Module 3.1 The perodic table Flashcards
in the early 1800s what where the only two ways to categorise elements
- by their physical and chemical properties
- by their relative atomic mass
explain Dobereiner’s triads
he group elements with similar characteristics in threes and called them triads.
explain the law of octaves
Newlands order elements by mass and found similar elements appeared at regular intervals every 8th element was similar.
Mendeleev produced the first accepted version. what did his table contain
arranged elements by atomic masses.
left gaps where the next element didn’t seemed to fit.
he predicted the properties of undiscovered elements.
what do all elements in a period have in common
they all have the same number of electron shells (although not sub-shells)
period 1 has 1 electron shell and so on.
repeating trends in chemical and physical properties across the period due to this.
the trends that elements share in periods are known as
periodicity
what do all elements in the same group have in common
they all have the same number of electrons in their outer shell.
this causes them to also have similar CHEMICAL properties.
what does the group number tell you?
the number of electrons in the outer shell
s block elements contain which groups
groups 1 and 2
what is the outer shell electron configuration of elements in the s block
S(1) or S(2)
e.g Mg is 1s(2) 2s(2) 2p(6) 3s(2)
Li is 1s(2) 2s(2)
what part of the perodic table is the d block
the transition metals
what is the electron configoration of d block elements
outer shell is always a d sub shell
e.g cobalt: 1s(2) 2s(2) 2p(6) 3s(2) 3p(6) 3d(7) 4s(2)
(even though 4s fills first and so the last sub shell is 3d it is not written this way)
the p block contain which groups of elements
groups 3-7 and 0
what is the outer shell electron configurations of elements in the p block
from s(1)p(1) to s(2)p(6) e.g Cl: 1s(2) 2s(2) 2p(6) 3s(2) 3p(6)
period 1 can have what outer sub shell configeration
up to 1s(2)
period 2 can have what outer sub shell configeration
up to 2s(2) 2p(6)
period 3 can have what outer sub shell configeration
up to 3s(2) 3p(6)
ionisation is
the removal of one or more electrons
the first ionisation energy is
the energy needed to remove 1 mole of electrons from 1 mole of gaseous atoms.
you put energy in to ionise an atom so it is an
endothermic process
give the equation of the first ionisation of oxygen
O(g) –> O+(g) + e-
the lower the ionisation energy
the easier it is to form an ion
factors affecting ionisation energy are (3)
- NUCLEAR CHARGE
- ATOMIC RADIUS
- SHIELDING
nuclear charge affects ionisation energy how?
the more protons there are in nucleus the more ve+ charged the nucleus is and the STRONGER THE FORCE OF ATTRACTION for the electrons
atomic radius affects ionisation energy how?
attraction falls off very rapidly with distance. an electron close to the nucleus will be much more strongly attracted than one further away.
shielding affects ionisation energy how?
as the no. of e- beteween outer e- and the nucleus increases the outer e- feel less attraction towards the nuclear charge.
a high ionisation energy means there is a
strong attraction between the e- and the nucleus so more energy is needed to overcome the attraction and remove the electron.
how does ionisation energy change as you go down a group
ionisation energy usually falls i.e it gets esier to remove outer electrons
ionisation energy decreases down a group because (2)
- ATOMIC RADIUS elements further down have more
electron shells. increasing atomic radius so outer
electrons are further away from nucleus - SHIELDING the extra inner shells shield the outer
electrons from the attraction of nucleus
-although protons ve+ charge increases so does the
electrons ve- charge so there is no effect
how does ionisation energy change as you go across a period
ionisation energy increases as you go across a period
why does ionisation generally increase as you go across a period (2)
- NUCLEAR CHARGE number of protons is increasing. as
ve+ of nucleus increases electrons are pulled closer
reducing ATOMIC RADIUS - extra electrons gained are added to the outer energy
level so don’t provide extra shielding effect
what are the 2 exceptions to the trends in ionisation energy on the period table?
