If a helium atom was the size of a full stop, then the average gerbil would be the size of the Earth. Atoms: very small

Now let’s pretend that the helium atom on the right is the size of the Earth. What’s wrong with this simple picture? Atoms: very small

The helium atom is not in the right proportions. The three subatomic particles are wrongly enormous in comparison to the atom’s radius. If it was the size of the Earth, then the nucleus would be about size of IVC (at the centre of the Earth). How big is a nucleus?

C4 revision

A* ions Can you work out the charge on an ion from its chemical formula? What is the formula of Calcium chloride Lithium oxide Aluminium bromide

Subatomic particle Relative charge Relative mass Common depiction Proton+11 Neutron01 Electron 1  Subatomic particles in more detail

Columns of elements H Li Na K Rb Cs Fr Be Mg Ca Sr Ba Ra Ga In Tl Al B Ge Sn Pb Si C Sb Bi P N AsSe Te Po O S He Kr Ne Ar Rn Xe ScTiVCrMnFeCoNiCuZn YZrNbMoTcRuPdAgCdRh HfTaWReOsIrAuHgLaPt RfDbSgBhHsMt??Ac? Br At Cl F I What are columns of elements called? Groups 10 Group number transition metals

Rows of elements H He LiBeNOFNeBC NaMgAlPSClArSi KScTiVCrMnFeCoNiCuZnGaGeSeBrCaKrAs RbYZrNbMoTcRuPdAgCdInSnSbSrTeRhIXe CsBaHfTaWReOsIrAuHgTlPbBiPoLaAtPtRn FrRaRfDbSgBhHsMt??Ac? Periods What are rows of elements called? Period number Going across a period, the atomic number (number of protons) increases by 1 with every element. For example, phosphorus has the atomic number 15. What is the atomic number of scandium?

Li 7 3 (No. of protons) No. of protons + neutrons Lithium Number of protons Number of electrons = Atomic number does not always equal the number of neutrons. Lithium Electrons3 Protons3 Neutrons4 Mass number Atomic number or proton number

Two important groups H Li Na K Rb Cs Fr Be Mg Ca Sr Ba Ra Ga In Tl Al B Ge Sn Pb Si C Sb Bi P N AsSe Te Po O S He Kr Ne Ar Rn Xe ScTiVCrMnFeCoNiCuZn YZrNbMoTcRuPdAgCdRh HfTaWReOsIrAuHgLaPt RfDbSgBhHsMt??Ac? Br At Cl F I 71 Alkali metalsHalogens

Electronic Structure All the Group 1 elements have 1 electron in the outermost shell. Li Na K Rb Cs Lithium Sodium Potassium Rubidium Caesium 2,8,1 2,8,8,1 2,1

Trends in Density Lithium, sodium and potassium are all less dense than water and so will float. Densities follow a general, although not perfect, trend. ElementSymbolDensity LithiumLi0.53 SodiumNa0.97 PotassiumK0.86 RubidiumRb1.53 CaesiumCs1.88

Melting Points The atoms in the Group 1 elements are bonded together using just one outer shell electron per atom. As a result, melting points are low compared to most metals. ElementMelt. Point (C) Lithium181 Sodium98 Potassium Rubidium39 Caesium Can you predict the missing data? 63 29

The Halogens

Electronic Structure All the Group 7 elements have 7 electrons in the outermost shell. F Cl Br I At Bromine Iodine Astatine Fluorine 2,7 Chlorine 2,8,7 And so on

Halogen molecules All the Group 7 elements are molecules containing two atoms. Each atom is 1 electron short of full outer shell. By sharing electrons, full outer electron shells are achieved. F F F F F atom F 2 molecule Q: Hydrogen is not a halogen, but it could be. Explain why and draw a hydrogen molecule.

The group 7 elements get darker as you go down the group. They also get denser. F Cl Br I Darker & Denser Bromine solution. Note the bromine vapour above the liquid The Halogens

Patterns: physical state Melting Points and boiling points increase as the molecules get bigger. What is the physical state: solid, liquid or gas? ElementSize Melting Point ( o C) Boiling Point ( o C) Physical State Fluorine Chlorine Bromine -759 Iodine gas liquid solid

Fill in the table SpeciesName ProtonsNeutronsElectrons Electron configuration KPotassium19202,8,8,1 Ca Oxygen ion8 Mg ion in magnesium chloride Fluoride ion Na lithium ion in lithium oxide Halogen ion in LiCl 2+ +

Fill in the table SpeciesName ProtonsNeutronsElectrons Electron configuration KPotassium19202,8,8,1 Ca Oxygen ion8 Mg ion in magnesium chloride Fluoride ion Na lithium ion in lithium oxide Halogen ion in LiCl 2+ +

Fill in the table SpeciesName ProtonsNeutronsElectrons Electron configuration KPotassium ,8,8,1 CaCalcium ion20 182,8,8 OOxygen ion88102,8 Mg Mg ion in magnesium chloride ,8 FFluoride ion910 2,8 NaSodium ion ,8 Li lithium ion in lithium oxide 3422 Cl Halogen ion in LiCl ,8,

Working out ionic formulae For each pair of atoms, work out the formula of their compound. 1.Mg and FMg  Mg 2+ F  F - Formula = MgF 2 2.Ca and SFormula = 3.Li and OFormula = 4.Be and IFormula = 5.Al and OFormula = 6.Al and ClFormula = 7.Rb and Br Formula = 8.K and S Formula =

Working out ionic formulae For each pair of atoms, work out the formula of their compound. 1.Mg and FMg  Mg 2+ F  F - Formula = MgF 2 2.Ca and SCa  Ca 2+ S  S 2- Formula = CaS 3.Li and OLi  Li + O  O 2- Formula = Li 2 O 4.Be and IBe  Be 2+ I  I - Formula = BeI 2 5.Al and OAl  Al 3+ O  O 2- Formula = Al 2 O 3 6.Al and ClAl  Al 3+ Cl  Cl - Formula = AlCl 3 7.Rb and Br Rb  Rb + Br  Br - Formula = RbBr 8.K and S K  K + S  S 2- Formula = K 2 S

Astatine comes below iodine in Group 7 What might its melting point be (in o C)? A. – 225 B. +82 C D. +300