Structures and BondingStructures and Bondingchemistrychemistry
17/06/13The structure of the atomThe structure of the atomELECTRON –negative, massnearly nothingPROTON –positive, samemass asneutron (“1”)NEUTRON –neutral, samemass as proton(“1”)The Ancient Greeks used to believe thateverything was made up of very small particles.I did some experiments in 1808 that provedthis and called these particles ATOMS:Dalton
17/06/13Mass and atomic numberMass and atomic numberParticle Relative Mass Relative ChargeProton 1 1Neutron 1 0Electron 0 -1MASS NUMBER = number ofprotons + number of neutronsSYMBOLPROTON NUMBER = number ofprotons (obviously)
17/06/13Mass and atomic numberMass and atomic numberHow many protons, neutrons and electrons?
17/06/13Electron structureElectron structureConsider an atom of Potassium:Potassium has 19 electrons.These are arranged in shells…NucleusThe inner shell has __ electronsThe next shell has __ electronsThe next shell has __ electronsThe next shell has the remaining __ electronElectron structure= 2,8,8,1
17/06/13IsotopesIsotopesAn isotope is an atom with a different number of neutrons:Each isotope has 8 protons – if it didn’t then it justwouldn’t be oxygen any more.Notice that the mass number is different. How manyneutrons does each isotope have?
17/06/13MendeleevPeriodic tablePeriodic tableThe periodic table arranges all the elementsin groups according to their properties.Horizontal rows are called PERIODSVerticalcolumns arecalled GROUPS
17/06/13H HeLi Be B C N O F NeNa Mg Al Si P S Cl ArK Ca Fe Ni Cu Zn Br KrAg I XePt Au HgThe Periodic TableThe Periodic TableFact 1: Elements in the same group have thesame number of electrons in the outer shell(this correspond to their group number)E.g. all group 1 metalshave __ electron intheir outer shellThese elementshave __ electronsin their outer shellThese elements have__ electrons in theirouter shells
17/06/13H HeLi Be B C N O F NeNa Mg Al Si P S Cl ArK Ca Fe Ni Cu Zn Br KrAg I XePt Au HgThe Periodic TableThe Periodic TableFact 2: As you move down through the periodsan extra electron shell is added:E.g. Lithium has 3electron in theconfiguration 2,1Potassium has 19electrons in theconfiguration __,__,__Sodium has 11electrons in theconfiguration 2,8,1
17/06/13H HeLi Be B C N O F NeNa Mg Al Si P S Cl ArK Ca Fe Ni Cu Zn Br KrAg I XePt Au HgThe Periodic TableThe Periodic TableFact 3: Most of the elements are metals:These elementsare metalsThis line dividesmetals from non-metalsThese elementsare non-metals
17/06/13H HeLi Be B C N O F NeNa Mg Al Si P S Cl ArK Ca Fe Ni Cu Zn Br KrAg I XePt Au HgThe Periodic TableThe Periodic TableFact 4: (Most important) All of the elementsin the same group have similar PROPERTIES.This is how I thought of the periodic table inthe first place. This is called PERIODICITY.E.g. consider the group 1 metals. They all:1) Are soft2) Can be easily cut with a knife3) React with water
17/06/13Newlands vs. MendeleevNewlands vs. MendeleevLi Be B C N O F Na Mg AlLi Be B C N O F Na Mg AlIn the early 19thCentury scientists knew about 60 of the 100 _______ wenow know of. It had also been seen that some elements had very similar_______ to each other. John Newlands was the first scientist to attemptto use these properties to put the elements into a ______ (in 1869):Mendeleev came along in 1869 and made a very important change: heincluded _____ to account for missing elements that hadn’t yet been__________.Using these gaps he could predict the properties of the undiscoveredelements by considering the properties of the known elements ______ andbelow it. Quite useful really, as the _____ gases (helium, neon and so on)weren’t discovered until 30 years later. We now use ______ configurationas a basis for grouping elements.Words – gaps, properties, noble, above, table,electron, elements, discovered
17/06/13BondingBondingHi. My name’s Johnny Chlorine.I’m in Group 7, so I have 7electrons in my outer shellI’d quite like to have a full outershell. To do this I need to GAINan electron. Who can help me?ClCl
17/06/13BondingBondingHere comes one of my friends,Harry HydrogenHey Johnny. I’ve only got oneelectron but it’s really close tomy nucleus so I don’t want to lostit. Fancy sharing?ClHCl HNow we’re both really stable.We’ve formed a covalent bond.
