3 Atomic Structure PUPILS

OK, we know that all stuff is made up of the 92 naturally occurring _____________

BUT what does each of these elements consist of? _____________________

Atomic Structure

Protons

Electrons

Neutrons

So, what are atoms made up of?

ProtonsThese are found at the centre or NUCLEUS of the atom (so they are nucleons)

Electrons Are found at different distances around the nucleus

NeutronsAre also found in the nucleus of the atom (and are also nucleons)

These are the simplest SUBATOMIC particles.

+-

The simple model of a hydrogen atom was proposed in 1913 by Niels Bohr.

Things get more complicated with bigger atoms - which element is this an atom of?

Extra: Investigate the life and work of this extremely influential physicist

Definitions:

The PROTON NUMBER (AKA: Atomic Number) is the

___________________________________________________________

The proton number tells us which element the atom belongs to.

The NUCLEON NUMBER (AKA: Mass number) is the

__________________________________________________________

Sub-Atomic Particle Relative Mass Charge Discovery

Proton 1909 - Rutherford

Electron 1897 - JJ Thompson

Neutron1920 Rutherford suggests its existence/1932 James Chadwick discovers it

Discovery of the electronhttps://www.youtube.com/watch?v=Rb6MguN0Uj4

Discovery of the Nucleushttps://www.youtube.com/watch?v=dNp-vP17asI

Videos: Basic Atomic Structure

Relative masses and charges of the simplest subatomic particles….

1 +1

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1 0

Write the symbols for the following elements….

Sodium

Using symbols….

IMPORTANT: By definition, an ATOM is always neutral so it must have the same number of

_________________________ and __________________________

Video: Atomic Number

Read pp22-23 Q1-3

Na1123

Helium

Calcium

Why is Chlorine different from the rest of the elements in your periodic table?

Is reality, Chlorine exists as 2 different atoms….

ISOTOPES

NB1. Isotopes of an element have the same chemical properties because chemical properties only depend on the number of electrons that an atom has!

NB2. The physical properties of isotopes can be different, eg. density,.

Explain why…

_____________________________________________________________

______________________________________________________________

Learn this definition: ISOTOPES of an element are atoms with the same proton number (same number of protons) and different nucleon numbers (different numbers of neutrons).

ISOTOPES can be 2 types: radioactive and non-radioactive

Radioactive isotopes are UNSTABLE and spontaneously break up to give other particles and radiation (which can be high energy and dangerous).

Non-radioactive isotopes are STABLE (they do not change over time).

Radioactive isotopes have very interesting properties and some important uses and applications:

USES of Radioactive Isotopes

Medical uses: To treat cancer - “radiotherapy”

Watch video: Isotopes in MedicineHow are tracers used?

Non-medical uses

- To find leaks in pipes- To kill germs and bacteria in food- Carbon dating- Fuel in nuclear power stations (U-235)

Read pp24-25 Q1-3

Where do the electrons go in the atom?

Electrons go into “shells” or “energy levels” around the nucleus.

Each shell can take a maximum number of electrons, as shown in the following table:

Shell * How many electrons fit?

1 2

2 8

3 18

4 32

*This is the same as the PERIOD in the periodic table (the number down the left hand side or the number of the ROW that the element is in).

12

4

6

3

5

At IGCSE level, we only have to be able to say where the electrons are for the first 20 elements.

This is called the ELECTRONIC CONFIGURATION

12

2,1 2,8

2,8,1 2,8,8

2,8,8,1 2,8,8,2

2,2 2,3 Etc

2,8,2 2,8,3 Etc

NB1. The noble gases have a FULL OUTER SHELL of electrons and this makes them very STABLE and very UNREACTIVE.

This is a important point!

Name all of the noble gases

NB2. The electrons in the outer shell are called VALENCY ELECTRONS

You can easily see how many valency electrons an atom of an element has by looking at its GROUP NUMBER - the number at the top of the periodic table.

Element Symbol # of Protons

# of Electrons

# of Neutrons

Electronic configuration

Consider the following table:

Read pp26-27 Q1-3Video: Basic Atomic Structure Revision

Hydrogen H 1 101

Lithium Li 3 3 4 2,1

Potassium K 19 19 20 2,8,8,1

Read pp28-29Definition: What is an ELEMENT?

Elements, Compounds and Mixtures

What are CHEMICAL BONDS?

What is a COMPOUND?

YOU MUST LEARN THESE DEFINITIONS!

pp28-29 Q1-3

What is a MIXTURE?

Put the following substances into the correct column in the table.

Write their chemical formula if you know it…

HydrogenWaterCola Cao (or Nesquik as you prefer. Sobre los gustos…)BromineAirSodium ChlorideAmmoniaCrude OilPetrol (Octane)UraniumCarbon dioxideNitrogenBleachChlorineBrass

ELEMENT COMPOUND MIXTURE

HydrogenBromineUraniumNitrogenChlorine

WaterSodium ChlorideAmmoniaPetrol (Octane)Carbon dioxide

Cola CaoAirCrude OilBleachBrass

Metals Non-Metals

Examples

Physical Properties

Chemical Properties

Metals and Non-MetalsRead pp30-31 and compare and contrast the properties of metals and non-metals in the following table…

pp31-32 Q1-3/Questions pp32-33

- What holds stuff together

Atoms usually form bonds with each other to become STABLE.

There are exceptions to this in the periodic table.

Bonding

Which group of elements are already very stable?

SO,…..when atoms take part in chemical reactions they do so in order to try to achieve the

NOBLE GAS ELECTRONIC CONFIGURATION (NGEC)

Why?

