Unit 1: The Periodic Table UNIT 1: The Periodic Table Part 1: Trends in the periodic table The Periodic Table LO 1. Describe the Periodic Table as a method of classifying elements and its use to predict properties of elements. LO 2 Describe the change from metallic to non-metallic character across a Period LO 3Describe the relationship between Group number, number of valency electrons and metallic/non-metallic character. Complete the STARTER activity within your hand out. Start Timer 5 Minutes 5 4 3 2 1 0 Why is the Periodic Table important to me? • The periodic table is the most useful tool to a chemist. • You get to use it on every test. • It organizes lots of information about all the known elements. Pre-Periodic Table Chemistry … • …was a mess!!! • No organization of elements. • Imagine going to a grocery store with no organization!! • Difficult to find information. • Chemistry didn’t make sense. Dmitri Mendeleev: Father of the Table HOW HIS WORKED… • Put elements in rows by increasing atomic weight. • Put elements in columns by the way they reacted. SOME PROBLEMS… • He left blank spaces for what he said were undiscovered elements. (Turned out he was right!) • He broke the pattern of increasing atomic weight to keep similar reacting elements together. The Current Periodic Table • Mendeleev wasn’t too far off. • Now the elements are put in rows by ATOMIC NUMBER!! increasing • The horizontal rows are called periods and are labeled from 1 to 7. • The vertical columns are called groups are labeled from 1 to 18. Groups…Here’s Where the Periodic Table Gets Useful!! • Elements in the same group have similar chemical and physical properties!! • (Mendeleev did that on purpose.) Why?? • They have the same number of valence electrons. • They will form the same kinds of ions. Families on the Periodic Table • Columns are also grouped into families. • Families may be one column, or several columns put together. • Families have names rather than numbers. (Just like your family has a common last name.) Hydrogen • Hydrogen belongs to a family of its own. • Hydrogen is a diatomic, reactive gas. • Hydrogen was involved in the explosion of the Hindenberg. • Hydrogen is promising as an alternative fuel source for automobiles Alkali Metals • 1st column on the periodic table (Group 1) not including hydrogen. • Very reactive metals, always combined with something else in nature (like in salt). • Soft enough to cut with a butter knife Alkaline Earth Metals • Second column on the periodic table. (Group 2) • Reactive metals that are always combined with nonmetals in nature. • Several of these elements are important mineral nutrients (such as Mg and Ca Transition Metals • Less reactive harder metals • Includes metals used in jewelry and construction. • Metals used “as metal.” Group 3 • Elements in group 3 • Aluminum metal was once rare and expensive, not a “disposable metal.” Group 4 • Elements in group 4 • Contains elements important to life and computers. • Carbon is the basis for an entire branch of chemistry. • Silicon and Germanium are important semiconductors. Group 5 • Elements in group 5 • Nitrogen makes up over ¾ of the atmosphere. • Nitrogen and phosphorus are both important in living things. • Most of the world’s nitrogen is not available to living things. • The red stuff on the tip of matches is phosphorus. Group 6 • Elements in group 6 • Oxygen is necessary for respiration. • Many things that stink, contain sulfur (rotten eggs, garlic, skunks,etc.) Halogens • Elements in group 7 • Very reactive, volatile, diatomic, nonmetals • Always found combined with other element in nature . • Used as disinfectants and to strengthen teeth. The Noble Gases UNIT 1: The Periodic Table Part 2: Group 1 Lesson Objectives • Describe the properties and reactivity of lithium, sodium and potassium in Group 1 • Use the trends within the group to predict the properties of other elements. Group I Where are the alkali metals? The elements in group 1, on the left of the periodic table, are called the alkali metals. lithium Li sodium Na potassium K rubidium Rb caesium Cs francium Fr These metals are all very reactive and