1.6 the periodic table Flashcards
how are elements arranged on the periodic table?
according to atomic number
(not mass number)
why is (e.g Mg in the s-block) of the periodic table?
its outer electron is in a s-orbital
e.g 1s^2 2s^2 2p^6 3s^2
what are the 4 blocks in the periodic table?
s, p, d and f block
how can the gain and loss of electrons be shown by?
half equations
what is oxidation?
the loss of electrons
what does a half equation look like for oxidation?
Fe2+ —> Fe3+ + e-
(electron is on the right hand side)
what is reduction?
the gain of electrons
what does a half equation look like for reduction?
MnO4 - + 8H+ + 5e- —> Mn2+ + 4H2O
(electron is on the left hand side)
what is a redox reaction?
a reaction that involves both oxidation and reduction
(involves the transfer of electrons)
can electrons be created or destroyed?
no
they can only be transferred from one species to another
what does Oil A Rig stand for?
oxidising agent is gain
reducing agent is loss
what is the half equation for the oxidation of chlorine ions to chlorine gas?
2Cl - —> Cl2 + 2e-
what is the half equation for the reduction of copper (II) ions to copper metal?
Cu2+ + 2e- —> Cu
what is the half equation from MnO4 - —> Mn2+?
MnO4 - —> Mn2+
oxidation numbers = +7 -2 (-8) —> +2
5e- + MnO4 - + 8H+ —> Mn2+ + 4H2O
(to double check, the reactants’ overall oxidation number should equal the products’ overall oxidation number)
when using half equations to find the overall equations, do you write the electrons into the equation?
no
they are eliminated (because they are the same on both sides)
what is the flame test colour for lithium ions?
red
what is the flame test colour for sodium ions?
yellow-orange
what is the flame test colour for potassium ions?
lilac
what is the flame test colour for calcium ions?
brick red
what is the flame test colour for strontium ions?
crimson
what is the flame test colour for barium ions?
apple green
what is the flame test colour for magnesium ions?
no visible colour
what are flame tests used for?
used to distinguish the type of metal ion present in a sample
what do the silver nitrate tests do?
distinguish which halide ions are present in a sample
what is the colour of the precipitate in the silver nitrate test for chloride ions?
white
what is the colour of the precipitate in the silver nitrate test for bromide ions?
cream
what is the colour of the precipitate in the silver nitrate test for iodide ions?
yellow
what test can you do to distinguish between chloride ions and bromide ions if the silver nitrate test precipitates are too close in colour?
add dilute or aqueous ammonia (NH3)
Cl- is more soluble than Br- or I- so will dissolve in dilute ammonia compared to Br- which won’t
the solubility of group 7 silver halides ____ down the group?
decreases
what is the ionic equation for a silver halide formation?
e.g Ag + (aq) + Cl- (aq) —> AgCl (s)
what colour is iodine when solid? liquid? a gas?
- grey solid
- brown liquid
- purple gas
the solubility of group 2 sulfates _____ down group 2?
decreases
the solubility of group 2 hydroxides _____ down group 2?
increases
the solubility of group 2 carbonates _____ down group 2?
stay the same
(all group 2 carbonates are insolublr white precipitates)
what is the observation of group 2 ions reacting with sulfate ions (SO4 2-)?
(magnesium ions, calcium ions, barium ions)
magnesium ions = soluble
calcium ions = faint white ppt
barium ions = heavy/thick white ppt
what is the observation of group 2 ions reacting with hydroxide ions (OH -)?
(magnesium ions, calcium ions, barium ions)
magnesium ions = white ppt
calcium ions = faint white ppt
barium ions = soluble
what is the observation of group 2 ions reacting with carbonate ions (CO3 2-)?
(magnesium ions, calcium ions, barium ions)
magnesium ions = white ppt
calcium ions = white ppt
barium ions = white ppt
are all metal nitrates soluble or insoluble?
soluble
are all group 1 sulfates, hydroxides, carbonares and halidrs soluble or insoluble?
soluble
are all group 2 halides insoluble or soluble?
soluble
what chemicals are soluble?
