Module-3.1 Flashcards
Before the periodic tablle
-arostot;e beleived he world was mad eup of four elements - earth fire wate air and fire .
384-322 BCE .
-it could be argued that these four elemtns are similar to what we now call the sttes of mttter - solid liqui gs eith fire represenign more usunal phenomen sucha splasm .
PERIODIC TABLE 1. Antoinee 0 Laurent de Lvoiser
-1789
is now cisndired to be the first modern chemical textbook .
-in this he compiled the fist extensive list of elemnts , which he dusibed as ‘substances that coud not be broekn down further .@
WHAT was lavoisers list of elemnts
-Oxygen , nitrogen ,hydrogen , phosphours m meury zinc and sulfur ,.
-also disitnguished between metlss + non -metals ,
-unofrutntley it also included some compounds and micutr ,along witht emrs suchas ‘ligt; and ‘caloric’ heat which he belied to be material sustances .
- devleopmet of the periodic table
Jons Jakob Bezerlius
1828
-he published a table of atomic weights and determiend the compsotion by masso f many compounds .
-Berzelisus was also responsibel for introuvin lettter based symbosl for elements .
- development og the periodic tble Johann Wolfang Dobereiner
Dobereine rnoticed that certain groups of three leements .
-Ordered by tomic wiehgt would have a middle elemnts with a weeight and propeties (such s density) that were roughly n averga eof the other two elements .
THE TRIADS THAT Dobereine rconsdiered
-calcium strontium and brium .
-Chlorine bromine and iodien ,
-Litiium ,s odium and potassium
- development of the periodic table
-JOhn Newlands -devise a periodic table that had elemnts arraned in order of their relaitve aomic weihts .
-In1865 he suggested that rather than bein intraids , elements show simialr propeties tot eh elemens eight palces adfre it int he t bale .
-He called it his ‘law of octaves; .
5.development of the periodic table
dmitri Medeleev
-modern periodic table is based on theo ne publsihed by medeleev in 1869 .
-his table showed eleemnt otfrtrf by atomic weightd , similr to newlands and ordered periodically .
dmitiri edeelev (1)
-eleements withs imialr properies are rranged in verticals columns .
-gap were felt where no elements fitted the repeating patterns and the propeties of the missing elements were predicted .
-these missing elements hae eens ixned found nd atched .
elements Tht have been FOUND AND MATCHED MENDEELEV;S PREDICTION
Gallium , germainium , and scandium .
dmitiri mendeleev (2)
-the order of elements was rearranged where their properied did not fi .
-For e.g tellurium had a higher atomic weiht than iodine , but mendeelv rervesed them to make the properties fit with the res of th e table .
-The arrangeent of the element or groups of element in ord of their atomic weights corresponded to their os -capped valencies as well as thier distincitve chemical pepowperies
-Apparent series suchas , LI , Be , B , C, N , O and F.
6.development of the periodic table
1913-Henry Moseley determined the tomic number for ll the known elements .
-Moseley mdoifided MENDEELV’S peridoic law to red that the porpoeties of the lements vary periodically with rhier atomic numbers rather thn atomic weights .
-moseleys modifided periodic law put the elements tellurium and iodine in the correct order , a it did ofr argon nd potssiuma nd for cobalt nd nicle .
7.Development of the periodic table
-Seaborg dISCOVERED the transuranic elements fom 4 plutonium to 102 nobrlium ,
-He lso remodelled the periodic tbale by plcting the actnicide seirs belows the lanthanide series at the bottom of the table .
In the periodic tbale , elemnts are ordered by increasing atomic number .
The period number tells us the number of highest energy electron shell for the elemnts int hat period .
(e.g all the elements in period 4 , have the highest energy electron is 4 .)
KEY - there is a repeating trend in the propeties of the element across a period .
E.g —> period 2 , LEFT side elements are metals ,but on he right they re non - metals . This repeats to period three also .
Beteen the metals and non-metals we have the metalloides .
Metalloides have properties of oth metals and non-metls .
