A central nucleus. Protons have a positive charge Electrons have a negative charge

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1 Atomic Structur Lss than ninty yars ago scintists blivd that atoms wr tiny solid sphrs lik minut snookr balls. Sinc thn it has bn discovrd that atoms ar not compltly solid but hav innr and outr parts. To know about th sub-atomic particls and thir proprtis To intrprt information givn on sub-atomic particls. A cntral nuclus Outr shll or orbit To mak a modl atom, a golf ball could b usd to rprsnt th nuclus and th outrmost row of sats in an Olympic Stadium could rprsnt an Aftr many xprimnts atoms wr brokn up into smallr particls calld lctrons, protons and nutrons. Ths particls hav diffrnt proprtis. 4 nutrons 3 protons 3 lctrons n p n p n n p Protons hav a positiv charg Elctrons hav a ngativ charg Nutrons hav no charg ( thy ar nutral) What can you say about th ovrall charg of this atom? This atom could b drawn in svral ways to show th sam information. W could r-draw this atom of lithium to show whr positiv and ngativ particls ar found OR w can summariz th numbrs of ach kind of particl. 3p 4n 7 3Li (2,1) Protons dtrmin whthr an atom is an atom of gold, lad or whatvr. Elctrons hav can hlp to balanc th protons to mak th atom nutral but can also caus atoms to bcom chargd Nutrons hav no charg but thy ar about th sam mass as protons and hlp giv th nuclus xtra wight. Elctrons ar much lightr ( / th mass of a proton) 1 Which particl is found in shlls around th nuclus 2 Whr is most of th mass of an atom found? 3 Look at th numbrs usd to dscrib th lithium atom. What do ths parts man? 7= 3= 2,1= 4 Complt th following tabl Proton Positiv charg Mass = 1 Elctron Mass = &!$ Found in th nuclus Mass=

2 Nuclus Numbrs Th two numbrs usd to dscrib th nuclus of an atom ar calld th mass numbr (=protons + nutrons) and th atomic numbr (=protons only). To us dfinitions of mass and atomic numbrs to dtrmin nuclar structurs To rcall how nutral atoms ar balancd 16 Q1 Why is hydrogn th odd-on-out? Q2 Scintists us atomic numbr to lmnts in ordr, if mass numbr was usd instad how would this ordr chang?

3 Isotops A sampl of pur chlorin dos not contain idntical atoms. Som of its atoms ar havir than othrs. Howvr apart from thir xtra mass, thy smll and bhav th sam. To rlat mass and atomic numbrs to amounts of subatomic particls To know what an isotop is. Lightr chlorin atom Ratio of atoms Havy : Light : Havir chlorin atom Molculs of chlorin ar diatomic and so ar writtn as Cl 2 17p 18n 17p 20n This chlorin atom has th symbol and numbrs Cl (2,8,7) Th havir atom of chlorin has th symbol and numbrs Cl (,, ) Atoms of th sam lmnt which hav th sam numbr of diffrnt numbrs of ar calld isotops. (or lctrons) but Compt th following tabl on isotops. Normally isotops of a chmical lmnt ar givn th sam nam but rfrrd to as (g) chlorin-35 or chlorin-37. Howvr hydrogn is a spcial cas and its isotops hav spcial Sinc on atom in four is havy w can us this fact to calculat th avrag mass (numbr) for chlorin avrag

4 Elctronic Structur Th arrangmnt of lctrons around an atom is closly linkd to its position in th priodic tabl AS2bHF Complt ach box so that it contains th nam of th lmnt and (a) th atomic numbr (b) th corrct arrangmnt of lctrons g 2,8,1 (c) th corrct shll/orbit diagram with X's for lctrons. To rcognis pattrns in th lctronic structur of th first 20 lmnts To rlat shll structur to its position in th Priodic Tabl Dscrib som pattrns you hav spottd :

5 Atoms and Priodic Tabl Group numbrs To rlat atomic structur to its plac in th Priodic Tabl st 1 priod nd 2 priod rd 3 priod th 4 priod th 5 priod th 6 priod Magnsium is found in th third priod and in group two. It has thr shlls and two lctrons in its outrmost shll. 12p 12n Fluorin is found in th scond priod and in group svn. It has two shlls and svn lctrons in its outrmost shll. 9p 10n Potassium is found in Boron is found in 19p 20n 1p 0n Although hydrogn is a gas it is put in Group 1 with th Alkali Mtals bcaus Th Nobl Gass ar spcial. Thy ar calld Group 0 bcaus 2p 2n 10p 10n

