2 UNIT 1: The Periodic Table Part 1: Trends in the periodic table
3 The Periodic TableLO 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 PeriodLO 3Describe the relationship between Group number, number of valency electrons and metallic/non-metallic character.
4 Complete the STARTER activity within your hand out. Start Timer 5 Minutes54321
5 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.
6 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.
7 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.
8 The Current Periodic Table Mendeleev wasn’t too far off.Now the elements are put in rows by increasing ATOMIC NUMBER!!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.
9 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.
10 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.)
11 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
12 Alkali Metals1st 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
13 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
14 Transition Metals Less reactive harder metals Includes metals used in jewelry and construction.Metals used “as metal.”
15 Group 3 Elements in group 3 Aluminum metal was once rare and expensive, not a “disposable metal.”
16 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.
17 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.
18 Group 6 Elements in group 6 Oxygen is necessary for respiration. Many things that stink, contain sulfur (rotten eggs, garlic, skunks,etc.)
19 Halogens Elements in group 7 Very reactive, volatile, diatomic, nonmetalsAlways found combined with other element in nature .Used as disinfectants and to strengthen teeth.
25 Where are the alkali metals? The elements in group 1, on the left of the periodic table, are called the alkali metals.FrCsRbKNaLilithiumsodiumpotassiumrubidiumcaesiumfranciumThese metals are all very reactive and are rarely found in nature in their elemental form.
26 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.Photo credit: Dr John MilehamThe elements in group 1 also react with water and form alkaline compounds. This is why they are called alkali metals.
27 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:Photo credit: Dr John MilehamImage is of sodium, freshly cut. Sodium tarnishes very quickly – within approximately 20 seconds. In this image, you can see how it is already tarnishing, starting from the right hand side.They are good conductors of heat and electricity.They are shiny. This is only seen when alkali metals are freshly cut.
28 What are the trends in density? Teacher notesThis animated graph could be used as a stimulus for either small-group or whole-class discussion on trend in density among the alkali metals.
29 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.ElementDensity (g/dm3)lithium0.53sodium0.97potassium0.86rubidium1.53caesium1.87Water has a density of 1 g/dm3.Which elements in group 1 will float on water?
30 What are the trends in melting point? Teacher notesThis animated graph could be used as a stimulus for either small-group or whole-class discussion on the melting points among the alkali metals.
31 What are the trends in boiling point? Teacher notesThis animated graph could be used as a stimulus for either small-group or whole-class discussion on the boiling points among the alkali metals.
32 What is the trend in melting and boiling points? The melting points and boiling points of alkali metals decrease going down the group.ElementMelting point (°C)Boiling point (°C)lithium1811342sodium98883potassium64760rubidium39686The size of atom increases down Group I and therefore attraction between positive nucleus and the delocalised electrons is weaker (electrons are further away from the nucleus and therefore less heat energy is required in order for the atom to lose its outer electron)caesium28671The 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.
33 Trends in Chemical Reactivity Reactivity increases down the group.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.LiNaKRbCsReactivity Increases
34 Reactivity and Electron Structures 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
35 Reaction with WaterThe 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 LithiumLiHOHO-Li+H
36 Reaction of Lithium with Water Lithium fizzes quickly in water forming lithium hydroxide and hydrogen.Lithium + water g Lithium hydroxide + hydrogen2Li(s) + 2H2O(l) 2LiOH(aq) + H2(g)The solution that remains is strongly alkaline.
37 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 + hydrogen2Na(s) + 2H2O(l) 2NaOH(aq) + H2(g)sodium on waterenlarged
38 2KOH(aq) + H2(g) 2K(s) + 2H2O(l) 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 + waterPotassium + water Potassium hydroxide + hydrogen2KOH(aq) + H2(g)2K(s) + 2H2O(l)
39 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 Lithium Oxide4Li (s) + O2(g) 2 Li2O (s)What will the word equation and chemical equations be for the reaction of sodium with air?Sodium + oxygen sodium oxide2Na2O (s)Na(s) + O2 (g) 4
40 The Group 1 Metals and chlorine The Group 1 elements burn in chlorine to form metal chlorides.Lithium + chlorine Lithium chloride2Li (s) + Cl2(g) 2 LiCl (s)What will the word equation and chemical equations be for the reaction of sodium with chlorine?Sodium + chlorine Sodium chloride2NaCl (s)Na(s) + Cl2 (g) 2
41 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 lightpotassium
42 UNIT 1: The Periodic Table Part 3: Reactivity Series
43 Reactivity SeriesThere 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.
44 Reactivity SeriesLet us look at the 4 metals – copper, iron, magnesium and zinc.
45 Reactivity SeriesWhen 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.
46 Reactivity SeriesCan you put the metals into the order of reactivity (with the most reactive first and the least reactive last)?1 – Magnesium (Mg)2 – Zinc (Zn)3 – Iron (Fe)4 – Copper (Cu)Most reactiveLeast reactive
47 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 sulphateMagnesium sulphateIron sulphateZinc sulphateSalt solutions
48 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.
