Module 2.2 Flashcards
A quick recap of GCSE
-Electrons exist in electron shells .
The first shell has two electrons .
-The second shell can hold up to eight electrons .
-As well as the third before we put electrons in the fourth shell .
-KEY ; as we move further from the nuecleus , the energy of the shells increases .
-Each shell is given a number …
… scientists call this the prinipal quantum number or ~n”
-The first shell has the principal quantum number 1 .
-The second shell has a principal quantum numebr 2 .
-Third has 3
-The fourth ha four .
How do we clculate the mac=ximum nmber of electrons that each shell can hold .
Maximum n.o of electrons = 2nsquared
CHECK SHEET FOR THE SHELLS .
Key; The electrons in a shell are found in regions called atmomic orbitals .
So what are atomic orbitals ?
-Atmoic orbitals ; a region around the nucleus that can hold up to two electrons with opposite spins .
-You do need to know electrons can either have an up spin or down spin .
-When we have two electrons in the same orbital , THESE TWO ELECTRONS MUST HAVE OPPOSITE SPINS .
-WE CANNOT have two electrons both with an up spin or both with a down spin , must be OPPOSITE .
GCSE RECAP AGAIN
-At GCSE we considered an electront obe a particle .
-HOWEVER , at A-elevel , an electron is considered to be a cloud of NEGATIVE CHARGE /
-The negaitve charge cloud has the SHAPE OF THE ORBITAL , occupied by the elctron
-Scientists can never be certain of the exact LOACATION of an electron …
… however , the atomic orbital shows us a 95% probability of where an electron exists .
There are several different types of atomic orbitals + each one has a letter
These are S,P,D,F
S OrbitaL (CHECK SHEET AND TABLE ON SHEET )
-hAS A SPHERICAL SHAPE .
-EVERY ELECTRON SHELL CONTAINS A SINGLE s ORBITAL.
-YOU NEEED to know how to draw it so pracitseee.
P ORBITAL check sheet and table once again.
There are three p orbitls . They are shaped a bit like a dumbell .
-EVery electron shell aparfrom the first one contains three p orbitals .
D orbitals .
there are five d orbitals but these re complicted shapes we don;t need to know .
-every shell apart from shells 1 an 2 have five d orbitals .
f orbitals
there are seven different f orbitals . wE FIND THESE IN SHELLS FOUR AND ABOUVE .
remember ; EACH ORBITAL CAN ONL HOLD A MAXIMUM OF TWO ELECTERONS . (add up all the electorns in each shell and check table )
subshell
all the orbitals of the same tpe in the same shell .
key;
different subshells have different energies .
-As we move AWAY from the nueclues , the energy of the subshells increases /
in orderto show how electrons fill the orbtials , we need to follow three rules :
…
rule 1
orbtials with the lowest energy are filled first .
rule 2
we can have up to two electrons in the same orbitals ut they must have opposite spins .
rule 3
if we have orbitaals wtht he same energy , then we have to put electrosn into invidual orbitals before we pir them .
-this is because electrons int he same orbital repel .
CHECK SHEET FOR EXAMPLES .
sheck example on electron configuration part 2 - whats interesting about shell four .
-the energy of the 4s subshell is less than the energyof the 3d subshell .
-Meanign we fll in the 4s subshell befpre we start filling in the 3d subshell .
check sheet - what is star one saying ?
check sheegt
WHATA RE THE TWO EXCEPTIONS TO THE ELECTRON CONFIGURTIONR UELE .
CHROMIUM AND COPPER .
-iN BOTH cases 4s subshell contains only one electron eventhough there are electrons in the 3d subshell.
-This is because the 3d subshell is more sstable when it is either half full /completely full
In the case of chromium ; by having only one elecron in the 4s subshell it can have a half full 3d subshell .
in the case of copper , by onl having one electron int he 4s subshell it cn have a compeltleyf ull 3d subshell .
do more practise ont his !!
…
CHECK SHEET
Scientists divide the periodic table into different blocks , each block is named fter the subshell containign the highest energy electron for the elemnts in that block .
short hand configuration (sodium is example .
1.look at the position of sodium on the perioidc table .
stage two
looka t the noble gas in the period before sodium (neon=10 electrons).
stage 3
compare the elctron configurations compare of neon compred to sodium .
stage four
tje onner electrons hells of sodium ajve the same electron confiuguration as neon .
-Remeer the elctrons in the inner shell are NOT INvolved inc hemical reactions is ontl the ONES IN THE outerhsell (so s31 for soidum)
stage five
so thartheer than writing out the whole electron configruation of soidum , we can represent the elcetorns in the inner shel ike this .
