Chemical Families
Chemical FamiliesElements in the same Group have the same number of outershell electrons. The same number of outer shell electronsmeans similar chemical properties – so each Group is achemical family.Group 0 – The Noble Gases
Group 1 - Physical propertiesGroup 1 metals are unusual metals - some oftheir physical properties are different to typicalmetals.What properties unusual for metals are beingillustrated here?
ûüûûüü(only whenfreshly cut)ü? Group 1 metals are soft – can be cut with a knife They become dull soon after being cut, as they react withoxygen in the air rapidly to form alkali metal oxides They have low density – lithium, sodium and potassiumfloat on water They have low melting points – sodium and potassium meltfrom the heat generated when reacting with water
They also show trends in their physical properties:Going down Group 1 the metals:- get more soft- get more dense- melting at a lower temperatureBased on observing the physicalproperties of lithium, sodium andpotassium, we should be able topredict the physical properties ofrubidium and caesium:- very soft- more dense than potassium, may not float on water- easily melted (caesium melts just above room temp.)
Group 1 - Chemical PropertiesGroup 1 metals are very reactive.They are normally stored under oil. The oil acts as abarrier, preventing them from reacting with oxygen in theair, or with water.Reaction with oxygen (air)Group 1 metals all react with oxygen toproduce metal oxides when they arecut. The silvery surface becomes dull.The rate at which this happens allowsus to compare their reactivity.e.g. Na(s) O2(g) à Na2O(s)sodium oxygen sodium oxideBalance this chemical equation.
Reaction with waterGroup 1 metals all react with water to produce alkalinesolutions of metal hydroxides (this is why they are calledalkali metals). They all fizz, producing hydrogen gas. Forthese reasons we can consider Group 1 a chemical family.Li, Na and K float and move around on the surface of thewater while reacting, until they are completely dissolved. Itis an exothermic reaction – enough to melt sodium orpotassium!Observing the rate of this reaction allows us to comparetheir reactivity.e.g. Na(s) H2O(l) àNaOH(aq) H2(g)sodium water sodium hydroxide hydrogenBalance this chemical equation.
Trends in their chemical properties:more reactiveWe find that sodium is more reactive than lithium, andpotassium is more reactive than sodium.We can makepredictions about thereactivity of rubidiumand caesium: theirreactions with waterwill be extremelyviolent.
Group 1 elements react by losingtheir outer shell electron to formmetal ions with a 1 charge, whichhave a full outer shell.The further away from thepositively charged nucleus theouter shell electron is, the easierit is for the atom to lose it, sothe more reactive the element is.increasing reactivitySeparate SciencesExplaining the order of reactivity in Group 1[2,1][2,8,1]This is because the attractionbetween the negatively chargedelectron and the nucleus getsweaker the further away theelectron is.[2,8,8,1]
Group 7 - The HalogensFThe Halogens are the elements in Group 7They are non-metals, having coloured vapours.ClThe halogens consist of molecules made up ofpairs of atoms e.g. chlorine is Cl2(g)They also show trends in their physical andchemical properties, because they are achemical family.
Group 7 – Physical PropertiesGoing down the group: Fluorine is a very pale yellow gas Chlorine is a pale green gas Bromine is a red-orange liquid, producing an orangevapour readily Iodine is a grey solid, producing a purple vapour whenwarmedWhat trends is physical properties are described here?What would you predict the physical properties ofAstatine to be ?Hands upeveryone with acoloured vapour
Group 7 - Chemical propertiesThe halogens are also very reactive.With 7 electrons in their outer shell, they react by gainingan electron to complete their outer shell, or by sharingelectrons with other atoms.When a halogen atom reacts with a metal it gains anelectron and forms an ion with a 1- charge, which we call ahalide ion:fluoridechloridebromideiodideFClBrI-
Group 1 metals react with Group 7 non-metals to make saltscalled metal halides.For example, sodium metal react with chlorine gas to makesodium chloride.Re-write this word equation as a balanced chemical equation:sodium chlorine sodium chloride
Halogens can also react with other non-metals, sharingtheir outer shell electrons to form covalent bonds.hydrogen chlorine à hydrogen chlorideStart this movie at about 46s in.Re-write this word equation as a balanced chemical equation
Trend in Group 7 reactivityWe can use displacement reactions to determine the orderof reactivity of chlorine, bromine and iodine.A more reactive halogen can displace a less reactivehalogen from a solution of its halide salt.displaces chlorine displaces bromine displaces iodinefrom chloridefrom bromidefrom iodidesolutions ?solutions ?solutions ?YESchlorinebromineNOiodineNOYESYESNO
Reacting chlorine with: potassium chloride solution potassium bromide solution potassium iodide solutionReacting bromine with: potassium chloride solution potassium bromide solution potassium iodide solutionWhat will we see? Why?What will we see? Why?