- all metal nitrates
- all group 1 sulfates, hydroxides, carbonates and halides
- all group 2 halides
in an exam, when asked to mix together two chemicals to get a white ppt, be careful not to give chemicals which ate themselves insoluble
also always give a chemical rather than an ion as a reagent
what group 2 metals react with steam to produce the group 2 oxide and hydrogen gas?
beryllium and magnesium
what is an equation for beryllium reacting with steam?
Be (s) + H2O (g) —> BeO (s) + H2
what group 2 metals react with (cold) water to produce the corresponding metal hydroxide and hydrogen gas?
calcium, strontium and barium
what is an equation for calcium reacting with cold water?
Ca(s) + 2H2O (l) —> Ca(OH)2 (s) + H2 (g)
why do the reactions become easier as you go down group 2?
as it becomes easier to form the 2+ ion due to a decrease in ionisation energy down the group
when is a compound described as thermally stable?
if it requires a lot of heat energy to be broken down or decomposed
what is a combustion reaction?
when a compoubre reacts with oxygen
what do the group 2 metal carbonates thermally decompose to form?
the metal oxide and carbon dioxide gas
the group 2 metal carbonates become ____ thermally stable as you go down thr group?
more
what does it mean that the group 2 metal carbonates become more thermally stable as you go down the group?
they need to be heated to higher temperatutes to thermally decompose (harder to thermally decompose)
what do the group 2 metal hydroxides thermally decompose to form?
the metal oxide and water (steam)
the group 2 metal hydroxides become ____ thermally stable as you go down the group?
more
(i.e they need to be heated to higher temperatures to thermally decompose)
what is a base?
a proton (H+) acceptor
(pulls H+ towards itself)
what is a basic oxide?
one that dissolves in water to produce a compound that is able to accept protons
what do group 1 and 2 oxides react with water to produce?
a metal hydroxide (as the only product)
metal oxide + water —> metal hydroxide
what is the equation for sodium oxide reacting with water?
Na2O + H2O —> 2NaOH
OH- —> high pH
rank barium hydroxide, magnesium hydroxide and sodium hydroxide in order of least soluble to most soluble
Mg(OH)2 —> insoluble
Na(OH)
Ba(OH)2 —> most OH-
are metal oxides (group 1 and 2) basic?
yes as they react with water to producr a solution of hydroxide ions
generally group 1 oxides/hydroxides are (stronger/weaker) bases than group 2 metal oxides and hydroxides
stronger
group 1 and 2 carbonates are (strong/weak) bases?
weak
what do all halogens react with sodium to produce?
sodium halides (a white salt)
(the sodium is oxidised and the halogens are reduced)
what is an equation for the reaction between sodium and fluorine?
2Na + F2 —> 2NaF
oxidation numbers = 0 + 0 —> +1 -1
what do chlorine and bromine react with iron to produce?
iron (III) chloride and iron (III) bromide
what does iodine react with iron wool to produce?
iron (II) iodide
for the reactions of the halogens with sodium and iron, does the reactivity increase or decrease down the group?
decrease
what is an equation for the reaction between iron and chlorine(or bromine)?
2Fe + 3Cl2 —> 2FeCl3
what is an equation for the reaction between iron and iodine?
Fe + I2 —> FeI2
the oxidising power of the halogens ____ as you go up group 7?
increases as you go up group 7
what is the best oxidising agent in group 7?
fluorine
why is fluorine the best oxidising agent?
- has the least amount of shielding compared to other halogens as it’s a smaller molecule
- so the strongest electrostatic attraction between the positive fluorine nucleus and the outermost electron
- so able to attract and gain other electrons -ie becoming reduced whilst also causing the molecule/ion that it has taken these electrons from to be oxidised
what does it mean that fluorine is the best oxidising agent?
therefore will cause oxidation and itself become reduced
(gain electrons)
if fluorine is the best oxidising agent, what is the worst reducing halide ion of the group 7 halide ions?
fluorine
why do displacement reactions happen?
a more oxidising halogen will displace a more reducing halide from its salt
are ‘displacent reactions’ redox reactions?
yes
write a balanced symbol equation, identify the oxidising and reducing agents and write an ionic equation for the reaction between sodium bromide and fluorine
2NaBr + F2 —> 2NaF + Br2
+1 -1 + 0 —> +1 -1 + 0
Br oxidised
F2 reduced
2Br - + F2 —> 2F- + Br2
what are disproportionation reactions?
a redox reaction where one species becomes both oxidized and reduced
what is the general trends in ionisation energy in the periodic table?