-Same tredn repeating across other periods . Scientiss calla pattern of repeatin trends PERIODICIT .
As we saw before ,e ch period represents a new highest energy electron she..
-Period 1 , highest energy electrons are in the first shell .
-period 2 , highest energy electrons are in shell 2
For each electron shell , electrons fill the s subshell before they fill the p subshell .
(check video if stuck )
KEY ; filling of electrons in subshells follows a periodic pattern .
-Within the highet energys hel , the s subshell fills beforore the p susbshell .
Each block in the periodic table is named after the sushell containign the highest energy electron for elements in that block .
Within a group , each elemnt has the same number of electrons in the outer subshell .
E.g , all the elemnt sin group 1 have one electron int heir outer s subshell .
As we move cross a period …
Each element has one more protoon in its nucleus than the element to its left .
We cannot measure the radius of an electron of an atom directly , as electron clouds , do not have a clear cut off point .
-Way of calculting atomic raidus it to look at the pair of idenitcal atoms , that have formed a bond .
-We take the atomic raidus as half the distant between the nuclei of the two atoms .
check sheet for atomic raidus of elemnts lithium–> calcium
ONE trend we can see is that ;
-Atomic radius decreases as we move across a period , from left to right .
look at period 2 we can see it decreasing from LITHIUM TO FLUROINE . and atomicrdius deceasing again from sodium tochlorine .
Going to explain why , the first trend happens using period 2 , but this applies to the other periods as well .
-As we move across a period (left to right ) , each element has one more proton in its nucleus than the elemnts before .
-Meaning that h POSITIVE CHARGE in the nucleus increases across a period ,
-Due to this , there is an INCREASED ATTRACTIOn , between the nucleus and the electrons .
-DRAWING the electrons CLOSER to the nucleus .
-Causing the atomic radius to decrease across the period .
Remember ; Outer shell electrons are partially shielded , fromt he attraction of the neuclues by electrons in innershells .
However , elements in period 2 , only have one inner electro shell .
-Meaning sheidling due to the inner elecron shell is the same across the period .
Second trend
-Atomic radius increses MOVING DOWN the group , Can see this , check sheet , with Lithium , Sodium and Potassium .
-As we move down group 1 , atomic radius increases (same trend with group 2 ) .
-The number of electron shells increases ,a s we move down the grup .
-So the outer electron shell is furhter from the nucleus .
-Each element has one more , full inner electron shell .
–ncreasing the amount of shielding between the nueclues and the otuer electron .
-Therefore ,t here is less atraction between the outer electron and the nueclues .
-Therefore ,t he atomic radius INCREASES , moving down a group .
Remember the defenition of first ionisation energy
the energy needed to remove 1 electron from each atom of an element in 1 mole of gaseous atoms, to form 1 mole of gaseous ions with a +1 charge.
BECAUSE OF THIS
-Atomic radius decreases across a period .
-Botht he increased nueclear charge and decreased atomic radius .decreases across a period .
Botht he increased nucler chagre nd decreased atomic radius means that the outer electrons are more attrcted to the nucleus .
-Causing 1st ionisation energy to increase across a period .
check shee for table
-How first ionisation energy varies across
-Plotted period 2 st ionisation energy against the atomic number of each element.
As you can see , the first ionisation energy ,t ends to icnrese as we move acros a period from elft to right .
-Moving across a period , the postive charge in the nucelus increase ,a s the number of protons increases .
-This increases the atraction between the nucelus and the electrons .
In all of these elemnts , we are remoivng on eelectron fromt he second electron shell .
Meaning the sheilding effect due to the inner electron shell is the sme for ehc eleemn .
-Boron oxygen do not fit the patern of increasing first ionisation energyu .
-Need to look t subshells Li+E removing electron from 2S SUBSHELL .
-However , for Boron , outer electron is int he 2P subshel and 2P subshell has a higher energy than the 2S subshell .
-Meaniing , it takes less energy to take an otuer electron from Bboron comapred o BE .
-Which s why it has a lwoer st ionsatione nergy than Beryilium .