chlorine bromide ions à bromine chloride ions2Br-(aq)Cl2(aq) àBr2(aq) 2Cl-(aq)The solution turns orange as bromine is formed, becausechlorine displaces bromine. This shows chlorine is morereactive than bromine.bromine iodide ions à iodine bromide ionsBr2(aq) 2I-(aq)àI2(aq) 2Br-(aq)A dark red-brown colouration is seen as iodine is formed,because bromine displaces iodine. This shows bromine ismore reactive than iodine.The halogen atoms gain an electron each from the halideions (reduction). The halide ions lose an electron each tobecome a halogen (oxidation). This is a redox reaction
We can conclude that reactivitydecreases as we go down Group 7.This is the opposite trend to whatwe saw with Group 1.We can use this to makepredictions about the reactivity offluorine, and of astatine: We predict that fluorine will bevery reactive – the most reactivehalogen. We predict that astatine will bethe least reactive of thehalogens.FClBrImostreactiveleastreactive
Separate SciencesExplaining the order of reactivity in Group 7Group 7 elements react byattracting an electron tocomplete their outer shell.The nearer the positivelycharged nucleus the outershell is, the easier it is forthe nucleus to attract anelectron from another atom,so the more reactive theelement is.[2,7]increasingreactivity[2,8,7][2,8,18,7]
Group 1 metals all react with water to produce alkaline solutions of metal hydroxides (this is why they are called alkali metals). They all fizz, producing hydrogen gas. For these reasons we can consider Group 1 a chemical family. Li, Na and K float and move around on the surface of the wate
Chemical Formulas and Equations continued How Are Chemical Formulas Used to Write Chemical Equations? Scientists use chemical equations to describe reac-tions. A chemical equation uses chemical symbols and formulas as a short way to show what happens in a chemical reaction. A chemical equation shows that atoms are only rearranged in a chemical .
Levenspiel (2004, p. iii) has given a concise and apt description of chemical reaction engineering (CRE): Chemical reaction engineering is that engineering activity concerned with the ex-ploitation of chemical reactions on a commercial scale. Its goal is the successful design and operation of chemical reactors, and probably more than any other ac-File Size: 344KBPage Count: 56Explore further(PDF) Chemical Reaction Engineering, 3rd Edition by Octave .www.academia.edu(PDF) Elements of Chemical Reaction Engineering Fifth .www.academia.eduIntroduction to Chemical Engineering: Chemical Reaction .ethz.chFundamentals of Chemical Reactor Theory1www.seas.ucla.eduRecommended to you b
Modern Chemistry 1 Chemical Bonding CHAPTER 6 Chemical Bonding SECTION 1 Introduction to Chemical Bonding OBJECTIVES 1. Define Chemical bond. 2. Explain why most atoms form chemical bonds. 3. Describe ionic and covalent bonding. 4. Explain why most chemical bonding is neither purely ionic or purley 5. Classify bonding type according to .
Word & Chemical Equations Scientists represent chemical reactions in two ways: Word equations – uses chemical names, plus signs, and an arrow to show the reaction. Example: Chemical equations – uses chemical formulas, plus signs, and an arrow to show the reaction.States of matter are also shown in subscripts after each chemical substance. Example:
Writing Chemical Formulas and Chemical Reactions Chemical Formula Chemical formulas are a useful way to convey information about a compound such as: ¾ What elements make up the compound ¾ The ratio or number of atoms in the compound The chemical formula has different meanings depending on the type of intramolecular forces holding
Chemical Equations and Reactions What is a Chemical Equation? A Chemical Equation is a written representation of the process that occurs in a chemical reaction. A chemical equation is written with the Reactants on the left side of an arrow and the Products of the chemical
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from atoms of all other elements Chemical bonds hold compounds together Chemical bonds may be ionic or covalent NOW, you will learn About chemical changes and how they occur About three types of chemical reactions How the rate of a chemical reaction can be changed KEY CONCEPT Chemical reactions alter arrangements of atoms.
