Elements of Life Lesson objectives Introduction to the course? How will you best keep up with the work? Revising the atomic structure. Key words Protonelectronneutronisotope.

Elements of Life

Lesson objectives

• Introduction to the course?• How will you best keep up with the work?• Revising the atomic structure.

Key words

Proton electron neutron isotope

Alpha particle beta particle

StarterWork in pairs on old fashioned O level questions on

atomic structure – 15 minutes

Amounts of substanceLesson objectives

• What is the relative atomic mass (RAM) of an element?

• How do we use RAM to discuss the amounts of substance we have in?

• Can we link real measurable masses with the number of atoms for any substance?

Key words

The mole relative atomic mass (RAM)

Relative molecular mass (RMM) Avogadro’s constant

StarterReading pages 1-4 in Chemical ideas

The mole

1 mole of a substance is the amount of substance which contains as many formula units (atoms, molecules or groups of ions) as there are atoms in 12 g of 12C.

• The number of particles in one mole is called the Avogadro constant. It is equal to 6.022 x 1023.

Molar mass

• The mass of one mole is the equal to the relative atomic mass in grams.

• It is called the molar mass and has units of g mol–1.

• For example, the molar mass of carbon is 12 g mol–1.

The amount of a substance

• The amount of substance in grams, the amount of substance in moles, and the molar mass are related:

amount in moles = mass in grams molar mass

mass in grams = molar mass x amount in moles

Chemical Formulae

• A chemical formula represents the ratio of the number of atoms of those elements in that chemical substance.

• The molecular formula is the formula of a molecule of a substance. Eg C2H6 ethane

• An empirical formula is that formula in its simplest ratio, but may not represent the actual molecule. (CH3)

Homework

Problems EL1.1

• Answer for handing in Questions 5-8.

• 12R Monday 15th September

• 12P Tuesday 16th September

Balancing chemical equations

Lesson objectives

• Using the state symbols for all reactants and products.

• Practising balancing equations so all the atoms present in the reactants are present in the products.

• Using equations to work out reacting masses.

Key words

Reactants products aqueous solution

Homework

Problems EL1.3

• Complete questions 1-3

• Pre-read Chemical story EL2 and Practical EL1.2 How much iron is in a sample of an iron compound?

Return Thursday 25th September

Making standard solutions

Lesson objectives

• Learn how to use analytical apparatus to obtain accurate and precise results.

• Appreciate where there are natural errors/uncertainties to consider in your experiments.

Key words

Volumetric flask precision accuracy quantitative

volumetric analysis

Volumetric analysis

Lesson objectives

• Practise using analytical apparatus to obtain accurate and precise results.

• Use the results to calculate the % iron in the iron sulfate sample.

Key words

Volumetric pipette burette precision accuracyquantitative volumetric analysis

Homework

EL1.2 Answer questions on the sheet

• Calculate the % iron in your sample.

• Show your working using the stages described on the sheet.

• Compare your result with the 14.3% expected result.

• Complete questions 1-3

Hand in: 12R Friday 3rd October

12P Wednesday 1st October

Models of the atom

Lesson objectives

• Recall the structure of the atom.• How does a mass spectrometer work?• Why is the relative abundance of isotopes of an

element valuable information?

Key words

Nucleus proton neutron electron

mass spectrometer relative abundance

Useful websites

http://www.chemguide.co.uk/analysis/masspec/howitworks.html

Definitions• Explain the terms:

1. The atomic number.

2. The relative atomic mass (r.a.m.)

3. The mass number of an isotope of an element.

4. The relative isotopic mass

5. Isotope

Mass spectrometer

The abundance of the isotopes• The relative sizes of the peaks gives you a

direct measure of the relative abundances of the isotopes.

• The tallest peak is often given an arbitrary height of 100 - but you may find all sorts of other scales used.

• You can find the relative abundances by measuring the lines on the stick diagram.

• In this case, the two isotopes (with their relative abundances) are:

boron-10 23boron-11 100

The mass spectrum for boron

• The two peaks in the mass spectrum shows that there are 2 isotopes of boron - with relative isotopic masses of 10 and 11 on the 12C scale.

Working out the relative atomic mass

• The relative atomic mass (RAM) of an element is given the symbol Ar and is defined as:

• The relative atomic mass of an element is the weighted average of the masses of the isotopes relative to 1/12 of the mass of a carbon-12 atom.

