1. EdExcel Additional Science
19/09/2018
EdExcel Additional Science
In Your Element
W Richards
The Weald School

2. The structure of the atom
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The Ancient Greeks used to believe that everything was made up of very small particles. I did some experiments in 1808 that proved this and called these particles ATOMS:
Dalton
ELECTRON – negative, mass nearly nothing
PROTON – positive, same mass as neutron (“1”)
NEUTRON – neutral, same mass as proton (“1”)

3. Mass and atomic number 4 He 2
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Particle
Relative Mass
Relative Charge
Proton 1 +1
Neutron
Electron
Very small -1
MASS NUMBER = number of protons + number of neutrons He 2 4
SYMBOL
PROTON NUMBER = number of protons (obviously)

4. How many protons, neutrons and electrons?
Mass and atomic number
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How many protons, neutrons and electrons? 1 11 16 H B O 1 5 8 23 35
238 Na Cl U 11 17 92

5. Isotopes
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An isotope is an atom with a different number of neutrons:
Notice that the mass number is different. How many neutrons does each isotope have? O 8 16 O 8 17 O 8 18
Each isotope has 8 protons – if it didn’t then it just wouldn’t be oxygen any more.

6. Relative Atomic Mass
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The relative atomic mass of an element is the average mass of a sample of those atoms.
For example, naturally-occuring chlorine consists of 3 parts 35Cl for every 1 part 37Cl, so the atomic mass of chlorine is:
(3 x x 37) / 4 = 35.5
Q. What is the relative atomic mass of magnesium, which consists of 8 parts 24Mg, 1 part 25Mg and 1 part 26Mg?

7. Electron structure 39 K 19 Consider an atom of Potassium:
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Consider an atom of Potassium:
Nucleus K 19 39
Potassium has 19 electrons. These electrons occupy specific energy levels “shells”…
The inner shell has __ electrons
The next shell has __ electrons
The next shell has the remaining __ electron
Electron structure
= 2,8,8,1

8. Trends in Group 1 Consider a sodium atom: +
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Consider a sodium atom: +
Take away one of the electrons (oxidation)
Sodium ion
Now consider a potassium atom: +
Take away one of the electrons (oxidation)
Potassium ion
Potassium loses its electron more easily because its further away – potassium is MORE REACTIVE

9. Trends in Group 7 Consider a flourine atom: -
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Consider a flourine atom: -
Add an electron (reduction)
Flouride ion
Now consider a chlorine atom: -
Add an electron (reduction)
Chloride ion
Chlorine doesn’t gain an electron as easily as flourine so it is LESS REACTIVE

10. Periodic Table Introduction
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Periodic Table Introduction

11. Horizontal rows are called PERIODS
Periodic table
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Mendeleev
The periodic table arranges all the elements in groups according to their properties.
Vertical columns are called GROUPS
Horizontal rows are called PERIODS

12. The Periodic Table
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Fact 1: Elements in the same group have the same number of electrons in the outer shell (this corresponds to their group number) H He Li Be B C N O F Ne Na Mg Al Si P S Cl Ar K Ca Fe Ni Cu Zn Br Kr Ag I Xe Pt Au Hg
These elements have __ electrons in their outer shells
These elements have __ electrons in their outer shell
E.g. all group 1 metals have __ electron in their outer shell

13. The Periodic Table
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Fact 2: As you move down through the periods an extra electron shell is added:
E.g. Lithium has 3 electron in the configuration 2,1 H He Li Be B C N O F Ne Na Mg Al Si P S Cl Ar K Ca Fe Ni Cu Zn Br Kr Ag I Xe Pt Au Hg
Sodium has 11 electrons in the configuration 2,8,1
Potassium has 19 electrons in the configuration __,__,__,__

14. Fact 3: Most of the elements are metals:
The Periodic Table
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Fact 3: Most of the elements are metals:
These elements are metals H He Li Be B C N O F Ne Na Mg Al Si P S Cl Ar K Ca Fe Ni Cu Zn Br Kr Ag I Xe Pt Au Hg
These elements are non-metals
This line divides metals from non-metals

15. The Periodic Table
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Fact 4: (Most important) All of the elements in the same group have similar PROPERTIES. This is how I thought of the periodic table in the first place. This is called PERIODICITY. H He Li Be B C N O F Ne Na Mg Al Si P S Cl Ar K Ca Fe Ni Cu Zn Br Kr Ag I Xe Pt Au Hg
E.g. consider the group 1 metals. They all:
Are soft
Can be easily cut with a knife
React with water

16. Bonding
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Hi. My name’s Johnny Chlorine. I’m in Group 7, so I have 7 electrons in my outer shell Cl
I’d quite like to have a full outer shell. To do this I need to GAIN an electron. Who can help me?