17/06/13BondingBondingHere comes another friend,Sophie SodiumHey Johnny. I’m in Group 1 so I haveone electron in my outer shell. UnlikeHarry, this electron is far away fromthe nucleus so I’m quite happy to getrid of it. Do you want it?ClNow we’ve both got full outer shellsand we’ve both gained a charge.We’ve formed an IONIC bond.NaOkayCl Na+-
17/06/13Covalent bondingCovalent bondingConsider an atom of hydrogen:Notice that hydrogen has just __ electron in its outershell. A full (inner) shell would have __ electrons, so twohydrogen atoms get together and “_____” their electrons:Now they both have a ____ outer shell and aremore _____. The formula for this molecule is H2.When two or more atoms bond by sharing electrons wecall it ____________ BONDING. This type of bondingnormally occurs between _______ atoms. It causes theatoms in a molecule to be held together very stronglybut there are ____ forces between individual molecules.This is why covalently-bonded molecules have low meltingand boiling points (i.e. they are usually ____ or ______).Words – gas, covalent, non-metal, 1, 2, liquid, share, full, weak, stable
17/06/13Dot and cross diagramsDot and cross diagramsWater, H2O:Oxygen, O2:OH HO OHHOO OStep 1: Draw the atoms withtheir outer shell:Step 2: Put the atoms together andcheck they all have a full outer shell:
17/06/13Dot and cross diagramsDot and cross diagramsNitrogen, N2:Carbon dioxide, CO2:Ammonia NH3:Methane CH4:H HNHHHHHCN NO OC
17/06/13IonsIonsAn ion is formed when an atom gains or loses electrons andbecomes charged:If we “take away” the electronwe’re left with just a positivecharge:This is called an ion (in this case, a positive hydrogen ion)+-+The electron is negatively chargedThe proton is positively charged+
17/06/13Ionic bondingIonic bondingNaNa+This is where a metal bonds with a non-metal (usually). Instead of sharingthe electrons one of the atoms “_____” one or more electrons to theother. For example, consider sodium and chlorine:Sodium has 1 electron on its outer shelland chlorine has 7, so if sodium givesits electron to chlorine they both havea ___ outer shell and are ______.A _______chargedsodium ionA _________chargedchloride ionAs opposed to covalent bonds, ionic bonds form strong forcesof attraction between different ions due to their opposite______, causing GIANT IONIC STRUCTURES to form (e.gsodium chloride) with ______ melting and boiling points:ClCl-
17/06/13Giant structures (“lattices”)Giant structures (“lattices”)+++++++++1. Diamond – a giantcovalent structure with avery ____ melting pointdue to ______ bondsbetween carbon atoms2. Graphite – carbon atomsarranged in a layeredstructure, with free _______in between each layer enablingcarbon to conduct _________3. Sodium chloride – a giant ionic latticewith _____ melting and boiling pointsdue to ______ forces of attraction.Can conduct electricity when _______.4. Metals – the__________ inmetals are free tomove around, holdingthe _____ togetherand enabling it toconduct _________
17/06/13Group 1 – The alkali metalsGroup 1 – The alkali metalsLiNaKRbCsFr
17/06/13Group 1 – The alkali metalsGroup 1 – The alkali metals1) These metals all have ___electron in their outer shellSome facts…2) Reactivity increases as you go _______ the group. This isbecause the electrons are further away from the _______every time a _____ is added, so they are given up more easily.3) They all react with water to form an alkali (hence theirname) and __________, e.g:Words – down, one, shell, hydrogen, nucleusPotassium + water potassium hydroxide + hydrogen2K(s) + 2H2O(l) 2KOH(aq) + H2(g)
17/06/13Group 0 – The Noble gasesGroup 0 – The Noble gasesHeNeArKrXeRn
17/06/13Group 0 – The Noble gasesGroup 0 – The Noble gasesSome facts…1) All of the noble gases havea full outer shell, so they arevery _____________2) They all have low melting and boiling points3) They exist as single atoms rather then diatomic molecules4) Helium is lighter then air and is used in balloonsand airships (as well as for talking in a silly voice)5) Argon is used in light bulbs(because it is so unreactive)and argon , krypton and neonare used in fancy lights
17/06/13Group 7 – The halogensGroup 7 – The halogensFClBrIAt
17/06/13Group 7 – The HalogensGroup 7 – The HalogensSome facts…1) Reactivity DECREASESas you go down the groupDecreasingreactivity(This is because the electrons are further away from thenucleus and so any extra electrons aren’t attracted as much).2) They exist asdiatomic molecules (sothat they both have afull outer shell):Cl Cl3) Because of this fluorine and chlorine are liquid at roomtemperature and bromine is a gas
17/06/13The halogens – some reactionsThe halogens – some reactions1) Halogen + metal:Na+Cl-Na Cl+2) Halogen + non-metal:H Cl+ Cl HHalogen + metal ionic saltHalogen + non-metal covalent molecule
17/06/13Displacement reactionsDisplacement reactionsTo put it simply, a MORE reactive halogen will displacea LESS reactive halogen from a solution of its salt.FClBrIDecreasingreactivityPotassiumchlorideKCl(aq)PotassiumbromideKBr(aq)PotassiumiodideKI (aq)ChlorineCl2BromineBr2IodineI2
17/06/13Halogen compoundsHalogen compoundsSilver halides (e.g. silver chloride, silver bromide etc)These are used in photographic paper. They are reduced bylight and x-ray radiation to leave a silver photographic image.Hydrogen halides (e.g. hydrogen chloride, hydrogen fluoride)When these dissolve in water they make acids and will turnuniversal indicator red.