49 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.magnesiumzincironcopperxsulphateSulphate
50 Metal Displacement Reactions Let us take a look at the metals in each reaction.
51 Metal Displacement Reactions Look at the table carefully. Can you see a pattern?magnesiumzincironcopperxsulphateSulphate
52 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 sulphatecopper doesn’t react with copper sulphateBut there is another pattern. A little more difficult to see at first sight. Can you see it?
53 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.
54 Metal Displacement Reactions Let’s look at an analogy to help us understand.Mick MagnesiumCarl CopperSuzy Sulphate+magnesium copper sulphate(Mg) (Cu) (SO4)
55 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.
56 Metal Displacement Reaction Copper + magnesium sulphate copper + magnesium sulphate(Carl) (Mick) (Suzy) (Carl) (Mick) (Suzy)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.Cu MgSO Cu MgSO4
57 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!
58 Part 4- Using Reactivity Series----- All in student notes... No ppt
59 UNIT 1: The Periodic Table Part 5: Metal Extraction (Blast Furnace
60 Starter- Without your notes write out the reactivity series of metals
62 EXTRACTION OF METALSDescribe 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.
63 GENERAL PRINCIPLESTHEORYThe 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
64 GENERAL PRINCIPLES • lists metals in descending reactivity REACTIVITY SERIESK 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 inits pure, or native, state• consequently, it will be harder to convert it back to the metal.
65 GENERAL PRINCIPLES Low in series occur native or METHODS - GENERALLow in series occur native orCu, Ag extracted by roasting an oreMiddle of series metals below carbon are extracted by reductionZn, Fe of the oxide with carbon or carbon monoxideHigh in series reactive metals are extracted using electrolysisNa, Al - an expensive method due to energy costsVariations can occur due to special properties of the metal.
66 GENERAL PRINCIPLESOCCURRENCE• 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
68 EXTRACTION OF IRON • occurs in the BLAST FURNACE 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
69 RAW MATERIALS EXTRACTION OF IRON HAEMATITE - Fe2O3 a source of iron COKE fuel / reducing agentCHEAP AND PLENTIFULLIMESTONE conversion of silica into slag(calcium silicate) – USED IN THECONSTRUCTION INDUSTRYAIR source of oxygen for combustion
70 THE BLAST FURNACEGIN THE BLAST FURNACE IRON ORE IS REDUCED TO IRON.THE REACTION IS POSSIBLE BECAUSE CARBON IS ABOVE IRON IN THE REACTIVITY SERIESClick on the letters to see what is taking placeACDBBEF
71 COKE, LIMESTONE AND IRON ORE ARE ADDED AT THE TOP THE BLAST FURNACECOKE, LIMESTONE AND IRON ORE ARE ADDED AT THE TOPNow move the cursor away from the towerA
72 HOT AIR IS BLOWN IN NEAR THE BOTTOM THE BLAST FURNACEHOT AIR IS BLOWN IN NEAR THE BOTTOMOXYGEN IN THE AIR REACTS WITH CARBON IN THE COKE. THE REACTION IS HIGHLY EXOTHERMIC AND GIVES OUT HEAT.CARBON + OXYGEN CARBON + HEATDIOXIDEC O CO2BBNow move the cursor away from the tower
73 C C + CO2 2CO THE BLAST FURNACE THE CARBON DIOXIDE PRODUCED REACTS WITH MORE CARBON TO PRODUCE CARBON MONOXIDECNow move the cursor away from the towerCARBON CARBON CARBONDIOXIDE MONOXIDEC + CO CO
74 D REDUCTION INVOLVES REMOVING OXYGEN THE BLAST FURNACE THE CARBON MONOXIDE REDUCES THE IRON OXIDECARBON IRON CARBON + IRONMONOXIDE OXIDE DIOXIDE3CO + Fe2O CO FeDNow move the cursor away from the towerREDUCTION INVOLVES REMOVING OXYGEN
75 CALCIUM SILICATE (SLAG) IS PRODUCED MOLTEN SLAG IS RUN OFF AND COOLED THE BLAST FURNACESILICA IN THE IRON ORE IS REMOVED BY REACTING WITH LIME PRODUCED FROM THE THERMAL DECOMPOSITION OF LIMESTONECALCIUM SILICATE (SLAG) IS PRODUCEDMOLTEN SLAG IS RUN OFF AND COOLEDCaCO3 CaO + CO2CaO + SiO CaSiO3ENow move the cursor away from the tower
76 F CAST IRON - cheap and easily moulded THE BLAST FURNACEMOLTEN IRON RUNS TO THE BOTTOM OF THE FURNACE.IT IS TAKEN OUT (CAST) AT REGULAR INTERVALSCAST IRON- cheap and easily moulded- used for drainpipes, engine blocksFNow move the cursor away from the tower
77 HOT WASTE GASES ARE RECYCLED TO AVOID POLLUTION AND SAVE ENERGY THE BLAST FURNACEGHOT WASTE GASES ARE RECYCLED TO AVOID POLLUTION AND SAVE ENERGYCARBON MONOXIDE - POISONOUSSULPHUR DIOXIDE - ACIDIC RAINCARBON DIOXIDE - GREENHOUSE GASRECAP
78 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
79 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 foundationsEQUATIONSlimestone decomposes on heating CaCO3 —> CaO CO2calcium oxide combines with silica CaO SiO2 —> CaSiO3overall CaCO SiO2 —> CaSiO3 + CO2
80 WASTE GASES AND POLLUTION SULPHUR DIOXIDE• sulphur is found in the coke; sulphides occur in the iron ore• burning sulphur and sulphides S O2 ——> SO2produces sulphur dioxide• sulphur dioxide gives SO H2O ——> H2SO3rise to acid rain sulphurous acidCARBON DIOXIDE• burning fossil fuels increases the amount of this greenhouse gas
81 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 carbidee.g. Molybdenum, Titanium, Vanadium, Tungsten
82 STEEL MAKINGIron 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 impuritiesSILICA add calcium oxide CaO SiO2 ——> CaSiO3CARBON add oxygen C O2 ——> CO2PHOSPHORUS add oxygen P O2 ——> P4O10SULPHUR add magnesium Mg S ——> MgS
83 TYPES OF STEELMILD easily pressed into shape chains and pylonsLOW CARBON soft, easily shapedHIGH CARBON strong but brittle chisels, razor blades, sawsSTAINLESS hard, resistant to corrosion tools, sinks, cutlery(contains chromium and nickel)
84 UNIT 1: The Periodic Table Part 6: Metal Extraction (Zinc)
85 Lesson ObjectivesDescribe in outline, the extraction of zinc from zinc blende.Name the uses of zinc for galvanising and for making brass.