- the drop between groups 2 and 3
- the drop between groups 5 and 6
why is there a drop in ionisation energy between groups 2 and 3
SUB-SHELL STRUCTURE
- outer electron in group 3 is in a p orbital rather than s
- p orbital has slightly higher energy than s in the same shell
- so electron is found further away from the nucleus
- these factors override the effects of the increasing nuclear charge resulting in ionisation energy dropping slightly
why is there a drop in ionisation energy between groups 5 and 6?
p ORBITAL REPULSION
- in group 5 elements the electron is being removed from a singly occupied orbital
- in group 6 elements the electron is being removed from an orbital containing 2 e-
- the repulsion between the 2 electrons means that the e- is easier to remove from shared orbitals.
what does successive ionisation energies involve
involves the removal of additional electrons
the equation for the 2nd ionisation of oxygen is:
O+(g) –> O2+(g) + e-
successive ionisation energies can show
the shell structure of an element
how does successive ionisation energies show shell structure
- within each shell, successive ionisation energies will increase as you are removing e- from increasingly +ve ion and there is less repulsion amongst remaining electrons
- big jumps in ionisation energy happen when a new shell is broken into as electron is being removed in a shell closer to the nucleus.
- this shows shells.
successive ionisation energies can also predict
electronic structure of an element.
by counting the no, of electrons removed before each big jump tells u how many e- are in each shell.
diamond, graphite and graphene are…
giant covalent lattices
what are giant covalent lattices
- huge networks of covalently bonded atoms.
- carbon atoms can form this type of structure because they can each form 4 strong covalent bonds
what are different forms of the same element in the same state called
allotropes
name and explain the properties of diamond (5)
- very high melting point due to strong covalent bonds
- diamond is the strongest known substance due to giant covalent lattice tetrahedral shape each carbon bonded to 4 others
- good thermal conductor. (vibrations travel easily)
- can’t conduct electricity (all outer electrons are held in localised bonds.
- it wont solved in any solvent
name a element with very similar properties to carbon and what it can form
silicon
- in same periodic group
- also forms crystal lattice with similar properties to carbon
- can form 4 strong covalent bonds
name and explain the properties of graphite (4)
- feels slippery:
weak forces between layers in graphite are easily
broken so that sheets can slide over each other. - conduct electricity:
delocalised electrons aren’t attached to any particular
carbon and are free to move along sheets. - very high melting point:
because of strong covalent bonds in hexagonal sheets - insoluble:
covalent bonds are too strong to break
describe the structure of graphene
is a sheet of carbon atoms joined in hexagons.
the sheet is one atom thick making it 2-dimesonal
describe and explain the properties of graphene (3)
- conducts electricity:
de-localised electrons free to move along the sheet. the single layer allows quicker movement above and below sheet making it the best known conductor
-extremely strong:
de-localised electrons strength covalent bonds
-transparent and light
due to it only being a single layer
metal can have giant structures called
giant metallic lattices structures.
describe how giant metallic lattices structures form (metallic bonding):
- e- in outer shell are delocalised leaving a +ve metal cation
- metal cations are electrostatically attracted to the delocalised e-.. they form a lattice of closely packed cations in a sea of delocalised electrons.
describe and explain the properties of metals in terms of metallic bonding (5)
- MELTING POINT effect by no. of delocalised e- per atom
the more there are the stronger the bonding and higher the melting point. the size of metal ion and lattice structure also have an effect. - MALLEABLE AND DUCTILE:
no bonds holding specific ions together they can slide past each other.
-GOOD THERMAL CONDUCTORS
delocalised e- can pass kinetic energy to each other
-GOOD ELECTRICAL CONDUCTORS
delocalised electrons can move and carry current
-INSOLUBLE
except in liquid metals, because of the strength of metallic bonds
what factors affect melting and boiling points of simple molecular structures
Melting and boiling points depend on strength of induced dipole dipole forces
the more atoms their are the stronger the induced dipole- dipole forces.
noble gases have very low melting and boiling points as they exist as individual atoms resulting in very weak induced dipole-dipole interactions.
summaries properties ionic bonding result in:
- high melting and boiling points solid at STP does not conduct electricity as solid conducts electricity as liquid not soluble in water
summaries properties simple molecular (covalent) bonding results in:
low melting and boiling points (only have london forces
at STP usually liquid or gas occasionally solid
does not conduct electricity as a solid or liquid
solubility depends on how polarised the molecule is
summaries properties of giant covalent lattices
high melting and boiling points
solid at STP
does not conduct electricity when solid apart from graphite and graphene
does not conduct as liquid (not normally in this state)
is not soluble in water
summaries properties of metalic bonding
high melting and boiling points
solid at STP
conducts electricity as solid and liquid (delocalised e-)
are not soluble in water
going across the period how does the melting and boiling points change for metals (Li, Be, Na, Mg, Al)eland why
melting and boiling points increases across a period
because the metallic bonds get stronger as the ionic radius decreases and the number of delocalised electrons increases.