• A "weighted average" allows for the fact that there won't be equal amounts of the various isotopes. The example coming up should make that clear.

Working out the relative atomic mass

• Suppose you had 123 typical atoms of boron. 23 of these would be 10B and 100 would be 11B.

• The total mass of these would be

(23 x 10) + (100 x 11) = 1330• The average mass of these 123 atoms

would be 1330 / 123 = 10.8 (to 3 significant figures).

• 10.8 is the relative atomic mass of boron.

Pre-read for next lesson

• In Chemical Ideas we will be looking at EL2.2 Radioactivity next lesson.

• Pre-read – Section 2.2 pg18-23

• General reading

• Read Mass Spectrometer EL4.2

• Pg 139-144

Radioactivity and nuclear processes

Lesson objectives

• Recognise the changes in the nucleus following radioactive decay.

• Learn how to represent these processes with nuclear equations?

Key words

Nuclear fusion half life activity

radioactive decay emissions alpha beta gamma

Starter

Answer EL4.2 Isotopic abundance and RAM

Pre-read

• Read EL2.2 Half lives and nuclear fusion

Radioactive activity and half life

Lesson objectives

• What process powers the sun?• Use the concept of the half life to describe

radioactive decay.

Key words

Nuclear fusion half life activity

radioactive decay emissions

Simulating radioactive decay

1. Turn over the block of 100 dice.2. Count how many dice have the coloured

side facing up. These are the atoms that have decayed in the first minute.

3. Take these out of the sample as they have decayed.

4. Return the remaining unstable atoms to the tray and repeat the process.

5. Create a table with time and activity.

Radioactive decayTime (minutes) Unchanged atoms Atoms decayed

1

2

3

4

5

6

7

8

9

10

Plot a graph of

1. Plot a graph of unchanged dice (undecayed radioactive nuclei) in the sample against the time.

2. Work out 3 values of “radioactive half life” based on your data.

3. Combine your results with other groups and plot a new graph using the average results.

4. How do the half life results from the class average compare to your initial graph?

Radioactive decayTime (minutes) Unchanged atoms MEAN

1

2

3

4

5

6

7

8

9

10

An exponential radioactive decay curve

Homework

• Revise for a Test next week covering:

• atomic structure,

• calculating relative atomic mass,

• Balancing equations

• using moles to calculate amounts of substances

• Nuclear reactions and equations.

Nuclear fusion and the use of radioactive tracers

Lesson Objectives• What powers the sun?• Practise writing nuclear equations.• Understanding half lives for uses in

geological dating and radioactive tracers for health applications.

KeywordsNuclear fusion Radioisotopesradioactive tracers

Flame tests and quantum levels

Lesson Objectives• Can we identify an element by looking at its

burning flame colour?• How do we know Jupiter has neon gas in its

atmosphere, when no one has been there?• What is the difference between an

absorption and an emission spectra?

KeywordsQuantum levels spectroscopy

Flame tests

Compound Flame colour

Sodium

Potassium

Copper

Lithium

Magnesium

Calcium

Strontium

Flame testsCompound Flame colour

Sodium Yellow

Potassium Lilac

Copper Green

Lithium Red

Magnesium White

Calcium Orange-red

Strontium Bright red

Spectra and line spectra

Light and electronsLesson Objectives• What was Bohr’s theory on quantisation of

energy?• Can we explain frequency of light emitted or

absorbed with movements of electrons in the atom?

• Can we calculate the energy jump of the electron if we know the frequency of the light?

KeywordsElectromagnetic spectrum spectroscopyExcited ground state energy levels

Evidence for Energy levels

Evidence for Energy levels

Pre Reading

• Chapter 6.1 Light and electrons

• Pages119-123

Electronic structureLesson Objectives• Can we know where an electron is at

any moment in time?• What is an electron orbital?• How does an orbital relate to energy?• Where is our evidence for these ideas?

Useful websites

http://www.chemguide.co.uk

Keywords“Heisenberg Uncertainty Principle”

Most popular pictures of the atom are wrong!!

• These images show electrons moving around a nucleus like planets around a sun.

• They are wrong and come from an old idea of the atoms.

What about electron orbit diagrams?

• Eg. Sodium• These are

fine if you know the circles are not representing where the electrons are moving.

Energy Levels

• The circles represent energy levels.

• The electrons closest to the nucleus have the lowest energy.

• The eight on the next level have a higher energy.