-sodium (ne)3s1 –> shorthand . IN EXAM WRITE GFULL HAND UNESS ASKED TO .
Use manganese as an example .
-check sheet .
-dblock still showed in electron configuration eventhough not outershella s electrons in the dsusbhell are invovled in the chemical reaciton .
-ALWAYS loose fromt he 4s subshell first=
Why do elements react and bond together ?
-elements invovled in chemical reactions will often become more stable by combining with other elements or transferrign electons .
-The most stable and unreactive elemnts are the noble gases .
-these elements re stable because they contain a full outershell of electrons .
(full outer shell inerms of orbitals)
-eight electrons in the outer shell of a noble fas , are made up of two int he s orbital and two each in the three p -orbitals .
-during reactions , other elemnts iwll bond with a tendecey to acquire this noble gas conficuration .
-s, p bodning are used for bodnignsuualuf r firt 18 .
types of chemical bonding
-Chemical bonds are classified into three main tpes ; ionic , covalent and metallic .
-A compound is formed when atoms of different elemnts are alwas in same proptions (h20always has two hdyrogen atoms to one oxygena tom . )
Ionic bonding
-In general , ionic bdoning occurs in compound consiting of a metal and a non-metal .
-if w eimagie a bond forming between atoms ,e elctros are tansfered fromt h metal atom tot he non-metal atom to form opposiely charegd ions that attrct achother .
Covalent Bonding
-occurs in compounds consisting of two non-metals .
-If we imagine BOND FORMING BEWEEN ATOMS , ELECTRONS ARE SHARED Between the atoms and are atracted tothe nueclei of both bonded atoms .
-covalent bdonging will also usuallyr esult in the elemtn inovlved achieing noble gas configurtations .
metallic bonding
-occurs in metlas .
-electron are shared between ll the atoms .
Ionic bonding how it works
-electrons are transferred from the metal atom to the non-metal atom .
-opposielyc harged ions are formed ,w hich are bonded together by electrostatic atraction .
-the metal ion is positive ..
-non -metal ions is negative .
giant ionic lattices
-each ion id surroudded by oppositelyc hrged ions .
-These ions atract each other from all directions , forming a three-dimensional giant ionic latice .
giant ionic lattices properites
Each ion attracts oppositelc hrged ions from al directions ;
-Each ion is surrounded by oppositelyc harged ions .
-The ions attracts each othe r, forming giant ionci alttice .
-because giant ionic latices involve hueg amouts of electorstatic atreaction between ions ,t hry have unique propeties .
Properties of ionic compounds - High meltign and boling poitns
SOLID AT ROOM TEMPERTURE - a large moutn of energy is needed to break the strong electorstatic bonds that hold the oppositely charged ions together in the soidl lattic e.
therefore they ahve hig mp p .
electrical conductivit of ionic compounds
-IN SOLID ionic lttice
-ions re held in ficed postions and no ions can mvoe .
-The ionic compound does not conduct eleictiruu .
electrical conducitivity of ionic compounds (2)
-the solid lattice breaks down and the ions are free to move .
-The ionic compound is now conductor of electircy .
Ionic compounds - solubilitt
-an ioionc lttice dissolves (soluble) in polar solvents , such s wte r..
-Pola solvents contain substncs that have polar bonds .
-a polar bond occur between atoms that do not share electrons equally nd it reuslts in the atoms having very smallc ages .
ioncic compoounds - solubilit part twp
polar water moelcues beak downa niconic lttice by surroudnign each ion to form a solotuion .
-the slight changes within the polar substance are able to atracr the chargd ion in the ionci lticie .
Covalent bonding -shared pairs of electrosn
-the negativley chrged shared pair of electrons is ttrcted to the positive charge of btoh nuclei .
-This atrction overcomes the repulsion between the two postiecl chrged nuclei .
-the resulting attraction is the ocvlent bond tht hodls the two atoms together .
-twpo electrons are shared . This is in contrast to the trnsfer of ele ctrons thr result in an ionic bond .
average bond enthalpy
-not all covalent bonds are the same strength . Some are much stronger than others ,w hich means that more energyw ould be required to break them , e.g during a reaction .
How are atoms in a solid metal held together by metallic bonding ?
-in metallic bonding , the atoms are ionsied . Positive ions (cations) ocupy fixed positions in a lattice .
-the outer shell electrons are delocalsied - they are shared between all the atoms in the metallic strcuture .
-metal is held together by the attractions between all the positive ions + the negative elctrons - especially the delocalised electrons .
Whya re metals able to conduct electricty ?
-As they have delcoalised electrons can move freely anwayhere within the emtallic strcutrue .
