UNIT 1) 3) Atomic Orbitals and Electron Configuration

Question 1

How can the discrete lines in atomic spectra be explained

Answer 1

The discrete lines observed in atomic spectra can be explained if electrons, like photons, also display the properties of both particles and waves.

Question 2

Within the atom how do electrons behave

Answer 2

Within the atom , electrons behave as standing (stationary )waves. These are waves that vibrate in time but do not move in space

Question 3

Different shapes and sizes of these “standing” waves are possible around the nucleus
What are these shapes and sizes known as ?

Answer 3

Different shapes and sizes of these standing waves are possible around the nucleus. These are known as orbitals

Question 4

Explain what an orbital is

Answer 4

• it is not possible to define a space in time where an electron is found - they are constantly moving
• however the probability of finding an electron within a certain volume of space can be calculated
• : the regions where there is a high probability of finding an electron are called atomic orbitals
  Therefore an orbital provides a defined volume of space where there is a high probability of finding an electron

Question 5

Probability of being able to find an electron in an atomic orbital

Answer 5

In atomic orbitals - there is approximately 90% chance of detecting an electron

Question 6

How many electrons can a single orbital hold (irrespective to size and shape)

Answer 6

2

Question 7

Electrons within atoms are said to be _________

- what does this mean

Answer 7

Electrons within atoms are said to be quantised

• this means that they can only posses fixed amounts of energy known as quanta
• as a result electrons can be defined in terms of quantum numbers

Question 8

What does quantum theory state

Answer 8

Quantum theory states that matter can only emit or absorb energy in small fixed amounts

Question 9

When an electron in an atom _______ a photon of energy it moves from a lower energy level to a higher energy level. When the electron drops back down energy is _______

Answer 9

When an electron in an atom absorbs a photon of energy it moves from a lower energy level to a higher energy level. When the electron drops back down energy is emitted.

Question 10

Rings are drawn around the nucleus of the atom to represent energy levels.

• The further away the rings are from the nucleus the ________ the energy
• as energy increases the levels become _______ together until they ________

Answer 10

• The further away the rings are from the nucleus the higher the energy
• as energy increases the levels become closer together until they converge

Question 11

What is the convergence point

Answer 11

An electron that has enough energy to take it beyond the convergence point has left the atom - this means it has been ionised

Question 12

Electrons are found in orbitals which are found in sub shells of energy level shells.
Each electron has an “address” how is this defined?

Answer 12

It is defined by a set of 4 quantum numbers

• 1st quantum number /principal quantum number
• 2nd quantum number / angular momentum quantum number
• 3rd quantum number / magnetic quantum number
• 4th quantum number / spin quantum number

Question 13

1st principle quantum number

• what does this refer to
• what is the symbol

Answer 13

• this refers to the energy shell where the electron is located : refers to the size and energy of the shell
• symbol n
  N=1 n=2 n=3 etc

Question 14

What happens to the size of orbital as value n increases

Answer 14

As value of n increases the size of the orbital also increases

Question 15

2nd quantum number - angular momentum

• what does this refer to
• symbol

Answer 15

• this is the type of sub shell within the energy level given letters s , p, d , f
• symbol = L

Question 16

Second quantum number relating to type of sub shell

Answer 16

L= 
0 - s sub shell 
1 - p sub shell 
2 - d sub shell 
3 - f sub shell

Question 17

Summary of principal and angular momentum quantum numbers with sub shell name

Answer 17

LOOK IN NOTES AT TABLE

Question 18

3rd magnetic quantum number

• what does this refer to
• symbol

Answer 18

• relates to the orientation in space of the orbital
• depend on l because ml takes on any whole number value between -L and +L
  So of L=2 ml could be +2,+1,0,-1,-2
  So this means there are 5 atomic orbitals for L=2

Question 19

4th spin quantum number

Answer 19

• determines the direction of the spin, it is therefore called the spin quantum number
  Has values of -1/2 or +1/2

Question 20

Summary : relating quantum numbers table

Answer 20

Look In notes !