• The one on the outer circle has the highest energy.

Hydrogen's electron - the 1s orbital

• Suppose you had a single hydrogen atom and at a particular instant plotted the position of the one electron.

• Soon afterwards, you do the same thing, and find that it is in a new position.

• You have no idea how it got from the first place to the second.

• The drawing represents where the electron will be 95% of the time.

Fitting electrons into orbitals

Electrons in boxes• A 1s orbital holding 2

electrons would be drawn as shown on the right, but it can be written even more quickly as 1s2.

The 2s orbital

• It is similar to the 1s orbital except the region where there is the greatest chance of finding the electron is further from the nucleus.

• The 2s ( and 3s and 4s etc) electrons spend their time closer to the nucleus than you would expect.

The p orbitals• At the first energy

level, the only orbital available to electrons is the 1s orbital, but at the second level, as well as a 2s orbital, there are also orbitals called 2p orbitals.

• The p orbitals point in a particular direction.

Three p orbitals

• At any one energy level there are 3 equivalent p orbitals.

• These are arbitrarily given the symbols px, py and pz.

• The p orbitals at the second energy level are called 2px, 2py and 2pz. There are similar orbitals at subsequent levels - 3px, 3py, 3pz, 4px, 4py, 4pz and so on.

d and f orbitals

• At the 3rd level there 2 other sets of orbitals at higher energy levels.

• There are a set of FIVE d orbitals as well as 3s and 3p. (Total 9 orbitals)

• At the fourth level as well as 4s, 4p and 4d orbitals there are SEVEN f orbitals. (Total 16 orbitals)

Fitting electrons into orbitals

• Electrons fill low energy orbitals before higher ones.

• Where there is a choice between equivalent orbitals, eg 3p, they fill orbitals singly.

• This is Hund’s rule.

Spectra and line spectra

Evidence for Energy levels

Filling Electrons into Orbitals

Lesson Objectives• Can we use our understanding of orbitals to

explain the electronic structure of elements?• Using the electronic structure shorthand.• How are the ionisation energies defined?• Where is our evidence for these ideas?

Useful websites

http://www.chemguide.co.uk

KeywordsQuantum levels ionisation energy

Fitting electrons into orbitals

• Electrons fill low energy orbitals before higher ones.

• Where there is a choice between equivalent orbitals, eg 3p, they fill orbitals singly.

• This is Hund’s rule.

Fitting electrons into orbitals

Electrons in boxes• A 1s orbital holding 2

electrons would be drawn as shown on the right, but it can be written even more quickly as 1s2.

The Exceptions to the rule

• Chromium is [Ar] 3d5 4s1 NOT [Ar] 3d4 4s2

And• Copper is [Ar] 3d10 4s1 NOT [Ar] 3d9 4s2

• Because an atom is more stable if it has a half filled or a filled set of 3d-orbitals, and a single 4s electron, rather than four or nine 3d-electrons and two in the 4s-orbital.

Electronic structure and ions

Lesson Objectives• How are the ionisation energies defined?• Where is our evidence for these electronic

orbital structures?• Understanding patterns in ionization

enthalpies across periods and down groups.• Looking for patterns across a period.

KeywordsIonization enthalpy ionisation energyNuclear charge Periodicity

Ionisation energies

• Ionisation energy is the energy needed to remove an electron from an atom, ion or molecule. The units are normally kJmol-1.

Definition• The first ionisation energy of an

element is the energy required to remove one electron from the ground state of each atom of a mole of gaseous atoms of that element.

Pattern for the 1st ionization energies for first 90 elements

Reasons for the peaks in the ionisation energies of the elements?

• Peak for He - full outer shell - 1s2 • Peak for Be - full sub-shell - 1s2 2s2 (small peak

due to slight increase in stability as 2s2 is full) • Peak for N - half full p sub-shell - 1s2, 2s2, 2p3

(peak is even smaller for the same reasons) • Large peak for Ne - full quantum level; all sub-

shells are filled - 1s2, 2s2, 2p6 • Same pattern for d sub-shell. Elements with d5

will have a higher ionisation energy than d4 due to a half filled d sub-shell.

The order of Stability is:

• Full quantum shell (largest peak)

• Half full p sub-shell

• Full s sub-shell (small peak)

• The order of stability for members of a group of elements are the result of their

• similar electron arrangement.