elements with giant covalent lattice structure (C and Si) have strong ________ so have _____ melting and boiling points.
elements withe giant covalent lattice structure have strong covalent bonds so have high melting and boiling points.
elements that form simple molecular structures only have weak ____________ to overcome between molecules so have ___ melting and boiling points.
elements that form simple molecular structures only have weak intermolecular forces to overcome between molecules so have low melting and boiling points
noble gases have the ________ melting and boiling points in their periods because ___
noble gases have the lowest melting and boiling points in their periods because they are held together by the weakest forces
group 2 elements form __ ions because
group 2 elements form 2+ ions because they have two e- in their outer shell s(2)
so they lose two outer e- to form 2+ ions
how does reactivity change as you go down group 2 and why
reactivity increases down group 2
- ionisation energies decreases because:
1. increasing atomic radius
2. shielding effect - easier to lose electrons to form +ve cations
when group 2 elements react they are
oxidised
from state of 0 to +2 forming M2+ ions
M –> M2+ +2e-
0 +2
group 2 metals + water —>
group 2 metals + water –> metal hydroxide + hydrogen
M + 2H2O —> M(OH)2 + H2
group 2 metals + oxygen —>
group 2 metals + oxygen --> metaloxides
(they burn in oxygen)
2M + O2 ---> 2MO
0 +2
0 -2group 2 metals + acid –>
group 2 metals + acid(dilute) —-> salt + hydrogen
M + 2HCl –> MCl2 + H2
the group 2 metals are known as
the alkaline earth metals
group 2 oxides and hydroxides are what:
they are bases
most are also soluble in water, so are also alkalis
group 2 oxides + water —>
metal hydroxides
which dissolve.
hydroxide ion OH- make the solution strongly alkaline
what group 2 oxide is the exepetion
magnesium oxide
only reacts slowly and the hydroxide it forms is not very soluble.
how does the strength of the alkali solution group 2 oxides make as you go down the group
as you go down the group the more strongly alkaline solution is. because they hydroxides get more soluble.
group 2 compounds are often used to
neutralise acidity
what group 2 hydroxide is used in agriculture to neutralise acidic soils
calcium hydroxide (slaked lime, Ca(OH)2 )
what 2 group 2 compounds are commonly used in indigestion tablets as antacids
magnesium hydroxide Mg(OH)2
calcium carbonate CaCO3
what is the equation for neutralisation
H+ + OH- —> H2O
neutralisation equation for magnesium hydroxide
Mg(OH)2 + 2HCl —-> 2H2O + MgCl
give fluorine’s: formula, colour, physical state at 20oc and electronic structure
formula: F2
colour: pale yellow
sate: gas
1s(2) 2s(2) 2p(5)
give chlorine’s: formula, colour, physical stat at 20oc and electronic structure
formula: Cl2
colour: green
state: gas
1s(2) 2s(2) 2p(6) 3s(2) 3p(5)
give bromine’s: formula, colour, physical state at 20oc and electronic structure
formula: I2
colour: red-brown
state: liquid
1s(2) 2s(2) 2p(6) 3s(2) 3p(6) 3d(10) 4s(2) 4p(5)
give Iodine’s: formula, colour, physical state at 20oc and electronic structure
formula: I2
colour: grey
state: solid
1s(2) 2s(2) 2p(6) 3s(2) 3p(6) 3d(10) 4s(2) 4p(6) 4d(10) 5s(2) 5p(5)
halogens exist as _______ molecules
halogens exist as diatomic molecules
what happens to halogen boiling and melting points as you go down the group
their boiling and melting points increase
why does halogen boiling and melting points increases as you down the group?
- due to increasing strength of the London forces as the size and relative mass of the atoms increases
what happens to the physical state of halogens as you go down the group
they halogens become less volatile as you go down the group.
what happens to halogen reactivity as you go down the group
halogens get less reactive as you go down the group
why do halogens get less reactive as you go down the group?
- as you go down atomic radii increases so outer e- are further from the nucleus.