are rarely found in nature in their elemental form. Why are they called the ‘alkali metals’? The alkali metals are so reactive that, as elements, they have to be stored in oil. This stops them reacting with oxygen in the air. Alkali metals are soft enough to be cut with a knife, and the most common alkali metals, lithium, sodium and potassium, all float on water. The elements in group 1 also react with water and form alkaline compounds. This is why they are called alkali metals. What are the properties of the alkali metals? The characteristic properties of the alkali metals are: They are soft and can be cut by a knife. Softness increases going down the group. They have a low density. Lithium, sodium and potassium float on water. They have low melting and boiling points. These properties mean that the alkali metals are different to typical metals. However, alkali metals do also share some properties with typical metals: They are good conductors of heat and electricity. They are shiny. This is only seen when alkali metals are freshly cut. What are the trends in density? What is the trend in density? The alkali metals generally become more dense going down the group, but the trend is not perfect because potassium is less dense than sodium. Element Density (g/dm3) lithium 0.53 sodium 0.97 potassium 0.86 rubidium 1.53 caesium 1.87 Water has a density of 1g/dm3. Which elements in group 1 will float on water? What are the trends in melting point? What are the trends in boiling point? What is the trend in melting and boiling points? The melting points and boiling points of alkali metals decrease going down the group. Element Melting point (°C) Boiling point (°C) lithium 181 1342 sodium 98 883 potassium 64 760 rubidium caesium 39 28 686 671 The melting and boiling points decrease going down group 1 because the atoms get larger. Melting points are lower than for typical, transition, metals, because alkali metals only have 1 electron in their outer shell. Not much heat energy is needed for this electron to be lost. Trends in Chemical Reactivity Reactions all involve the loss of the outermost electron which changes the metal atom into a metal 1+ ion. Losing this electron seems to get easier as we go down the group. Li Na K Rb Cs Reactivity Increases Reactivity increases down the group. 1. The outer electron (-) gets further from the nucleus (+) as you go down the group. This reduces the force of attraction. 2. The inner shells ‘shield’ the outermost electron from the attraction from the nucleus. Both factors make it easier to lose the outer electron as you go down the group. Reactivity Increases Reactivity and Electron Structures Reaction with Water The Group 1 elements all react vigorously with water. Hydrogen gas is produced which sometimes catches fire. An alkali is left behind in the solution which is why these elements are often called ‘The Alkali Metals’. Reaction of Lithium Li H H Li O H H O O H + Li + Li H H - O H Reaction of Lithium with Water Lithium fizzes quickly in water forming lithium hydroxide and hydrogen. Lithium + water g Lithium hydroxide + hydrogen 2Li(s) + 2H2O(l) 2LiOH(aq) + H2(g) The solution that remains is strongly alkaline. Reaction of Sodium with Water Sodium fizzes very quickly in water. The gas given off can be ignited by a lighted splint. Sodium + water g Sodium hydroxide + hydrogen 2Na(s) + 2H2O(l) sodium on water 2NaOH(aq) + H2(g) enlarged Potassium with Water • Lithium fizzes. Sodium reacts more vigorously. • What will potassium do? What will the word equation and chemical equations be for the reaction of potassium with water? Potassium + water Potassium + water 2K(s) + 2H2O(l) Potassium hydroxide + hydrogen 2KOH(aq) + H2(g) The Group 1 Metals and oxygen The Group 1 elements burn in air to form metal oxides. Don’t try to put them out with water! Lithium + oxygen 4Li (s) + O2(g) Lithium Oxide 2 Li2O (s) What will the word equation and chemical equations be for the reaction of sodium with air? Sodium + oxygen sodium oxide 4 Na(s) + O2 (g) 2Na2O (s) The Group 1 Metals and chlorine The Group 1 elements burn in chlorine to form metal chlorides. Lithium + chlorine 2Li (s) + Cl2(g) 2 LiCl (s) Lithium chloride What will the word equation and chemical equations be for the reaction of sodium with chlorine? Sodium + chlorine 2 Na(s) + Cl2 (g) Sodium chloride 2NaCl (s) Uses of the Group 1 Metals The metals themselves are too reactive to have many uses although sodium vapour gives street lights their yellow glow. Lithium metal is used to improve the strength of aircraft alloys and is also used in some electrical batteries. Common sodium compounds include “salt”, (sodium chloride), “bicarbonate” (sodium hydrogen carbonate), washing soda (sodium carbonate) and caustic soda (sodium hydroxide.) Potassium compounds are used in “NPK fertilisers”, in weedkillers, explosives and many other chemicals. sodium light potassium UNIT 1: The Periodic Table Part 3: Reactivity Series Reactivity Series • There are lots of different metals on Earth and they all behave differently. • You may have tested properties of many metals. For example, strength and hardness. These are physical properties. • The chemical properties are also important. How fast they react with water or acid is a chemical property. Reactivity Series • Let us look at the 4 metals – copper, iron, magnesium and zinc. Reactivity Series • When each of these metals are added to hydrochloric acid (HCl) they react. Some react faster than others. • Let us now take a look at the reactions. Reactivity Series • Can you put the metals into the order of reactivity (with the most reactive first and the least reactive last)? • 1 – Magnesium (Mg) Most reactive • 2 – Zinc (Zn) • 3 – Iron (Fe) • 4 – Copper (Cu) Least reactive Metal Displacement Reactions • The metals displacement reaction can be quite confusing, so pay attention very carefully!!! • In this reaction we are going to react the four metals we have just looked at (Cu, Fe, Mg, Zn) with different solutions. • The solutions are: • • • • Copper sulphate Magnesium sulphate Iron sulphate Zinc sulphate Salt solutions Metal Displacement Reactions • A small piece of each metal is placed on a spotting tile as shown in the diagram above. • A few drops of each solution is added to each metals and observed carefully to see whether it reacts or not. Metal Displacement Reactions • If the metal reacts with the salt solution then we put a tick in the table and if it doesn’t, we put a cross. magnesium zinc iron copper x x x x magnesium sulphate x x x zinc sulphate x x iron Sulphate x copper Sulphate Metal Displacement Reactions • Let us take a look at the metals in each reaction. Metal Displacement Reactions • Look at the table carefully. Can you see a pattern? magnesium zinc iron copper x x x x magnesium sulphate x x x zinc sulphate x x iron Sulphate x copper Sulphate Metal Displacement Reactions • The first obvious pattern you will notice is that none of the metals react with the metal solution containing the same metal. • For example: • magnesium doesn’t react with magnesium sulphate • copper doesn’t react with copper sulphate • But there is another pattern. A little more difficult to see at first sight. Can you see it? Metal Displacement Reactions Magnesium + copper sulphate Reaction (metal) (metal in sulphate solution) Copper + magnesium sulphate No reaction (metal) (metal in sulphate solution) • • The first reaction takes place because the metal (red) is more reactive than the metal in the sulphate solution (green). So the more reactive metal can displace (‘kick out’) the less reactive metal. The second reaction doesn’t take place because the metal (red) is less reactive than the metal in the sulphate solution (green). So the less reactive metal cannot displace (‘kick out’) the more reactive metal. Metal Displacement Reactions • Let’s look at an analogy to help us understand. Mick Magnesium Carl Copper + magnesium (Mg) + copper sulphate (Cu) (SO4) Suzy Sulphate Metal Displacement Reaction • Magnesium + Copper sulphate magnesium sulphate + copper (Mick) (Carl) (Suzy) (Mick) (Suzy) (Carl) • Mick Magnesium is a big, strong character. • Carl Copper is a small weak character who is going out with Suzy Sulphate. • Because Mick Magnesium is bigger and stronger he can ‘beat up’ (displace) Carl Copper and take Suzy Sulphate away. • So you end up with Mick Magnesium going out with Suzy Sulphate and Carl Copper on his own. Metal Displacement Reaction • Copper + magnesium sulphate copper + magnesium sulphate (Carl) (Mick) (Suzy) (Carl) (Mick) (Suzy) Cu + MgSO Cu + MgSO 4 4 • Carl Copper who is a small and weak character cannot ‘beat up’ (displace) Mick Magnesium who is a big and strong character, to take away Suzy Sulphate. • So, no reaction takes place. It remains the same. Metal Displacement Reaction • Let us now relate this to the chemical reaction: • A reaction will only take place if the metal is more reactive than the metal in the sulphate solution. • N.B. • DO NOT SAY THAT THE METAL IS STRONGER. IT IS NOT. IT IS MORE REACTIVE! UNIT 1: The Periodic Table Part 5: Metal Extraction (Blast Furnace Starter- Without your notes write out the reactivity series of metals EXTRACTION OF METALS EXTRACTION OF METALS •Describe the ease in obtaining metals from their ores by relating the elements to the reactivity series. •Describe the essential reactions in the extraction of iron from haematite. •Describe the conversion of iron into steel. •Describe the idea of changing the properties of iron by the controlled use of additives to form steel alloys. •Name the uses of mild steel and stainless steel. GENERAL PRINCIPLES THEORY The method used to extract metals depends on the . . . What do you think chemists consider when deciding which method is best? • purity required • energy requirements • cost of the reducing agent • position of the metal in the reactivity series GENERAL PRINCIPLES REACTIVITY SERIES K Na Ca Mg Al C Zn Fe H Cu Ag • lists metals in descending reactivity • hydrogen and carbon are often added • the more reactive a metal the less likely it will be found in its pure, or native, state • consequently, it will be harder to convert it back to the metal. GENERAL PRINCIPLES METHODS - GENERAL Low in series Cu, Ag occur native or extracted by roasting an ore Middle of series Zn, Fe metals below carbon are extracted by reduction of the oxide with carbon or carbon monoxide High in series Na, Al reactive metals are extracted using electrolysis - an expensive method due to energy costs Variations can occur due to special properties of the metal. GENERAL PRINCIPLES OCCURRENCE • ores of some metals are very common (iron, aluminium) • others occur only in limited quantities in selected areas • high grade ores are cheaper to process because, ores need to be purified before being reduced to the metal IRON EXTRACTION OF IRON GENERAL PROCESS • occurs in the BLAST FURNACE • high temperature process • continuous • iron ores are REDUCED by carbon / carbon monoxide • is possible because iron is below carbon in the reactivity series EXTRACTION OF IRON RAW MATERIALS HAEMATITE - Fe2O3 a source of iron COKE fuel / reducing agent CHEAP AND PLENTIFUL LIMESTONE conversion of silica into slag (calcium silicate) – USED IN THE CONSTRUCTION INDUSTRY AIR source of oxygen for combustion THE BLAST FURNACE G IN THE BLAST FURNACE IRON ORE IS REDUCED TO IRON. A THE REACTION IS POSSIBLE BECAUSE CARBON IS ABOVE IRON IN THE REACTIVITY SERIES C D Click on the letters to see what is taking place B B E F THE BLAST FURNACE COKE, LIMESTONE AND IRON ORE ARE ADDED AT THE TOP A Now move the cursor away from the tower THE BLAST FURNACE HOT AIR IS BLOWN IN NEAR THE BOTTOM CARBON + OXYGEN C + O CARBON + HEAT DIOXIDE CO 2 OXYGEN IN THE2AIR REACTS WITH CARBON IN THE COKE. THE REACTION IS HIGHLY EXOTHERMIC AND GIVES OUT HEAT. B B Now move the cursor away from the tower THE BLAST FURNACE THE CARBON DIOXIDE PRODUCED REACTS WITH MORE CARBON TO PRODUCE CARBON MONOXIDE C CARBON + CARBON DIOXIDE C + CO2 CARBON MONOXIDE 2CO Now move the cursor away from the tower THE BLAST FURNACE THE CARBON MONOXIDE REDUCES THE IRON OXIDE CARBON + IRON MONOXIDE OXIDE 3CO + Fe2O3 CARBON + IRON DIOXIDE 3CO2 + 2Fe REDUCTION INVOLVES REMOVING OXYGEN D Now move the cursor away from the tower THE BLAST FURNACE SILICA IN THE IRON ORE IS REMOVED BY REACTING WITH LIME PRODUCED FROM THE THERMAL DECOMPOSITION OF LIMESTONE CALCIUM (SLAG) CaCO CaO