17/06/13Electrolysis of brineElectrolysis of brinePositiveelectrodeNegativeelectrodeSodiumchloride (brine)NaCl(aq)Sodium hydroxide(NaOH(aq)). Used tomake soap, paper andceramicsSodium chloride (salt) is made of an alkali metal and ahalogen. When it’s dissolved we call the solution “brine”,and we can electrolyse it to produce 3 things…Chlorine gas (Cl2) – used tokill bacteria and to makeacids, bleach and plasticsHydrogen gas (H2) – usedto manufacture ammoniaand margarine
17/06/13Chemical formulaeChemical formulaeThe chemical formulae of a molecule or compound is simply away of showing the ratio of atoms in it. For example…Na Cl = sodium chloride (NaCl)K I = potassium iodide (KI)K NOOO= potassium nitrate (KNO3)
17/06/13Naming compoundsNaming compoundsRule 1– If two identical elements combine then thename doesn’t changeThis happens with the following elements:1) H22) N23) O24) F25) Cl26) Br2These elements always goaround in pairs (diatomicmolecules). For example,hydrogen looks like this:
17/06/13Naming compoundsNaming compoundsRule 2 – When two elements join and one is a halogen,oxygen or sulphur the name ends with ____idee.g. Magnesium + oxygen magnesium oxide1) Sodium + chlorine2) Magnesium + fluorine3) Lithium + iodine4) Chlorine + copper5) Oxygen + iron6) KBr7) LiCl8) CaO9) MgS10)KF
17/06/13Naming compoundsNaming compoundsRule 3 – When three or more elements combine and two ofthem are hydrogen and oxygen the name ends withhydroxidee.g. Sodium + hydrogen + oxygen Sodium hydroxide1) Potassium + hydrogen + oxygen2) Lithium + hydrogen + oxygen3) Calcium + hydrogen + oxygen4) Mg(OH)2
17/06/13Naming compoundsNaming compoundsRule 4 – When three or more elements combine andone of them is oxygen the ending is _____atee.g. Copper + sulphur + oxygen Copper sulphate1) Calcium + carbon + oxygen2) Potassium + carbon + oxygen3) Calcium + sulphur + oxygen4) Magnesium + chlorine + oxygen5) Calcium + oxygen + nitrogen6) AgNO37) H2SO48) K2CO3
17/06/13Balancing equationsBalancing equationsConsider the following reaction:Na OH HH HNaOHSodium + water sodium hydroxide + hydrogen+ +This equation doesn’t balance – there are 2 hydrogenatoms on the left hand side (the “reactants” and 3 onthe right hand side (the “products”)
17/06/13Balancing equationsBalancing equationsWe need to balance the equation:NaOH HH HNaOHSodium + water sodium hydroxide + hydrogen+ +NaOH HNaOHNow the equation is balanced, and we can write it as:2Na(s) + 2H2O(l) 2NaOH(aq) + H2(g)
17/06/13ElectrolysisElectrolysisElectrolysis is used to extract a HIGHLY REACTIVE metal.= chloride ion= copper ionWhen we electrolysedcopper chloride thenegative chloride ionsmoved to the positiveelectrode and the positivecopper ions moved to thenegative electrode –OPPOSITES ATTRACT!!!
17/06/13Electrolysis equationsElectrolysis equationsWe need to be able to write “half equations” to show whathappens during electrolysis (e.g. for copper chloride):2 22At the negative electrode thepositive ions GAIN electrons tobecome neutral copper ATOMS. Thehalf equation is:Cu2++ e-CuAt the positive electrode thenegative ions LOSE electrons tobecome neutral chlorineMOLECULES. The half equation is:Cl-- e-Cl2
Thank you for watching!Thank you for watching!Any questions please do ask Sandra