Ionisation energy decreases at Oxgen ..
-Look at the subshell one of the 2p orbitals contians a PAIR OF ELECTRONS .
-These electros repel eachother
This means it taes less energyt o remove one of these electrons .
-Than if the electrons were in sepeatre orbitals .
Which is why Oxgen is the s ionsiatione egry is less thn N .
-Simialr paern for priod 3 (ame dips ut were are looking at the 3rd electrons hell , NOT the second shell .)
Check the ionsiation energies for group 1
-Ionisation energy in group 1 ,
-as you can see first ionisation energy decreases as we go down group.
–THIS IS DUE TO TWO FACTROS
FACTOR ONE
-As you go down the group , atomic raidus increases .
-Meaning hte outer elecron shell is furhter way from the nucleus .
Factor two
-Going down the group , thenumer of intenrl eleectron shells also increase .
-Menaing there is more shiedling between nuclejus and the outer electorns .
-Both of these factors mens ,that theattration etwene te nucles nd outer eecorns decreases .
-Causing 1st ionsation energy to fall .
-ALTHOUGH , nuclear charg goes up dwont he grup it is oFFSET , by the two actrs i mentioned above .
CHECK THE GRAPH
-sucessive iosniation energy for the elemnt oxygen .
two things to nocie
FACTOR ONE
CHECK star one on grah too
-In the case of oxygne , we cns ee a gradual INCREASE , in ionsition energy ,a s we remove the first SI electrons .
-THIS IS BECASUE ,e ach time we remove an elecrrn ,t he remianing electrons in the outershella re pulled LSIGHTLY CLOSER ot the nucleus .
-Menaing htwre is a grter attraction , between the outer electrons and hte nucleus csuing ioinsiiton energy to GRADUALL INCREASE .
factor two
-check star two
-THere is a MASSIVE increase in ionsiationenergyw ehn we remvoe the sixth electron .
-can be eexplaiend b lookign t the electronsi no the ocygen atom
-The first six elecrons are removed in the SECOND ELECTRONS HELL .
-Once we have removed these elctron the 7TH ELECTRON IS REMOOVED FROM THE FIRST ELECTRON SHELL .
STAR TWO (2)
-compared to the econd electron shell , the first electron shell is clsoer to the neuclues and electrons int he first shell exoerience mcuh LESS HIELIDNG .
-Meaning electrons int he first shell , have a greater attaction to the nueclues comapred to the second hsell.
-EXPALINING why ionisaiton energy is MUCH GREATER for the 7th and 8th electrons ocmpared to the 6th .
EXAM - Could be asked to use first ionisation energy data to identify an element .
-First ionisation energyies for an elemnt in period 3 . (sShwoing not all jsut the first 6) .
Wokrout number of elecrons int he outer shell .
-STAR ONE - as you can see , ionisation enegry gradually increases up to the FOURTH ionisation .
-Form star two , massively increases whenw e get to ionisation number five .
-Telling us that the element has electrons in the outer hell .
-The fifth electron must hae been removed from an INTENRAL SHELL ,w hich is wh y its ionsition energy is MUCH GREATER .
As this electron hs foru electrons in the outer shell .
Period 4 group 4 the element is sillicon .
We find metals on the etside and non-metlas on the rightsid e.
-we find metallidus between them which are also known as SEMI METALS.
Lithium (2)
Because the lithiuma otms hve doanted thier outer electron we now describe them as CATIONS .
-tHE NEGATIVE delocalised electrons are strongly attrcted to postive cations by electrostatic attraction .
-This electrostatic attraction is metallic bdoning .
Period 2
LHS we ahve emtals LI and BE
Lithium ATOMS have three protons int he nucleus , and two electrons in the shell and 1 electron on t he outer shell .
-in metals m electrons in the outershella re DECOLAISED (in other words they are shared ).
What is the overall structure of a metal ?
GIANT METALLIC LATTICE
One key thing about giant metallic stucture
cations are fixed in place and nnot move
second thing about giant metallic structure
delocalsied electrons are free to move .
