Module: Chemistry 3

Next page Module: Chemistry 3 The Periodic Table

Next page The units in this module are: C3a – What are atoms like? C3b – How atoms combine – Ionic bonding C3c – Covalent bonding and the periodic table C3d – The Group 1 elements C3e – The group 7 elements C3f – Electrolysis C3g – Transition elements C3h – Metal structure and properties Click on the links to take to the topic you wish to revise.

Next page C3a - What are atoms like? Atomic structure PEN calculations Electron arrangements Isotopes Download podcast here Main menu

Next page What are atoms like? All substances are made of atoms Atoms have a nucleus in the centre of the atom. The nucleus contains protons and neutrons. Electrons orbit the nucleus in energy shells. Back to C3a Main menu

Next page PEN calculations Each element has a different number of protons, electrons and neutrons. We can calculate the number of protons by looking at the proton number We calculate the number of electrons by looking at the proton number as the charges need to be equal We calculate the number of neutrons by the mass number minus the proton number Back to C3a Main menu

1st shell can hold maximum of 2 electrons 2nd shell can hold maximum of 8 electrons 3rd shell can hold maximum of 8 electrons Next page Electron arrangements The electrons in an atom are arranged in energy shells Rules for filling shells Start filling from first shell The shell must be full before you move into the next shell Fill this shell before you move into the next one Back to C3a Main menu

Next page Isotopes Isotopes are elements which have the same number of protons and electrons but a different number of neutrons. For example, carbon has three isotopes C-12, C-14 and C-13 Protons = 6 Electrons = 6 Neutrons = 6 Protons = 6 Electrons = 6 Neutrons = 7 Protons = 6 Electrons = 6 Neutrons = 8 Back to C3a Main menu

Next page Ready to test your knowledge? Click here to take you to a quiz on “What are atoms like?” Main menu

Next page C3b - Ionic bonding Forming ions Ionic bonding Properties of ionic compounds Download podcast here Main menu

Next page Forming Ions Atoms are uncharged particles Ions are particles that have a charge Ions are formed by gaining or losing electrons. The sodium atom loses an electron so that it has a full outer shell. The ion has a charge of +1 Back to C3b Main menu

Chlorine needs to gain one electron Sodium needs to lose one electron Next page Ionic Bonding The sodium atom gives the electron to the chlorine atom Both particles become charged. The opposite charges attract to form a very strong ionic bond Back to C3b Main menu

Next page Properties of Ionic Compounds Ionic compounds form giant ionic lattices in which positive and negative ions are attracted to each other. Because this attraction is strong, ionic compounds have high melting points Ionic compounds do not conduct electricity when they are solid but they do when they are molten. This is because the ions are free to move about. Back to C3b Main menu

Next page Ready to test your knowledge? Click here to take you to a quiz on “Ionic Bonding” Main menu

Next page C3c - Covalent bonding Forming covalent molecules Properties of covalent molecules The periodic table Download podcast here Main menu

Next page Forming Covalent Molecules When there are two non-metals, they bond covalently. This means there are shared pairsof electrons Water Each atom has a full outer shell Carbon Dioxide There are two shared pairs of electrons. This makes a double bond. Back to C3c Main menu

Next page Properties of Covalent Molecules Molecules are kept together by forces of attraction called intermolecular forces. Covalent molecules have low melting points because these forces of attraction between the molecules are weak. Covalent molecules do not conduct electricity as there are no free electrons. Back to C3c Main menu

Next page The Periodic Table The columns are called groups. Elements in groups have similar properties The rows are called periods We can identify which group an element is in by the number of electrons in the outer shell. The number of shells that have been used tell us which period it is in. E.g. Na = 2, 8, 1 Number of electrons in outer shell is 1 = Group 1 Three shells have been used = Period 3 Back to C3c Main menu

Next page Ready to test your knowledge? Click here to take you to a quiz on “Covalent Bonding” Main menu

Next page C3d - Group 1 elements Physical properties and electron arrangements Alkali metals and water Flame tests Reactivity Download podcast here Main menu

Next page Physical Properties and Electron Arrangements All the group 1 elements have 1 electron in the outer shell The first three alkali metals are less dense than water and float. They also have low melting points Back to C3d Main menu

Next page Alkali Metals and Water Alkali metals fizz, float, dissolve to form a colourless solution. When you add universal indicator it turns purple, proving that an alkali is made. Alkali metals react with cold water to produce a hydroxide and hydrogen gas Sodium + Water  Sodium Hydroxide + Hydrogen 2 Na + 2H2O  2NaOH + H2 Back to C3d Main menu

Next page Flame Tests Alkali metals burn with distinctive flame colours Burning the compound of an alkali metal will show the flame colour Lithium = red Sodium = orange/yellow Potassium = purple Back to C3d Main menu

Next page Reactivity of Group 1 Elements The nucleus contains protons and neutrons, therefore it is positive overall. The electrons are held in orbit by an attractive force. To react, the atoms need to lose one electron to become a stable ion. The further this electron is from the positive nucleus, the easier it is to lose. Potassium is more reactive than lithium because the outer electron is further from the nucleus. This means it is easier to lose this electron so it reacts more vigorously. Back to C3d Main menu