Question 21

Orbital shapes : s orbitals

• describe the shape
• what happen to orbital in higher energy levels

Answer 21

• spherical with size and orbital in higher energy levels ar bigger the the orbital in energy level before it
• energy increases as value of n increase

Question 22

The first shell has only two electrons so has ____ orbital

Answer 22

The first shell has only two electrons so has 1 orbital (1s)

Question 23

Shape of orbitals ; p orbitals

• how many orientations
• describe shape /placement
• which energy levels have p orbitals

Answer 23

• have value L =1 so therefore three orientations
  corresponding to ml = -1, 0, +1 , p sub shells will have 3 p orbitals px,py,pz
• all same shape : approximately dumbbell shaped and at right angles to one another (perpendicular)
• as the first shell has two electrons they go into the s orbital so the second shell and subsequent shells have p orbitals in addition to s

Question 24

The p orbitals are degenerate ,what does this mean ?

Answer 24

Three p orbitals are degenerate meaning they have the same energy as each other

Question 25

Drawing and example quantum numbers for for 2p and 3p orbitals

Answer 25

- drawings : look in notes - quantum numbers for 2p : n=2 , l=1 ml=-1,0,+1 - quantum numbers for 3p : n=3 l=1 ml=-1,0,+1

Question 26

How many electrons does the second energy shell hold - and how is this split into the orbitals

Answer 26

- the second shell can hold a maximum of 8 electrons - the s orbital holds 2 of these - the 3 different p orbitals hold 2 each so in total they hold 6 Therefore the second shell has one s orbital and three p orbitals

Question 27

Shape of orbitals - d orbitals - how many orientations - which energy levels are they in - are they degenerate

Answer 27

- occur in 5 different orientations corresponding to ml= +2,+1,0,-1,-2 and have labels which come from the complex mathematics of quantum mechanics - are first orient in 3rd energy level so are in 3rd energy levels and the following ones - they are degenerate

Question 28

How many electrons can the 3rd shell hold and how

Answer 28

-the 3rd shell can hold a maximum of 18 electrons. Two of these are in an s orbital and three p orbitals hold another 6. The remaining 10 are in d orbitals (so there must be 5 d orbitals as they hold two electrons each)

Question 29

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Answer 29

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Question 30

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Answer 30

-

Question 31

What is electron configuration- and how many ways can it be written

Answer 31

- the arrangement of electrons in the energy levels and orbitals of an atom is called the electronic configuration - three ways - using quantum numbers, orbital box notation , spectroscopic notation

Question 32

What are the three rules for writing orbital box notation

Answer 32

- AUFBAU : the aufbau principle states that when electrons are placed into orbitals the energy levels are filled up in order of increasing energy eg : 1s is filled before 2s. The orbitals you need to know in order of increasing energy are 1s, 2s, 2p,3s,4s,3d,4p - PAULI - the Pauli exclusion principle states that no two electrons in the one atom can have the same set of 4 quantum numbers. As a consequence no orbital can hold more than two electrons and the two electrons must have opposite spins (if the two electrons are in one orbital , then both electrons must have the same quantum numbers n, L and ml, but they will have different spin numbers (either +1/2 or -1/2) HUND- Hunds rules states that when there are degenerate orbitals in such shells (such as in 2p) electrons fill each one singly with spins parallel before pairing occurs

Question 33

Writing electrons configuration in spectroscopic notation and orbital box notation

Answer 33

Look at notes / textbook (you should already know how to do this )

Question 34

The structure of the periodic table depends upon the ___________ ____________ of the elements

Answer 34

The structure of the period table depends upon the electronic configuration of the elements

Question 35

The chemical properties of an element are dictated by the __________ in _________ shells Therefore the periodic table relates configuration to __________

Answer 35

The chemical properties of an elements are dictated by the electrons in the outer shells Therefore the periodic table related configuration to properties

Question 36

What is s , p , d , f block elements of the periodic table

Answer 36

- these are elements located in in certain block of the periodic table - s block elements, are where the highest energy level electrons are found in the s subshell

Question 37

What is ionisation energy

Answer 37

The ionisation energy of an element is the energy required to remove one mole of electrons from one mole of gaseous atoms. The second and subsequent ionisation energies refer to removal of further moles of electrons

Question 38

Ionisation energy graph and explanation

Answer 38

Notes

Question 39

There a special stability associated with a filled sub shell or a _____ filled sub shell

Answer 39

There is a social stability associated with a filled sub shell or a half filled sub shell For example the p sub shell when it contains three or six electrons. Likewise the d sub shell is most stable when it contains five or ten electrons.

Question 40

How does more stable electron configuration effect ionisation energy

Answer 40

- the more stable the electron configuration , then the more difficult it is to remove an electron and therefore the ionisation energy is higher