86 Consider zincs position in the periodic table….. Which method of extraction would you expect to be used?
87 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
89 Zinc Extraction 2ZnS(s) + 3O2(g) ==> 2ZnO(s) + 2SO2(g) The zinc sulphide ore is roasted in air to give impure zinc oxide.Zinc Sulfide + Oxygen ==>Zinc Oxide + Sulphur DioxideCan you write a balanced symbol equation for the above reaction?2ZnS(s) + 3O2(g) ==> 2ZnO(s) + 2SO2(g)
90 Zinc ExtractionThe 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.
91 Zinc ExtractionThe 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)
92 Extraction of Zinc A- Mixture of Zinc and coke Added to furnace B-Molten Zinc removedC- Zinc condensesD- Hot air blown in
93 Fractional Distillation Fractional distillation is most commonly used to separate two liquids if theboiling points are quite close. Pure samples of each liquid can usually beobtained, unless the boiling points are too close.
96 Lesson ObjectiveName the uses of copper related to its properties; electrical wiring and in cooking utensils.Describe the properties of transition elements
97 The Transition elements Transition means “an in between state” and the transition elements come in between Group 2 and Group 3.Gp 2Gp 3HLiNaKRbCsFrBeMgGaGeSeBrCaKrInSnSbSrTeBaTlPbBiPoAtRaAlPNOSClFNeArRnISiXeHeBCAsTransition ElementsScTiVCrMnFeCoNiCuZnYZrNbMoTcRuPdAgCdRhHfTaWReOsIrAuHgLaPtRfDbSgBhHsMt?Ac
98 General Characteristics TransitionElementsOften act as catalystsLess reactivethan Group 1 orGroup 2 metalsThey mostly formcolouredcompoundsThey havehigh meltingpointsThey havehigh densityTransition metalsare often referred toas ‘typical’ metals
99 Properties – DensitySimilarities are more noticeable than differences although there are still some broad patterns.They are all dense (heavy) which is what we expect of metals.ScTiVCrMnFeCoNiCuZn
100 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.)ScTiVCrMnFeCoNiCuZn
101 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.Rusting: a slow but costly process!ScTiVCrMnFeCoNiCuZnGeneral reduced reactivity
102 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.VNiUsed in oil hydrogenationTiUsed in plastic manufactureFe
103 UsesThe three most commonly known transition elements are iron or steel, copper and zinc.iron or steelGeneral engineering metalcopperElectrical and plumbing workzincGalvanising steel to protect it
104 Pair the metal up with its uses ActivityPair the metal up with its usesiron or steelcopperzinc
105 Pair the metal catalyst with the substance. ActivityPair the metal catalyst with the substance.VTiFeNi
106 Pair the statement about the transition elements with the words ActivityPair the statement about the transition elements with the wordsThe **** elements fit between group 2 and 3.catalystsThey tend to be very****reactiveMost are not especially ***colouredThey are all typical****similarThey often form compounds that are ****transitionThey often speed up reactions by acting as ****metals
107 Which is a true statement about most transition elements?They are non-metals.They are light (low density).They are strong.They are non-conductors.
108 Which of these does copper NOT tend to be used for?Plumbing work.Electrical workOrnaments and jewelleryTools
109 Transition elements can speed up other reactions without getting used up in the process. What do we call substances that do this?CapitalistsCatalystsCatholicsCatapults
110 Transition elements often form coloured compounds Transition elements often form coloured compounds. What colour compound does copper usually form?BlueYellowRedViolet
111 How would you describe the reactivity of transition elements within the Periodic Table? Always more reactive across periods (left to right).Generally less reactive across periods (left to right).No change in reactivity.Changes but no trends in reactivity.