-As the deleoclaised electrons can move freely , this explains an important property of metals .
-MRTLS ARE GOOD CONDUCTORS OF ELECTRICITY ,W HEN THEYA RE BOTH SOLIDS AND LIQUIDS .
Imagine a voltage is applied to a metal .
-As youc an see , the deloclaised electrons are atracted to the psotive pole and move towards it .
-Int his case , the delocalised elecros are mobile charge carries , enabling metals to conduct electricity .
thirdmetallic strucutre
Aonther porepty i most metals hve relatively high melting and boilign points .
-THIS IS DUE TO THE STRENGTH OF THE METALLIC BOND .
rememebr - DELOCALISED ELECTRONS HAVE A STRONG ELECTROSTAIC ATTRACTION TO THE CATIONS .
–iT TAKES A LOT OF ENERGY TO OVERCOME THIS ATTRACTIONS SO METALS GENERaLY HAVE A HIGH Mleting point and boiling point .
Berryilium in period 2
Beryllium atoms have two outer electrons which are delocalised ,
-So in Be , the strength of the metallic bond is greater than LITHIUm .
-Therefore , beryllium has a higher melting and boiling point than lithium .
fourth thing about giant metallic strcutres
-They do not dissolve .
-When we dd a metal to water –. it reacts with the water rather than dissolving .
check grpah , showing the apporcimae melting points of the elemnts in period 2 .
Lithium and Berillyium have a high melting point due to their metallic bodning in their giant metalluc latice .
-Next Boron mettaaloid and non metal carbob , ahve a very high melting point becaue theyf ormg ian covalent strcutres .
Giant covalent strucutres
-Billions of atoms are joined by strong covalent bonds + together these atoms form giant covalent lattice .
-Takes a great deal o energy to break all the covalent bonds ina giant covalent lattice .
-Explaining why covalent strucuture have a high melting point nad oig point .
-boron forms a number of gian covalent strucutres .
Giant covalent strucutres of carbon
Carbon , is in group4 ,t ehre are 4 electrons in the outershell , carbon can covalently bond to four other carbon atoms .
-By doing this , the carbon atoms have formed a giant covalnet lattice .
-Whent his takes palce ,c ron has formed dimond .
What is the shape and bond angle of diamond ?
In diamond , toms are arranged in a tetrahedral strcutre with a bond angle of 109.5 degrees .
one key property of diamond
high melting point and boiling point , due to large amounts of energy required to break the covalent bonds .
second property of diamond
it does nto conduct lectricty , as every electron is in a covalent bodn .
-There are no delcolcised electrons to ct as charge carriers.
final property of diamond
-giant covalent lattices are insoluble .
-This is because , solvents cannot disrupt the largenumber o strong covalnet bonds .
-instead of forming 4 covalnet bonds i can form 3 and form graphiete .
bond angles and shape of graphite
graphite forms layers of planar hexagonal strctures and has a bond angle of 120 degrees .
-One electron from each carbon atom is delocalised can act as a mobile charge carrier.
-Because of these delcoalised electrons , graphite is a good conductor of electricity.
single layer of graphite is GRAPHENE
-due to its delocalsied electrons , graphene is also a good conducotr of electicity.
check star oen of graph
-after carbon , the metling points of the elemnts in period 2 , drop very sharply .
n2 , o2 , f2 , all consits of diaomtic moelcules and are gases a rtp .
Ne -> is a noble gas consisiting of indivual neon atom .
if we cool these elements down to solid form ,t hey form a simple molecular lattice , with wek inermolecular forces between the moelcules .
-These weak inermolecular forces don’t requrie a lto of energy to break ,w hich is why these elemnts have low mp nd bp .
-so the changes in melting points cross period 2 is due to strcuutre and bonding .
A similar pattern occurs in period 3
Giant metallic strucutre , giant covalent and simple moelcular
phosphour is p4 and sulfur is s8 which are solids at rtp .
First five elements in group 2 check sheet , what are they referred to as ?
Elements in group 2 are referred to
As the alkaline earth metals