- 1st IE generally decrease down a group (due to an increased shielding effect from inner shells and also due to an increased distance from the outer electron to the positive nucleus of the atom)
- 1st IE generally increase across a period (due to an increase in the nuclear charge with no extra shielding which also increases the effective nuclear charge, binding electrons more strongly)
what is the general trends in electronegativity in the periodic table? why?
- electronegativity generally decreases down a group (due to bonding electrons being further away from the positive nucleus as the atom gets bigger in size)
- generally increases across a period (due to an increase in the nuclear charge with no extra shielding which also increases the effective nuclear charge, which binds the electrons more strongly)
what is the general trends in melting temperatures across a period in the periodic table?
- across a period, the type of structure changes: from metallic, to simple covalent, to simple molecular, to atomic
so, the metallic and giant covalent structures will have much higher melting points than the other structure types
what is the general trends in melting temperatures down a group in the periodic table?
- for group 1 and 2 metals, the mp will generally decrease down a group (bc there is a lower charge density on the metal ion in the metallic bond as there is the same charge in a larger area as atom size increases down a group. so less attraction resulting in lower mp)
- for non-metals, the melting point generally increases (bc there are stronger VdW forces between molecules due to an increase in molecule size as you go down the group due to an increased temporary dipole size)
what is the general trends in reactivity in the periodic table? (down group 1 and 2) why?
- group 1&2 metals become more reactive down the group
the ease of cation formation becomes easier to do on going down a group due to an increased distance from the nucleus and the effect of shielding from inner shells. this makes the metald more willing to react in order to form their ions, which results in an increase ib reactivity
what is the general trends in atomic radii (distance brtween centre of nucleus and the outer electron shell) in the periodic table?
- increases down a group due to an increase in shells
- decrease across a period due to the increased nuclear charge, which binds the outer electron more strongly to the nuclear and effectively ‘pulls’ them towards the nuclei - resulting in a shortening distancr between thr nucleus and outer electron shell
what is the use of chlorine in water?
how is it done?
to kill bacteria in order for it to be safe to drink
- chlorine gas is bubbled through water to kill microorganisms
- without doing this step, water can be dangerous to drink and some bacteria such as cholera would thrive and kill
(sterilisation)
what is the use of fluoride in water?
- strengthening tooth enamel
- this is the process of adding fluoride salt (not fluorine) to water in order to promote better dental hygiene
- prevent tooth decay
what are some arguments against adding fluoride to water?
- too much fluoride can cause dental fluorosis
- form of mass medication
- fluoride is already in toothpaste, mouthwash etc
- more money to fluoridate water
what are some arguments for adding fluoride to water?
- at the correct dose, has been proven to improve dental hygiene
- long term better tooth health will result in less money spent on dental issues in UK NHS budget
what is the main difference between adding chlorine to water and adding fluoride?
- adding chloride to water is essential to avoid becoming affected
- adding fluoride is only to enhance health
what is gravimetric analysis?
the determination of identities or concentrations of substances by using its mass
what is the process of gravimetric analysis?
- add excess amounts of (sulfuric acid) to (barium chloride)
- the white ppt formed can be collected by filtering the solution
- test the filtrate (liquid) by adding more (sulfuric acid)
- re-filter if more ppt is formed
- wash the ppt on the filter paper to remove any soluble impurities
- dry ppt in warm oven below melting point of substance in order to evaporate off any water
- weigh ppt and perform any relevane calculation
(ensure every ion that you are trying to precipitate is precipitated - which is whu we test the filtrate. or you are not accounting for ions potentially left in the solution which is going to make calculations wrong)
what is the filtrate?
the liquid that runs through the filter
why do you wash the ppt in gravimetric analysis?
to remove any soluble impurities
why do you dry the ppt in a warm oven below the melting point of the substance in gravimetric analysis?
to evaportate off any water
in gravimetric analysis, when do you stop drying the ppt (below melting point)?
until constant mass
what does the group number correspond to?
the number of electrons in the outer shell
what are oxidising agents?