6 Ions During a chmical raction atoms combin with on anothr. For xampl To know that atoms can los or gain lctrons to bcom ions To us atomic diagrams to idntify +v or -v ions Sodium + Chlorin => Nutral 23 Na 11 Nutral 35 Cl 17 Th chang in nam from chlorin to chlorid tlls us that th atoms hav also undrgon a chang. 12n 11p Th lctron arrangmnt of chlorin starts off as (,, ). 11 lctrons and 11 protons 17 lctrons and 17 protons In a chlorin atom thnumbr of lctrons quals th numbr of and so th atom is nutral. As mtal atoms of sodium ar brought clos to non-mtal atoms of chlorin, individual lctrons artransfrrd- jumping across 12n 11p 20n 17p Th innr shlls ar ignord bcaus thy ar alrady full. Th lctron arrangmnt of sodium now bcoms (, ). In this sodium particl th numbr of ngativ lctrons is than th numbr of positiv protons. It is now a chargd ion Th lctron arrangmnt of chlorid now bcoms (,, ). In a chlorid particl th numbr of ngativ lctrons is than th numbr of positiv protons. It is now a chargd ion To show that th atoms hav changd into ions, chlorin is rnamd chlorid and ach ion is + givn anw symbol Na for th sodium ion and for th chlorid ion. This chang from nutral atom to chargd ion also happns for many othr lmnts g Zn => Zn p 4n 10 9p 10n 0 1p 0n 18 20p 20n 10 8p 8n Lithium ion writtn as Li + Fluorid ion writtn as S - Hydrogn ion writtn as Li + Calcium ion writtn as Li + Oxid ion writtn as S -

7 Ionic Bonding Atoms ar nutral particls. Undr crtain conditions, whn atoms combin thy bcom chargd particls calld ions. To b familiar with th diffrnt typs of bonding To show how diffrnt atoms chang as thy bond togthr. W say that th chargd particls ar hld togthr by ionic bonding 7 3Li (2,1) + v Elctron jumps across 19 9F (2,7) Nutral atoms Chargd Ions v v + v v + v + v v + v v v + v v + v Wll packd arrangmnt of ions in a (giant) solid lattic tc using millions of particls Using th following information on th starting nutral atoms, show how ths would form ions which would thn cling togthr to form a solid compound. Sodium chlorid Na (2,8,1) 17Cl (2,8,7) v Magnsium oxid Mg (2,8,2) 8O (2,6) v v v Magnsium fluorid F (2,7) 12Mg (2,8,2) 9F (2,7) Now on lind papr show how TWO sodium atoms would form ions with ONE oxygn atom would turn into sodium oxid.

8 Covalnt Bonding It is possibl for atoms to join togthr and stay nutral. This is calld covalnt bonding. Th word covalnt mans to shar (a pair of) lctrons 19 9F (2,7) To b familiar with th diffrnt typs of bonding To show how diffrnt atoms chang as thy bond togthr. 19 9F (2,7) covalnt bond Nutral atoms Nutral molcul Molculs not attractd to ach othr and so normally form a liquid or a gas Rmmbr th whol point of atoms joining togthr is so that thir outrmost ring of lctrons bcoms filld compltly. Tasks Draw dot and cross diagrams to show th covalnt bonding that kps togthr ths molculs. Mthan gas Ammonia gas Mad from ths atoms C (2,4) H (1) H (1) H (1) H (1) N (2,5) H (1) H (1) H (1) H H _ C _ H H In a prvious topic about Oil you drw mthan gas out with a stick pictur Draw out ammonia as a stick pictur In a stick pictur, ach dash rprsnts a covalnt bond. It also rprsnts a crtain numbr of lctrons - how many lctrons is this? Som substancs contain a doubl bond g oxygn O=O. How many lctrons ar involvd in th doubl bond which holds th atoms togthr? Draw out th following molculs using dot and cross (you do not hav to show th nuclus) Covalnt 35 17Cl (2,8,7) 35 17Cl (2,8,7) Covalnt H (1) 8O (2,6) 1 1H (1) Covalnt (Doubl bond) 16 8O (2,6) 16 8O (2,6)

