitals singly before any orbital gets a second electron

Question 31

What is Pauli's Exclusion Principle?

Answer 31

the maximum number of electrons in any atomic orbital is two and if there are two electrons in an orbital they must have opposite spins

Question 32

What is the order of filling orbitals?

Answer 32

1s 2s 2p 3s 3p 4s 3d 4p

Question 33

What does shortened electronic configuration use?

Answer 33

the notation of the preceding noble gas in place of filled inner shells

Question 34

What are the chemical properties of an element dictated by?

Answer 34

the electrons in the outer shell

Question 35

The periodic table is divided into blocks depending on what?

Answer 35

the type of orbital which holds the outer electrons

Question 36

What is the first ionisation energy?

Answer 36

the energy required to remove one mole of electrons from one mole of gaseous atoms

Question 37

What two factors affect I.E?

Answer 37

atomic radius and nucleur charge

Question 38

Describe I.E for across a period

Answer 38

nucleur charge increases/ same number of shells

Question 39

Describe I.E for down a group

Answer 39

increasing atomic radius

Question 40

Across period 2 what are the 2 anomalies?

Answer 40

1st I.E. shows a dip from - . Be to B (group 2 to group 3) - N to O (group 5 to group 6)

Question 41

How can the variations in ionisation energies can be explained?

Answer 41

in terms of the relative stabilities of the electronic configuratons of the element

Question 42

Explain the anomalies in I.E. for group 2 to group 3 (Be to B)?

Answer 42

In Be, the electron is removed from the 2s orbital, which is a FULL sub-shell. This is a STABLE ARRANGEMENT, therefore more energy is required to remove the electron. In B, the electron is removed from a 2p orbital which is further from the nucleus, therefore electron requires less energy to be removed

Question 43

Explain the anomalies in I.E. for group 5 to group 6 (N to O)?

Answer 43

In N, all p orbitals are HALF-FILLED. This is a relatively STABLE ARRANGEMENT, therefore more energy is required to remove an electron In O, there are 2 paired electrons in one of the 2p orbitals. Repulsion between the paired electrons makes the electron easier to remove. Also, the stable half-filled arrangement is lost.