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

The structure of the atom 19/09/2018 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”)

Mass and atomic number 4 He 2 19/09/2018 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)

How many protons, neutrons and electrons? Mass and atomic number 19/09/2018 How many protons, neutrons and electrons? 1 11 16 H B O 1 5 8 23 35 238 Na Cl U 11 17 92

Isotopes 19/09/2018 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.

Relative Atomic Mass 19/09/2018 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 35 + 1 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?

Electron structure 39 K 19 Consider an atom of Potassium: 19/09/2018 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

Trends in Group 1 Consider a sodium atom: + 19/09/2018 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

Trends in Group 7 Consider a flourine atom: - 19/09/2018 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

Periodic Table Introduction 19/09/2018 Periodic Table Introduction

Horizontal rows are called PERIODS Periodic table 19/09/2018 Mendeleev The periodic table arranges all the elements in groups according to their properties. Vertical columns are called GROUPS Horizontal rows are called PERIODS

The Periodic Table 19/09/2018 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

The Periodic Table 19/09/2018 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 __,__,__,__

Fact 3: Most of the elements are metals: The Periodic Table 19/09/2018 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

The Periodic Table 19/09/2018 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

Bonding 19/09/2018 Cl 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?

Here comes my friend, Sophie Sodium Bonding 19/09/2018 Cl 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.

This is called an ion (in this case, a positive hydrogen ion) Ions 19/09/2018 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)

Ionic bonding Na Cl Na + Cl - 19/09/2018 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 -

Some examples of binary salts 19/09/2018 Cl - Magnesium chloride: Cl Mg 2+ Mg + Cl - Cl MgCl2 Calcium oxide: O Ca + 2+ 2- CaO

Solution containing copper and chloride ions Electrolysis 19/09/2018 ++++ ---- Positive electrode Negative electrode Cu2+ Cl- Solution containing copper and chloride ions Cu2+ Cl- Cu2+ Cl-

Electrolysis 19/09/2018 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!!!

Electrolysis equations 19/09/2018 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: Cu2+ + 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

Purifying Copper ++++ ---- Impure copper Pure copper 19/09/2018 ++++ ---- 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)

Electrolysis of Aluminium Oxide 19/09/2018 Overall: Aluminium oxide aluminium + oxygen 2Al2O3(l) 4Al(l) + 3O2(g) At the cathode: At the anode: Al3+(l) + 3e- Al(l) 2O2-(l) - 4e- O2(g)

Properties of metals 19/09/2018 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

Alloys 19/09/2018 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