-Allowing the metal to conduct electricity even in the solid state .
why are metals mallebale + ductile ?
-as the delocalised electrons are largely responsible for these properties .Because , they can move , the etallic strucutres has a degree of ‘give’ which allows atom or layers to slid past eachother .
why do metals (typically) hve high metlign boilign poitns .
The electrons are free to mvoe throughout the strucutre , but the positive ions remains where thrya re .
-The attrction between the positive ions +the negative delocalised elecgtrons are very strong .
- high tmeperture is needed to overome the emtallic bond and disoldged the iosn foromt heir rigiod positos in the littic e.
How does the volume + tomic radius of the metlas in groups 1,2,3 affect the bond strength + thus the melting points of the metls ?
-For each sucesive grop , element ahs a giant metalic lattice , the nuclear charge increase , as does the numebr of electrons in the outershell . As gthere are more electrons in as you from goup 1-3 , so most electrons to form covalent bond .
-There is a harp decrese icncresing meting points s the elmets hae simple moleculr strcutures .
-Each indivuals molecule is atrrced to other by relativelu wek intrrmoleculsr forces .
-Atomic radius decrese s you go down group 1,2,3
How is metallic bodning different to covalent + ionic bodning .
check squilaci metallic sheet .
Dative covalent bond ?
When atom uses a lone pair of electrons to form a covalent bonds , .
Rules for a dative covalen tbond
-the acceptor must be electron deficent .
-Avaialbe orbitals for the electrons to occupy .
first ionisation energy
ennergy needed to remove one mole of electrons from one mole of atoms in their gaseoust state to form one 1+ ions also in their gaseouss stae ..
Check magnesium
Mg —> Mg+e-
-1 mole of magensium ions + turn into a gas .
-Includign state smbol has .
-Then take one electron from every atom to form one mole of 1+ magnesium ions in thier gasesous state . The neegry needed ot do this is first ionsiation energy .
Once we remove an electron , we can continue to remove lectrons to measure the ionsiaton energy each time .
Mg —> Mg1++E-
Looking above we remoeved sanotehr electron this is second ionsiaton energy
the energy needed to remove on emole of electrons from one mole of 1+ ions in their gaseous state to form one mole of 2+ ions in their gaseous stae .
-can contine reomving electron and measuring their ionsiaorin energye ach itme
these are sucessive ionsiatoine enrgies .
Workout the iosniation energy
ITS THE SAME AS THE CHARGE PRODUCED
Key about iosniation energy ;t he elctrons in an tom are attracted to the positive portons int he nucleus .
-The GREATER the atraction between the outer electeons + the nucleus , the GREATER the ionsiatoin enegry ./
FIRST FACTOR THAT AFFECTS IONISAITONE ENRY ;
-The distance between the nucleous + outermost electorn (Atomic radius)
-AS ATOMIC RAIDUS ICNREASE S.
-THE FORCE OF ATTRaction between the positive nuleus + otuer electron decreses,
SECOND FACTOR THAT AFFEC IONSIATION NERGY .
Charge on the nueclues
-Eleectors are attracted to the positvley chagred portos in the nculeus
THE greter nummber of portons = greater force of atraction between outer electrons + nucles .
THIRD FACTOR THT AFFECTS IONSIATION ENERGY
SHEIDLIGN
-Electrons int he outer shell re repelled b electrons in the inner shell .
-Sheiidlings effect reduced the attaction ebtween the outer electrons and the nucleus .
How does sucessive iosniatoin tell us about how eelctrons are ARRANGED IN ATOMS ?
cHECK GRAPH star one
This is ocrgen rph
-graudal increase in ionsation energya s we have just removed th first isx electreons .
-AS we remove each otuer electrons , the outer shells are PULLED LSIGHTLHY CLSOER TO THE NUCLEUS .
-MEANING ,t here is a grater atteaction between the outer electron + nucleus causing IONISAITON ENERGY TO INCREASES GRADUALLy .
star two
-Massive increase in ionsiation energy ,w ehn we remove the SEVENTH ELECTROn .
-As compred to the second electron shell . THE
FIRST ELECTRON SHELL IS CLOSEER TO THE NCUELUS ND THE ELCTROS INT HE FIRST SHELL EPXERIECE MUCH LESS shielding .
-so electrons int he first hsell hav agreater ATTRACTIOn to the ncuelus comapred to secon shell .
-eexpalingign why ionsiation energy is GREATER FO R7TH 8 TH ELECTRONS COMAPED TO FIRST SIX
EXAM ; identiy eement using iosiatione energy data
-Given a grpah .
-First si ionsiatione nergyies , workout element .