17. Here comes my friend, Sophie Sodium
Bonding
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Here comes my friend, Sophie Sodium Na
Hey Johnny. I’m in Group 1 so I have one electron in my outer shell. I don’t like having just one electron so I’m quite happy to get rid of it. Do you want it?
Okay - + Cl Na
Now we’ve both got full outer shells and we’ve both gained a charge. We’ve formed an IONIC bond.

18. This is called an ion (in this case, a positive hydrogen ion)
Ions
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An ion is formed when an atom gains or loses electrons and becomes charged: + -
The electron is negatively charged
The proton is positively charged + +
If we “take away” the electron we’re left with just a positive charge:
This is called an ion (in this case, a positive hydrogen ion)

19. Ionic bonding Na Cl Na + Cl -
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This is where a metal bonds with a non-metal (usually). Instead of sharing the electrons one of the atoms “_____” one or more electrons to the other. For example, consider sodium and chlorine:
Sodium has 1 electron on its outer shell and chlorine has 7, so if sodium gives its electron to chlorine they both have a ___ outer shell and are ______.
A _______ charged sodium ion (cation)
A _________ charged chloride ion (anion)
As opposed to covalent bonds, ionic bonds form strong forces of attraction between different ions due to their opposite ______, causing GIANT IONIC STRUCTURES to form (e.g sodium chloride) with ______ melting and boiling points: Na Cl Na + Cl -

20. Some examples of binary salts
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Magnesium chloride: Cl Mg 2+ Mg + Cl - Cl
MgCl2
Calcium oxide: O Ca + 2+ 2-
CaO

21. Solution containing copper and chloride ions
Electrolysis
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++++
----
Positive electrode
Negative electrode
Cu2+
Cl-
Solution containing copper and chloride ions
Cu2+
Cl-
Cu2+
Cl-

22. Electrolysis
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Electrolysis is used to separate a metal from its compound.
= chloride ion
= copper ion
When we electrolysed copper chloride the _____ chloride ions moved to the ______ electrode and the ______ copper ions moved to the ______ electrode – OPPOSITES ATTRACT!!!

23. Electrolysis equations
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We need to be able to write “half equations” to show what happens during electrolysis (e.g. for copper chloride):
At the negative electrode the positive ions GAIN electrons to become neutral copper ATOMS. The half equation is:
Cu e Cu 2
At the positive electrode the negative ions LOSE electrons to become neutral chlorine MOLECULES. The half equation is:
Cl e Cl2 2 2

24. Purifying Copper ++++ ---- Impure copper Pure copper
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++++
----
Impure copper
Pure copper
Cu2+
Solution containing copper ions
At the positive electrode:
Cu(s) Cu2+(aq) + 2e-
At the negative electrode:
Cu2+(aq) + 2e Cu(s)

25. Electrolysis of Aluminium Oxide
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Overall:
Aluminium oxide aluminium + oxygen
2Al2O3(l) Al(l) O2(g)
At the cathode:
At the anode:
Al3+(l) + 3e Al(l)
2O2-(l) - 4e O2(g)

26. Properties of metals
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Metals have very high melting points (which means that they are usually _____) whereas non-metals will melt at lower ___________
All metals conduct heat and __________ very well, whereas non-metals don’t (usually)
Metals are strong and ______ but bendable. Non-metals are usually _____ or they will snap.
Metals will _____ when freshly cut or scratched, whereas non-metals are usually dull.
Metals have higher _______ than non-metals (i.e. they weigh more)
Metals can be used to make ______ (a mixture of different metals)
Words - alloys, electricity, solids, weak, densities, temperatures, tough, shine

27. Alloys
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Steel is an “alloy” – i.e. a mixture of metals. Here are other alloys:
Gold mixed with copper
Aluminium mixed with magnesium and copper
Aluminiun mixed with chromium