9 Covalnt Bonding In covalnt bonding, lctrons ar not compltly transfrrd from on atom to anothr lik ionic bonding Instad thy ar shard by both atoms. To b familiar with th diffrnt typs of bonding To show how diffrnt atoms chang as thy bond togthr. Covalnt Bonding Th normal numbr of bonds which an atom will mak can b asily workd out. X Y X C O N X Y X X Y X Carbon has four outrmost lctrons (it is also in Group 4) and will form four covalnt bonds Oxygn has six outrshll lctrons (it is also in Group 6) and will form two covalnt bonds Non has ight outrshll lctrons and will form no covalnt bonds Thr is a link btwn th numbr of covalnt bonds which an atom will form and its outrmost lctrons Dscrib this link Q1 Which Group of th Priodic Tabl is Nitrogn found in? N Q2 How many covalnt bonds will it form? F Q3 Which Group of th Priodic Tabl is Fluorin found in? Q4 How many covalnt bonds will it form? Th numbr of covalnt bonds which lmnt can form is shown blow in a diffrnt way with sticks Hydrogn Oxygn Nitrogn Carbon only 1 bond always 2 bonds always 3 bonds always 4 bonds H O N N C C O N C C Us ths to hlp draw out th stick diagrams for th following substancs on lind papr Mthan, CH Ethan, C H Watr, H O, Ammonia, NH Mthanal, CH O " $! Ths ar slightly mor difficult challngs Ethn, C H Carbon dioxid, CO Dinitrogn trioxid, N O "!

10 Mtallic Bonding Chmical bonding involvs lctrons which ar ithr shard or transfrrd btwn atoms. Elctrons ar particularly important in holding mtal atoms togthr. To b familiar with th diffrnt typs of bonding To show how diffrnt atoms chang as thy bond togthr. Mtallic Bonding Al 3+ Al 3+ Al 3+ Us th information opposit answr ths qustions : 1 Which typ of bonding (covalnt/ionic) is mtallic bonding most lik? Explain your choic. Al 3+ Al 3+ Al 3+ 2 What diffrncs ar thr btwn this typ of bonding and mtallic bonding? Th outr shll lctrons on ach mtal atom ar fr to mov btwn atoms. This givs positiv ions surroundd by a 'glu' of lctrons. 3 Why ar mtals abl to conduct lctricity? Mtals conduct lctricity wll. This diagram shows a clos up of currnt flowing through coppr wir. currnt of moving lctrons Th following tabl looks at Group 1 of th Priodic Tabl, th family of ractiv mtals calld Alkali mtals. Lithium Sodium Potassium Rubidium Casium Full 3p 4n 11p 12n 19p 20n 37p 49n 55p 78n Proprty Atomic mass Mlting point ( º C) Dnsity (g/cm³) Elctrica m-¹) Thrmal (W m-¹k-¹ Conductivity l ( Conductivity 4 Why ar ths lmnts placd in th sam group of th Priodic Tabl? 5 Which on is hld togthr with th strongst mtallic bonding? Explain your answr 6 Which lmnt do you think loss its outrmost lctron most asily? Explain your answr. 7 Plot a lin graph of ithr th thrmal or lctricity conductivitis against dnsity. What gnral rlationship is thr btwn th conductivity of ths mtals and thir dnsitis.

11 Explaining Ractivity Som lmnts ar mor ractiv than othrs. This is closly rlatd to th lctrons in th outrmost shll. To apprciat that diffrnt atoms rquir diffrnt I.E.'s To rlat ractivity of atoms to thir Ionization Enrgis. lctron knockd off incoming bam By focusing a bam of lasr light on to a sampl of sparat atoms, on lctron in th outrmost shll can b mad to fly off. This is calld ionization. Th nrgy of th lasr bam has to b carfully slctd to tak into account th numbr of lctrons, th numbr of shlls and th numbr of protons (which try to kp th lctrons in plac). Th nrgy of th bam usd to knock out lctrons is calld th ionization nrgy. This is shown blow for th first twnty lmnts in th Priodic Tabl Plot a graph of atomic numbr (x-axis) against ionization nrgy (y-axis) Suggst a valu for th ionization of potassium On your graph labl Group 1 lmnts (H, Li, Na and K) and Nobl Gass (H, N, Ar). Explain why Nobl Gass ar th last ractiv lmnts and Group 1 ar th most