a species that accepts electrons, thereby helping oxidation. it becomes reduced itself in the process
e.g 2Na + Br2 -> 2NaBr
0 + 0 —> +1 -1
Br2 is the oxidising agent
what are reducing agents?
a species that donates electrons, thereby helping reduction. it becomes oxidised itself in the process
e.g 2Na + Br2 -> 2NaBr
0 + 0 —> +1 -1
Na is the reducing agent
what do group 1 and group 2 form?
basic oxides
group 1 - alkali metals
group 2 - alkaline earth metals
is hydrogen a group 1 metal?
no because even though it has 1 electron in its outer shell, it is a non-metal and doesn’t follow the trends of reactivity of the rest of the group
how do you carry out a flame test?
- dip a wire loop into concentratrd hydrochloric acid and then hold in the flame of a bunsen burner to remve any contaminants
- then dip the loop in the compound to be tested and hold again in the blue flame. observe any colour shown
what is formed when the s-block (group 1 + 2) comes into contact with oxygen or air?
oxides are formed
how are group 1 metals stored to prevent their reaction with oxygen?
they are stored under oil
what is the general equation for group 1 metals reacted with oxygen/air?
4M + O2 —> 2M2O
where M = Li, Na or K
what is the general equation for group 2 metals reacted with oxygen/air?
2M + O2 —> 2MO
where M = Mg, Ca, Sr or Ba
what is usually formed in the reaction between group 1 + 2 elements and water?
hydroxides
(hydrogen is also released, which means effervescing is observed)
what is the general equation for group 1 reactions with water?
2M + 2H2O —> 2MOH + H2
where M = Li, Na or K
(for group 1, the metals react more vigorously as you go down the group)
what happens with the group 2 metals when theu react with water? (beryllium, magnesium, calcium, strontium and barium)
- beryllium and magnesium will react with steam to form an oxide + hydrogen gas
- calcium, strontium and barium will react with water to form a hydroxide + hydrogen gas
when group 2 carbonates are heated, what do they undergo? what do they produce?
- they undergo thermal decomposition
- to produce an oxide and carbon dioxide gas
e.g CaCO3 —> CaO + CO2
when metal hydroxides are heated, what do they undergo? what do they produce?
- thermal decomposition
- to form an oxide and water
e.g Ba(OH)2 —> BaO + H2O
does the thermal stability of metal carbonates increase or decrease down the group?
increase
does the thermal stability of metal hydroxides increase or decrease down the group?
increase
does the solubility of group 2 hydroxides increase or decrease down the group?
increase
does the solubility of group 2 sulfates increase or decrease down the group?
decrease
are group 1 bases stronger than group 2 bases?
yes
what is the strength of a base measured by?
how readily the base will dissociate into ions completely in solution
what state and colour is fluorine at room temperature?
pale green gas
what state and colour is chlorine at room temperature?
yellow green gas
what state and colour is bromine at room temperature?
brown liquid
what state and colour is iodine at room temperature?
grey solid
(which sublimes on heating to form a purple vapour)
reactivity, oxidising power and volatility (increase/decrease) down the group?
decreases
why does the volatility (tendency to form a gas) and the melting point of the halogens decrease down the group?
because the intermolecular forces get stronger as the atom gets bigger
what do you see in all the reactions between the halogens and sodium?
a bright orange flame (as sodium ignites)
and a white solid halide will be produced
what is the general equation for thr reaction between the halogens and sodium?
2Na + X2 —> 2NaX
where X = any halide
what is seen in the reaction between the halogens and iron?
- iron wool will glow and then burn in halogen vapour to form iron halides which appear as a brown gas
due to the reaction between the halogens and sodium starting less readily as you go down the group, what can you do to help start the reaction?
the halide vapour may need heating to help start the reaction
what is the general equation for the reaction between the halogens and iron? what is the formula for iodine (the exception)?
2Fe + 3X2 —> 2FeX3
where X = fluorine, bromine or chlorine
Fe + I2 —> FeI2
as it’s much less reactive it needs to be heated quite strongly and will only form iron (II) iodide
volatile definition
how easily a substance is promoted into the gas phase (ie is vaporised)
as you go down group 7, the volatility of the halogens (increases/decreases)?
decreases
why does the volatility of the halogens decrease as you go down group 7?