SILICATE + CO2 3 IS PRODUCED CaO + SiO2 CaSiO 3 MOLTEN SLAG IS RUN OFF AND COOLED E Now move the cursor away from the tower THE BLAST FURNACE MOLTEN IRON RUNS TO THE BOTTOM OF THE FURNACE. IT IS TAKEN OUT (CAST) AT REGULAR INTERVALS CAST IRON - cheap and easily moulded - used for drainpipes, engine blocks F Now move the cursor away from the tower THE BLAST FURNACE HOT WASTE GASES ARE RECYCLED TO AVOID POLLUTION AND SAVE ENERGY CARBON MONOXIDE - POISONOUS SULPHUR DIOXIDE - ACIDIC RAIN CARBON DIOXIDE - GREENHOUSE GAS RECAP G SLAG PRODUCTION • silica (sand) is found with the iron ore • it is removed by reacting it with limestone • calcium silicate (SLAG) is produced • molten slag is run off and cooled • it is used for building blocks and road foundations SLAG PRODUCTION • silica (sand) is found with the iron ore • it is removed by reacting it with limestone • calcium silicate (SLAG) is produced • molten slag is run off and cooled • it is used for building blocks and road foundations EQUATIONS limestone decomposes on heating calcium oxide combines with silica overall CaCO3 —> CaO + CO2 CaO + SiO2 —> CaSiO3 CaCO3 + SiO2 —> CaSiO3 + CO2 WASTE GASES AND POLLUTION SULPHUR DIOXIDE • sulphur is found in the coke; sulphides occur in the iron ore • burning sulphur and sulphides produces sulphur dioxide S • sulphur dioxide gives rise to acid rain SO2 + H2O + O2 ——> SO2 ——> H2SO3 sulphurous acid CARBON DIOXIDE • burning fossil fuels increases the amount of this greenhouse gas LIMITATIONS OF CARBON REDUCTION Theoretically, several other important metals can be extracted this way but are not because they combine with the carbon to form a carbide e.g. Molybdenum, Titanium, Vanadium, Tungsten STEEL MAKING Iron produced in the blast furnace is very brittle due to the high amount of carbon it contains. In the Basic Oxygen Process, the excess carbon is burnt off in a converter and the correct amount of carbon added to make steel. Other metals (e.g. chromium) can be added to make specialist steels. Removal of impurities CaO + SiO2 ——> SILICA add calcium oxide CaSiO3 CARBON add oxygen C + O2 ——> PHOSPHORUS add oxygen 2P + 5O2 ——> P4O10 SULPHUR add magnesium Mg + S ——> MgS CO2 TYPES OF STEEL MILD easily pressed into shape LOW CARBON soft, easily shaped HIGH CARBON strong but brittle STAINLESS chains and pylons chisels, razor blades, saws hard, resistant to corrosion tools, sinks, cutlery (contains chromium and nickel) UNIT 1: The Periodic Table Part 6: Metal Extraction (Zinc) Lesson Objectives •Describe in outline, the extraction of zinc from zinc blende. •Name the uses of zinc for galvanising and for making brass. Consider zincs position in the periodic table….. Which method of extraction would you expect to be used? Where do we get zinc from? The main source of zinc is zinc sulphide or zinc blende. This is found in Australia, Canada, USA, Thailand Zinc Extraction (1) The zinc sulphide ore is roasted in air to give impure zinc oxide. Zinc Sulfide + Oxygen ==>Zinc Oxide + Sulphur Dioxide Can you write a balanced symbol equation for the above reaction? 2ZnS(s) + 3O2(g) ==> 2ZnO(s) + 2SO2(g) Zinc Extraction The impure zinc oxide can be treated in two ways to extract the zinc: (a) It is roasted in a smelting furnace with carbon (coke, reducing agent) and limestone (to remove the acidic impurities). The chemistry is similar to iron from a blast furnace. C(s) + O2(g) ==> CO2(g) (very exothermic oxidation, raises temperature considerably) C(s) + CO2(g) ==> 2CO(g) (C oxidised, CO2 reduced) ZnO(s) + CO(g) ==> Zn(l) + CO2(g) (zinc oxide reduced by CO, Zn undergoes O loss) or direct reduction by carbon: ZnO(s) + C(s) ==> Zn(l) + CO(g) (ZnO reduced, C oxidised) The carbon monoxide acts as the reducing agent i.e. it removes the oxygen from the oxide. Zinc Extraction The impure zinc is then fractionally distilled from the mixture of slag and other metals like lead and cadmium out of the top of the furnace in an atmosphere rich in carbon monoxide which stops any zinc from being oxidised back to zinc oxide. The zinc can be further purified by a 2nd fractional distillation or more likely by dissolving it in dilute sulphuric