Next page Ready to test your knowledge? Click here to take you to a quiz on “The Group 1 Elements” Main menu

Next page C3e - Group 7 elements Physical properties and electron arrangements Reactions with group 1 Trends Displacement Download podcast here Main menu

Next page Physical Properties and Electron Arrangements All the group 1 elements have 7 electron in the outer shell All give off coloured vapours – fluorine is yellow, chlorine is green, bromine is orange and iodine is purple. The state of matter changes from gas to liquid to solid because the melting point increases down the group Back to C3e Main menu

Next page Reactions with Group 1 Group 7 elements have 7 electrons in the outer shell and need to gain 1 electron to have a full outer shell. Group 1 elements have 1 electron in the outer shell and need to lose 1 electron to have a full outer shell. Group 7 and Group 1 elements react vigorously together to produce metal halides Lithium + Chlorine  Lithium Chloride 2 Li + Cl2  2 LiCl Back to C3e Main menu

Next page Trends As we go down the group the halogens become less reactive Fluorine is the most reactive and astatine is the least reactive As we move down the group the state of matter changes because the melting point increases The colour of the element becomes darker down the group Back to C3e Main menu

Next page Displacement Reactions A more reactive halogen will displace a less reactive halogen from an aqueous solution of its metal halide Chlorine will displace bromides and iodides Bromine will displace iodides Potassium bromide + Chlorine  Potassium Chloride + Bromine 2 KBr + Cl2  2 KCl + Br2 Back to C3e Main menu

Next page Ready to test your knowledge? Click here to take you to a quiz on “The Group 7 Elements” Main menu

Next page C3f - Electrolysis Key terms of electrolysis Electrolysis of sulphuric acid Electrolysis of aluminium oxide Download podcast here Main menu

Next page Key Terms of Electrolysis Electrolysis is the splitting up of an ionic compound by passing electricity through it An electrolyte is the liquid or solution that is being split up and conducts An ion is a charged particle Cathode is the negative electrode Anode is the positive electrode Back to C3f Main menu

Next page Electrolysis of Sulphuric Acid Sulphuric acid can be split up using electrolysis The hydrogen ions are attracted to the cathode and forms hydrogen gas 2 H+ + 2 e-  H2 Hydrogen burns with a squeaky pop The hydroxide ions are attracted to the anode and forms oxygen gas 4 OH- - 4 e-  O2 + 2 H2O Oxygen relights a glowing splint Back to C3f Main menu

Next page Electrolysis of Aluminium Oxide Aluminium can be extracted from its ore using electrolysis Aluminium oxide is dissolved in cryolite to lower the melting point When a current is passed through the liquid: Positive aluminium ions move towards the cathode and forms aluminium Al3+ + 3e-  Al Negative oxide ions move towards the anode and forms oxygen gas 2 O2- - 4e-  O2 Back to C3f Main menu

Next page Ready to test your knowledge? Click here to take you to a quiz on “Electrolysis” Main menu

Next page C3g - Transition Elements General properties and special properties Thermal decomposition Precipitation reactions Download podcast here Main menu

Next page General Properties and Special Properties The transition metals are a group of elements in the centre of the periodic table Transition metals have the general properties of metals e.g. shiny, good conductor etc Special properties of transition metals are that their compounds are often coloured Copper, Cu2+ blue Iron, Fe2+ grey green Iron, Fe3+  orange brown Transition metals also make good catalysts Iron in the Haber process Nickel in manufacturing margarine Back to C3g Main menu

Next page Thermal Decomposition Transition metal carbonates decompose on heating A colour change occurs and a metal oxide and carbon dioxide gas is formed. Copper Carbonate  Copper Oxide + Carbon Dioxide CuCO3 CuO + CO2 Back to C3g Main menu

Next page Precipitation Reactions A precipitate is an insoluble solid Precipitates sometimes form when sodium hydroxide is added to a solution containing a transition metal ion. Some transition metal ions form distinctive coloured precipitates Copper, Cu2+ blue Iron, Fe2+ grey green Iron, Fe3+  orange brown Back to C3g Main menu

Next page Ready to test your knowledge? Click here to take you to a quiz on “Transition Elements” Main menu

Next page C3h - Metal Structures and Properties Properties and uses Metallic bonding Superconductors Download podcast here Main menu

Next page Properties and Uses Metals are useful because of their properties Metals are Lustrous (shiny) e.g. gold in jewellery High density e.g. steel in drill bits High melting and boiling points e.g. tungsten in filaments Good conductors e.g. copper in wiring Back to C3h Main menu

Next page Metallic Bonding Metal atoms are packed very close in a regular arrangement held together by metallic bonds. The structure can be described as closely packed metal ions in a ‘sea’ of delocalised electrons. Because the electrons are free to move around it allows the metal to conduct. The metal is held together by a strong force of attraction between the metal ions and the electrons. This is why they have high melting points. Back to C3h Main menu

Next page Superconductors Metals are able to conduct electricity At very low temperatures some metals can become superconductors. A superconductor has very little resistance so no energy is lost Superconductors can be used in powerful electromagnets and very fast electronic circuits. Back to C3h Main menu

Next page Ready to test your knowledge? Click here to take you to a quiz on “Metal Structures” Main menu

Module: Chemistry 3