- bc the strength of thr VdW forces increases on going down the group due to an increase in molecule size
- this gives the halogen molecules larger dipoles, resulting in stronger VdW forces between molecules
- hence, more energy is required to break the IMF between halogen molecules and hence put them into the gas phase
(at RTP, the energy in thr room is enough to break these IMF forces in bromine and chlorine but not iodine)
what are some everyday uses of strong bases (e.g group 1 metal hydroxides)?
- often used in cleaning products
- bleach and oven cleaners consist of a strong concentration of sodium hydroxide
what are some everyday uses of weak bases (e.g group 2 metal hydroxides)?
- e.g magnesium hydroxide is used in ondigestion or antacid remedies
- the idea is that excess stomach acid can be neutralised by the base to create a salt and water in your stomach
- stronger bases such as calcium and barium hydroxide which are also group 2 hydroxides cannot be used as they are too soluble and hence have a higher amounts of hydroxide ions- this woulf harm your stomach lining
what do bleach and oven cleaner consists of?
a strong concentration of sodium hydroxide
(group 1 metal hydroxide)
how is e.g magenisum chloride used in everyday uses? (group 2 metal hydroxide)
used in indigestion or antacid remedies
why is magnesium chloride (a group 2 metal hydroxide) used in indigestion or antacid remedies?
the excess stomach acid can be neutralised by the base to create a salt and water in your stomach
why can’t calcium and barium hydroxide (also group 2 hydroxides) be used in indigestion or antacid remedies?
bc theu are too soluble and hence have higher amounts of hydroxide ions which would harm your stomach lining
what are some everyday uses of group 2 carbonates?
- also used in antacid tablets such as magnesium and calcium carbonate as they are weaker bases and would not harm the stomach lining
what do all elements along a period have?
the same numver of electron shells
why has silicon got a much higher boiling point compared to sodium, magnesium and aluminium? (period 3)
silicon is macromolecular meaning it has a very strong covalent structure.
they require a lot of energy to break, giving it a very high melting point
what do group 2 ions react with OH- ions to form?
hydroxides
what do group 2 element ions react with SO4 2- to form?
hydroxides
what makes barium sulfate useful as a medical tracer (barium meals) that allows internal tissues and organs to be images?
its insolubility
barium sulfate is toxic if it enters the bloodstream, however since it’s insoluble, it cannot be absorbed into the blood, which makes it safe to use in the body
what is the test for sulfate ions?
barium chloride
forms a white ppt
what do halogens react with metals to produce?
salts such as sodium chloride
do the halogens act as good oxidising agents or reducing agents? why?
they act as good oxidising agents as they accept electrons from the species being oxidised and are reduced as a result
(the oxidising power decreases down the group as their ability to attract electrins decreases due to shielding and a greater atomic radius)
do halide ions act as good oxidising agents or reducing agents? why?
they are good reducing agents as they donate electrons to the species being reduced and are themselves oxidised
(the reducing power increases down the group as electrons are easier to lose from larger ions since there is a reduced nuclear attraction due to shielding and a larger atomic radius)
how does adding chlorine to water kill bacteria?
when the chlorine reacts with cold water, chlorate (I) ions (ClO-) are produced which are very good at killing bacteria, helping to treat the water and make it safe to drink
how can soluble salts be formed?
by reacting acids with insoluble or soluble bases
how can a soluble salt be separated from a solution?
by crystallisation or evaporation
how can an insoluble salt be formed?
by a precipitation reaction
why do we carry out several titrations and then calculate a mean?
to obtain a more reliable value
why do we carry out a rough titration first?
- so that a certain volume of acid can be added quickly before adding drop by drop
- / to save time before doing accurate titrations
- / to give a rough idea of the end point
what is the name of the chlorine-containing compound in bleach?
sodium chlorate (1)
ewan and gwyneth are provided with a white solid that they believe to be sodium bromide or sodium iodide.
they dissolve the solid in water to make a solution. explain what occurs when an ionic solid such as sodium bromide dissolves in water
- sodium ions surrounded by δ- on oxygen atoms of water
- bromide ions surrounded by δ+ on hydrogen atoms of water