acid and purified electrolysis. (This is coverd later) Extraction of Zinc A- Mixture of Zinc and coke Added to furnace B-Molten Zinc removed C- Zinc condenses D- Hot air blown in Fractional Distillation • Fractional distillation is most commonly used to separate two liquids if the • boiling points are quite close. Pure samples of each liquid can usually be • obtained, unless the boiling points are too close. Part 7:THE TRANSITION METALS Lesson Objective • Name the uses of copper related to its properties; electrical wiring and in cooking utensils. • Describe the properties of transition elements The Transition elements • Transition means “an in between state” and the transition elements come in between Group 2 and Group 3. Gp 2 Gp 3 H He Transition Elements Li Be B C N O F Ne Na Mg Al Si P S Cl Ar Cr Mn Fe Co Ni Cu Zn Ga Ge As Se Br Kr K Ca Sc Rb Sr Y Ti V Zr Nb Mo Tc Ru Rh Pd Ag Cd Cs Ba La Hf Ta W Re Os Ir Fr Ra Ac Rf Db Sg Bh Hs Mt Pt Au Hg ? ? ? In Sn Sb Te I Xe Tl Pb Bi Po At Rn General Characteristics Transition Elements Often act as catalysts They have high melting points Less reactive than Group 1 or Group 2 metals They mostly form coloured compounds They have high density Transition metals are often referred to as ‘typical’ metals Properties – Density • Similarities are more noticeable than differences although there are still some broad patterns. • They are all dense (heavy) which is what we expect of metals. Sc Ti V Cr Mn Fe Co Ni Cu Zn 9 8 7 6 5 4 3 2 1 0 Density (g/cm-3) Sc Ti V Cr Mn Fe Co Ni Cu Zn Properties – Melting Point E.g. Melting points show no regular pattern – other than nearly all being high which is typical of metals. (Note zinc doesn’t fit very well on either density or melting point.) Sc Ti V Cr Mn Fe Co Ni 2000 1800 1600 1400 1200 1000 800 600 400 200 0 Melting Point ( C) Cu Zn Sc Ti V Cr Mn Fe Co Ni Cu Zn Properties – Reactivity • Again it is similarities that stand out rather than differences: they tend to react relatively slowly (e.g.) with air, water and acid. • The general trend is to reduced activity across the PeriodicTable but again the trend is far from perfect with zinc in particular being more reactive than you might expect. Sc Ti V Cr Mn Fe Co Ni Cu Zn General reduced reactivity Rusting: a slow but costly process! Properties – Catalysis • A catalyst is a substance that speeds up a chemical reaction without being used up. • Catalysts are hugely valuable in industry where they can save time and energy. • Many transition elements ( and their compounds) are catalysts. Ni Ti V Fe Used in oil hydrogenation Used in plastic manufacture Uses • The three most commonly known transition elements are iron or steel, copper and zinc. iron or steel General engineering metal copper Electrical and plumbing work zinc Galvanising steel to protect it Activity • Pair the metal up with its uses copper iron or steel zinc Activity • Pair the metal catalyst with the substance. Fe Ni Ti V Activity • Pair the statement about the transition elements with the words The **** elements fit between group 2 and 3. catalysts They tend to be very**** reactive Most are not especially *** coloured They are all typical**** similar They often form compounds that are **** transition They often speed up reactions by acting as **** metals Which is a true statement about most transition elements? A. B. C. D. They are non-metals. They are light (low density). They are strong. They are non-conductors. Which of these does copper NOT tend to be used for? A. B. C. D. Plumbing work. Electrical work Ornaments and jewellery Tools Transition elements can speed up other reactions without getting used up in the process. What do we call substances that do this? A. B. C. D. Capitalists Catalysts Catholics Catapults Transition elements often form coloured compounds. What colour compound does copper usually form? A.Blue B.Yellow C.Red D.Violet How would you describe the reactivity of transition elements within the Periodic Table? A.Always more reactive across periods (left to right). B.Generally less reactive across periods (left to right). C.No change in reactivity. D.Changes but no trends in reactivity.