1.1d Particles in the atom and atomic radius

• Chemistry
• Secondary Education
• Age 12,13

AS Level Chemistry 9701

Topic 1.1 Particles in the atom and atomic radius

24 August 2023

• determine the electronic configuration of atoms and ions given the atomic or proton number and charge using the FEC, SEC, and EBN
• explain the electronic configurations in terms of energy of the electrons and inter-electron repulsion  
• describe and sketch the shapes of s and p orbitals  
• describe a free radical 

We are learning to:

AS Level Chemistry 9701

Topic 1.1 Particles in the atom and atomic radius

24 August 2023

• Recall the meaning of "Ionisation energy" and what it does
• Draw a planetary model of a Calcium atom at the ground state following its electron configuration.

Recap of our lessons

AS Level Chemistry 9701

Topic 1.1 Particles in the atom and atomic radius

24 August 2023

atomic nucleus

lobe

T O   D O:

• Navigate the simulation found at Atomic Orbitals simulation. Use this as a blueprint for your model.
• Include information such as shape, size, orientation, and amount of energy. 
• Share your models with the class.

s and p Orbitals: 3-D Model-making 

www.chemtube3d.com

AS Level Chemistry 9701

Topic 1.1 Particles in the atom and atomic radius

24 August 2023

Writing electron configurations

Principles involved in EC

• Aufbau Principle = German for 'building up
• Madelung's Rule
• Hund's Rule of Maximum Multiplicity

Aufbau Principle

1s<2s<2p<3s<3p<4s<3d<4p<5s<4d<5p<6s<4f<5d<6p<7s<5f<6d<7p

•  Electrons occupy orbitals in order of increasing energy.

Madelung's Rule

Hund's Rule

• When electrons occupy degenerate orbitals, they must first occupy the empty orbitals before double occupying them.

Electron Box Notation

• Electrons = small spinning charges
• Electrons with similar spin = repel each other 
• (a.k.a. Spin-pair repulsion)

Electron Box Notation

• Even though there is repulsion between negatively charged e- (inter-electron repulsion) they occupy the same region of space in orbitals. 

Electron box notation

• Lithium
• Beryllium
• Boron
• Carbon
• Nitrogen
• Oxygen
• Fluorine
• Neon

AS Level Chemistry 9701

Topic 1.1 Particles in the atom and atomic radius

24 August 2023

Free Radicals

• Free radical - a species with one or more unpaired electrons.

Self-Assessment of Learning

T O    D O:

• Identify two ideas you do not understand quite well in our sessions.
• Ask someone who can explain and write the explanations in your notebook.
• Verify your learning from a classmate by sharing it with the teacher.

AS Level Chemistry 9701

Topic 1.1 Particles in the atom and atomic radius

24 August 2023

• define and use the term first ionisation energy, IE1  
• explain the reason for ionisation energies 
• identify and explain the trends in ionisation energies across a period and down a group of the Periodic Table  

We are learning to:

• explain the factors influencing the ionisation energies of elements   
• construct equations to represent first, second and subsequent ionisation energies  
• identify and explain the variation in successive ionisation energies of an element  

We are learning to:

Ca (g) → Ca+(g)  +  e-                 IE1 = + 590 kJ mol-              @298 K , 101 kPa

Recap of lessons

Ca (g) → Ca+(g)  +  e-                 IE1 = + 590 kJ mol -              @298 K , 101 kPa

Recap of lessons

• ionisation equation

• ❓Question: In a statement form, what does the equation tell you? 

                                      Ca (g) → Ca+(g)  +  e-                 

• Translate the given equation into a sentence using the key terms: energy, remove, one mole of electrons, gaseous. 

• Share your output with a classmate

Challenge 🏆

                                      Ca (g) → Ca+(g)  +  e-                 

• The first ionisation energy of Calcium is the energy required to remove one mole of electrons from one mole of the gaseous Calcium.

Translation 📝

docs.google.com

• Ionisation energy - the amount of energy required to remove one mole of electrons from one mole of gaseous atoms to form one mole of gaseous ions. 
•  measured under standard conditions @298 K , 101 kPa
• unit of measure - kilojoules per mole (kJmol-)

Ionisation Energies

Ca (g) → Ca+(g)  +  e-           IE1 = + 590 kJ mol -                   @298 K , 101 kPa         

• The first ionisation energy of Calcium is the energy required to remove one mole of electrons from one mole of the gaseous Calcium to form one mole of 1+ ions.

First Ionisation Energy 

Need for Energy

• ❓Question: Is energy really needed to remove valence electrons? 

Is energy needed to remove 

valence electrons?

Yes.

No.

Need for Energy

Attractive force

Attractive force

• ❓Question: Can you break this attractive force?

Attractive force

ionisation energy

• Nuclear charge
• Shielding
• Atomic or ionic radius
• Spin-pair repulsion

Factors affecting the magnitude of ionisation energy

• increases with increasing proton number
• stronger attractive force between the protons and electrons
• greater nuclear charge = higher ionisation energy needed

Factor 1- Nuclear charge

• more shells = more shielding effect due to inter-electron repulsion
• more shielding = weaker attractive force
• more shielding = requires lower ionisation energy

Factor 2 - Shielding

• ❓Question: Which has more shielding effect?

Which has more shielding effect?

• larger radius = outer electrons are farther away from the nucleus
• greater distance from the nucleus = weaker attractive force
• weaker attractive force = less ionisation energy needed 

Factor 3 - Atomic or ionic Radius 

• Spin-pair repulsion happens when the electron being removed is spin-paired with another electron in the same orbital.
•  Non-spin-paired electrons are more difficult to remove, so they require more ionisation energy.

Factor 4 - Spin-pair repulsion

Summary of Factors

AS Level Chemistry 9701

Topic 1.1 Particles in the atom and atomic radius

24 August 2023

T O   D O:

• Using the given chart on the first, second, third, and fourth ionisation energies of elements, construct a bar graph.
• The x-axis is the element in symbol with atomic number, and the y-axis is the first ionisation energy, in kJ mol -.
• Share your graphs with the class.

Activity 12—Bar Graph Making (First ionisation energies of elements from periods 1-3)

• Ionisation energies show periodicity.

Across a period 

- nuclear charge increases

- atomic radius decreases

- shielding remains constant

- gets harder to remove an electron

- ionisation energy increases

Conclusions from the graphs