When chemicals react, new BONDS are formed between the particles involved.

There are 3 types of bonding that we will come across:

• Ionic Bonding• Covalent Bonding• Metallic Bonding

IONIC BONDING

Ionic compounds form when metals (left hand side of periodic table) react with non-metals (right hand side of the periodic table).

eg. Sodium and Chlorine

What must Sodium do in order to achieve a stable NGEC?

A SODIUM ION is formed

NB. An ION is charged particle

What must Chlorine do to achieve a NGEC?

A CHLORIDE ION is formed

NB. When a non metal element forms a simple ion, it adopts the ending “ide”

So the electron from the Sodium atom is TRANSFERRED to the Chlorine atom

Once the oppositely charged ions have formed, what do they do?

NB: These diagrams are called “dot and cross diagrams” for obvious reasons. The use of dots and crosses is helpful to show where the electrons came from and where they have gone.

This is called a crystal…..

Once lots of ions are formed, they come together to form a giant 3D structure…

Now let’s do the same with another Group 1 and another Group 7 element

pp34-35 Q1-3

Tricky example: Magnesium and Chlorine

Lithium Fluoride, LiF is formed

Magnesium Chloride, MgCl2 is formed

NB. In most cases you only need to show the outer shell of electrons - the valency shell - when you form ionic compounds

IGCSE QUESTION:

The full diagram would look like this

But only outer shell electrons are required to get the marks

Key ideas:

• Ions form when atoms lose or gain electrons to get a stable NGEC

•Once the ions have formed the opposite charges attract to form an IONIC BOND

•This causes the ions to line up to form a LATTICE of alternating positive and negative charges

•Ionic bonds form between METAL IONS AND NON-METAL IONS

Once you can predict which ions will be formed by atoms of an element, you can use the information to work out the CHEMICAL FORMULAE of IONIC COMPOUNDS

In the following empty periodic table, fill in the ions formed by the elements…

H+

Na+ Cl-

O2-Al3+

Ba2+

P3-

Pb2+

Sn2+

Zn2+

Ag+

Cu2+Cu+Fe2+

Fe3+

1

2 3 4 5 6 7

0

Try to predict the chemical formulae of the following:

1.Lithium Chloride

2.Sodium Bromide

3.Calcium Chloride

4.Potassium Oxide

5.Aluminium Fluoride

6.Aluminium Oxide

The next type of bonding that exists in chemical elements and compounds is…

COVALENT BONDING In this type of bonding, atoms SHARE electrons with each other in order to achieve something closer to a NGEC

Hydrogen molecules Chlorine Molecules

Definition: The VALENCY of an atom is the number of electrons that must be lost or gained in order to achieve a NGEC

Water molecules

Methane

Ammonia

Hydrogen Chloride

pp36-37 Q1-3

DEFINITION (LEARN):

More difficult covalent compounds….

Oxygen

Nitrogen

EtheneEthanol

Task - memorise the structures of the above molecules so that you can identify them in this online quiz

Carbon DioxideMethanol

Structure and properties of IONIC and COVALENT COMPOUNDS

We need to know the differences between ionic and covalent (sometimes called “molecular”) substances…

Property IONIC COMPOUNDSCOVALENT

COMPOUNDS

Solubility in polar solvents (eg. water) High Low

Solubility in non-polar (organic) solvents (eg. cyclohexane)

Low High

Volatility - is it volatile? (does it easily evaporate?)

Low High

Electrical conductivity when solid Low Low

Electrical conductivity when liquid or in solution High Low

Melting and boiling points High Low

Can we explain the differences in melting and boiling points of IONIC and COVALENT compounds?

A lot of energy is required to break down the strong ionic bonds in the giant 3D lattice so ionic compounds have a high melting point

Only weak intermolecular forces exist between covalent molecules so little energy is needed to melt and boil them!

pp40-41 Q1-3

MACROMOLECULES

What are allotropes?

Definition:

“Giant covalent structures”

GRAPHITE DIAMOND SILICON DIOXIDEDescription: Description: Description:

Properties: Properties: Properties:

Uses: Uses: Uses:

pp42-43 Q1-3

Black shiny solid Layers of Carbon atoms Each C atom joined to 3 others Hexagons formed

Transparent colourless crystals Each C atom joined to 4 others A tetrahedral structure formed A 3D giant lattice created

Similar to diamond Tetrahedral structure Each Si atom joined to 4 O atoms Each O atom joined to 2 Si atoms 3D giant lattice created

High mpt and bpt Conducts electricity Layers can slide over each other

High mpt and bpt Very hard

High mpt and bpt Hard

Dry lubricant(locks) Pencil “lead” Motors and generators

Cutting an drilling tools Jewellery

Glass manufacture

The last type of bonding that we need to look at, and is perhaps the most special is…

Metallic BondingEach metal atom donates its valency electrons to form a DELOCALISED SEA OF ELECTRONS.

This sea of mobile electrons flows around a LATTICE OF POSITIVELY CHARGED METAL IONS.

NB. It is the attraction between the lattice of metal ions and the sea of electrons that holds the metal together - this is Metallic Bonding, and acts in all directions

We can use these ideas to explain the curious and wonderful properties that metals have.

They conduct electricity because…

They conduct heat because….

pp44-45 Q1-3 End of chapter questions

They are malleable and ductile because…

Other properties…Many metals have high melting and boiling points as lots of energy is required to overcome the metallic bonding.

Many are also hard and dense

The layers of ions can slide over each other and adopt new shapes. This is possible because the metallic bonding acts in all directions so is not broken as the lattice changes shape.