The Second Ionisation energy

Definition• The second ionisation energy is the

energy required to remove one electron from each ion of a mole of gaseous singly charged positive ions of that element.

Evidence for the existence of quantum shells

• Successive ionisation energies

• Consider the Successive ionisation energies for the first 20 elements.

• Plot a graph of Energy (KJmol-1) again Ionization energies numbers.

Useful websites

• S-Cool – A chemistry

• Chemguide.co.uk

• http://www.docbrown.info/page19/saltersASchemistry.htm Salters AS chemistry

• www.Revision-notes.co.uk

• En.Wikibooks.org Salters AS chemistry

• Thestudentroom.co.uk/wiki

Developing our ideas about the atom

Lesson Objectives• Who are the key scientists and what

are their contributions to our ideas and models about the atom?

Keywords

Develop a presentation about a scientist

Choice of scientists1. Joseph J. Thomson2. Hans Geiger, Ernest Marsden and Ernest

Rutherford3. Niels Bohr4. Henry Moseley5. James Chadwick6. Erwin Schrödinger 7. Werner Heisenberg

PresentationsScientists 12P 12RJoseph J. Thomson Amandeep,

AmandeepShanice, Alex

Hans Geiger, Ernest Marsden and Ernest Rutherford

Rehana, Noor, Helena

Hitesh, Ben

Niels Bohr Karan, Randeep Sara, Basmah, PJ

Henry Moseley Saqlain, Paul, Aadil Abishek, Bardeep

James Chadwick Inderpreet, Simran Tom, Andy

Erwin Schrödinger Josh, Faiz, Joel Rebecca, Arsalan, Nadia

Werner Heisenberg Kadir, Jack, Michael Dhawal, Zaman, Ibrahin

Contents

• Who are you?

• When you did the work you will describe?

• What you already knew about the atom?

• What you did?

• What you found out?

• What conclusions you drew from your results?

Chemical BondingLesson Objectives• Understand why some elements form ionic

compounds and non-metals form covalent bonds in compounds.

• How to represent bonds using dot-cross diagrams.

• What is a dative covalent bond?

KeywordsCations anions ionic bonding Bonding pairs“electrostatic attraction” Dot-cross diagrams“Dative covalent bond”

Pattern for the 1st ionization energies for first 90 elements

Ionic Bonding PoemHow do I long for a full outer shell!

being chlorine having seven, is a horrid hellbut my name is sodium and I have one spare!

I want to lose it, can we not share?No? for are we not a perfect matchchuck it to me, I promise to catch

then we can live our separate waysand live with full shells to the end of our days!

and so our tale comes to an endas positive and negative we shall remain friends.

(anon Y11 student, Whitby Community College, Oct 31st 2002)

Electronegativity and polar bonds

Lesson Objectives• Why are some covalent bonds polar?• What is “electronegativity” and how

it helps us predict the polar nature of some covalent compounds?

Keywords“Dative covalent bond”

electronegativityPolar bonds dipole delta, δ

Metallic bonding and chemical formulae

Lesson Objectives• Metallic bonding in metals to achieve

stability.• How to determine chemical

formulae?

Keywordslattice delocalised electrons

Shapes of molecules

Lesson Objectives• Can we predict the 3 dimensional

shape of molecules from their formula and an understanding of bonding pairs?

KeywordsElectron pair repulsion tetrahedral planar planar triangular bipyramidal octahedral

Methane has a tetrahedral shape

• A line represents a bond in the plane of the paper.

• A dashed line represents a bond pointing into the paper.

• A wedge represents a bond coming out of the plane of the paper.

Chemistry of the Group 2 metals

Lesson Objectives• Describe and compare the following properties

of the elements and compounds of Group 2 metals:

• reactions of the elements with water.• acid–base character of the oxides and

hydroxides.• thermal stability of the carbonates.• solubilities of hydroxides and carbonates.

KeywordsThermal stability solubility

Periodic patterns across the Periodic Table

Lesson Objectives• Use information to describe periodic trends in

the properties of elements in terms of melting and boiling points.

• Understand how Mendeleev developed the Periodic table by leaving gaps and rearranging some elements from their atomic mass order.

Starter

EL2.3 What type of properties do different structures have?

KeywordsPeriodicity Mendeleev

Homework

• Prepare for a Test on Electronic Structure, chemical bonding and shapes of molecules

Test: 3rd December

• Pre-read 11.2 The s block: Groups 1 and 2

Thursday 11th December