- shielding increases as there are more inner electrons
- makes it harder for atoms to attract the electron they need to form an ion, so the larger atoms are less reactive
how do halogens react?
halogens react by gaining an electron in their outer shell to form 1- ions.
this means they are reduced and are oxidising agents.
what is another way to say that halogens get less reactive as you go down the group
halogens become less oxidising as you go down the group.
how do halogen displacement reactions work
halogens with a larger oxidising strength displace halogens with lower oxidising strengths.
e.g fluorine will replace bromine.
write the full and ionic equation with oxidation numbers to show what happens when bromine water displaces potassium iodine
full: Br2 + 2KI —> 2KBr + I2
ionic: Br2 + 2I- —-> 2Br- + I2
Br 0 -1
I -1 0
bromine displaces the iodine ions ________ them
bromine displaces the iodine ions oxidising them
chlorine will displace what halogens
chlorine will displace bromide and iodide
bromine will displace what halogens
bromine will displace iodide
iodine will displace what halogens
iodine will not displace any halogens
fluorine will displace what halogens
fluorine will displace chloride, bromide and iodide
what solution can be used to test for halogens
silver nitrate solution
how do you test for halogens
- first add dilute nitric acid to remove ions that might interfere
- then add silver nitrate solution (AgNO3)
- if halogen present a precipitate will form (silverhalide)
- identify with colour
- add ammonia solution do see how well the siverhalide dissolves to help identity
testing for chlorine with silver nitrate what will form
- a white precipitate
- dissolves in dilute NH3
testing for bromine with silver nitrate what will form
- cream precipitate
- dissolves in conc. NH3
testing for iodine with silver nitrate what will form
- yellow precipitate
- insoluble in conc. NH3
what is the ionic equation when a halide ion reacts with silver nitrate
Ag+ + X- —> AgX
halogens undergo ___________ with alkalis
halogens undergo disproportionation with alkalis
in disporportionation reactions what happens
something is simultaneously oxidised and reduced
give the full and ionic equation with oxidation numbers for when a halogen reacts with sodium hydroxide NaOH
X2 + 2NaOH —> NaXO + NaX + H2O
X2 + 2OH —> XO- + X- + H2O
0 +1 -1
what are the 3 different oxidation states chlorine can be at
- chloride Cl- -1
- chlorine Cl2 0
- chlorate ClO- +1
all halogens can undergo disportionation reactions apart from…
fluorine
chlorine and sodium hydroxide make what
chlorine and sodium hydroxide make bleach
what is common household bleach
sodium chlorate(I) solution NaClO
the equation for when chlorine and sodium hydroxide react to make bleach as well as oxidation numbers of chlorine
2NaOH + Cl2 —-> NaCLO + NaCl + H2O
0 +1 -1
write the equation for when chlorine is mixed with water
Cl2 + H2O HCl + HClO
0 -1 +1
chloric (I) acid
chlorine undergoes _________ when mixed with water
chlorine undergoes disproportionation reaction with water
why is chlorine / compound with chlorate (I) ions mixed with drinking water
to kill bacteria to make water safe to drink / swim in
write the equation for when acid ionises to make chlorate(I) ions
HClO + H2O ClO- + H3O+
why is chlorine an important part of water treatment (3):
- it kills disease causing microorganisms
- some chlorine remains in the water and prevents reinfection further down the supply
- it prevents growth of algae eliminating bad tastes, smells and removes discolouration caused by organic compounds
what are the risks of using chlorine in water (3)
- chlorine gas irritates respiratory system.
- liquid chlorine causes severe chemical burns so accidents involving chlorine are serious, fatal.
- chlorine reacts with organic compounds in water forming chlorinated hydrocarbons many are carcinogenic.
what are the alternatives to chlorine (2)
- ozone (O3) a strong oxidsing agent kills microoganisms expensive and has a short half life so treatment is not permanent
- uv light: damage microorganisms DNA, ineffective in cloudy water wont stop later contamination.
how do you test for carbonates (CO32-)
- add dilute acid if present then carbon dioxide will be released
- test for carbon dioxide using lime water
what is the equation for the reaction between carbonate ion and dilute acid
CO3(2-) + 2H+ –> CO2 + H2O
how do you test for sulfates?
- add dilute HCl followed by barium chloride solution, BaCl2
- barium sulfate forms a white precipitate
what is the equation for sulfate tests
Ba2+ + SO4(2-) —> BaSO4
how do you test for halides
- add nitric acid, then add silver nitrate
- add ammonia to see solubility
how do you test for ammonium compounds
- ammonia gas NH3 is alkaline. damp red litmus paper will turn blue
- to test for ammonium ions NH4+ add sodium hydroxide NaOH and warm the mixture. test for ammonia given off
what is the equation for testing for ammonium ions
NH4+ + OH- —-> NH3 + H20
what order do you test for substances in
- test for carbonates
- test for sulfates
- test for halides
