1.6 The periodic table Flashcards
Define periodicity
the trend in properties from left to right is repeated across each period, predictions can be made about properties
Why is magnesium in the s block?
b/c:
- 1s2 2s2 2p6 3s2 - the last subshell of the electronic configuration is its assigned block, the highest energy orbital occupied by electrons
What properties of elements change as you move across a period?
- trends in electronegativity
- atomic no. increases
- metals -> non-metals
- nature of bonding changes
- increase in number of protons and electrons
Define IE
The energy require to remove one mole of electrons from one mole of gaseous atoms to form one mole of ions with a single positive charge
Why does IE decrease down a group?
shielding of outer electrons from inner electrons increases so ENC decreases
Why does IE increase across a period?
bc ANC is increasing so greater attraction for electrons
- also little variation in atomic radius and electrons are being removed from the same shell so some degree of shielding
Why is there a decrease in ionisation energy between grp 2 and 3?
bc grp 3 elements outer electron is in a new subshell of slightly higher energy level and partly shielded by s electrons so is easier to loose
Why is there a general increase in a successive IE graph?
as removing electrons from positive ion
What do the big jumps in a successive IE show?
change in shell
What does the m.p depend on?
the strength of the forces holding the particles together in a solid
why doe metallic structures have a high m.p?
bc strong electrostatic attraction between ‘sea’ of delocalised electrons
In a m.p graph, what is the type of bonding in the first three elements in a period? What does this mean for melting points?
- metallic
- increasing bc metallic bonding gets stronger, metal ions have a greatercharge and theres an increased no. of delocalised electrons
In a m.p graph, what is the type of element with the highest m.p.
What does this mean for its melting point?
- giant covalent
- each atom is covalently bonded to 4 other atoms (like diamond), high energy needed to break these bonds
In a m.p graph, what is the type of bonding present in the next three elements in a period as the m.p decreases?
What does this mean for their m.p?
- simple covalent
- decreasing as intermolecular forces are weak and easy to break + shielding is increasing so outer electrons are easier to remove
In a m.p graph, what is the type of bonding presents in the last element
What does this mean for its m.p?
- atomic
- lowest m.p and b.p bc exists as a separate atom held together by very weak temporary dipole forces
Why is there a decrease in IE between group 5 and 6?
- the electron is removed from an orbital containing a pair of electrons, the repulsion between these electrons makes the electrons easier to remove.
Define electronegativity
the ability of an element to attract a pair of covalently bonded electrons
Why does electronegativity increase across a period?
As you move from left to right across the periodic table, atoms have a greater nuclear charge and a smaller covalent radius. This allows the nucleus to attract the bonding electrons more strongly.
Why does electronegativity decrease down a group?
atomic size increases as additional electron shells are added, resulting in a larger distance between the nucleus and outer electrons.
What do we see in a reaction between each of the group 1 metal elements and water? Why?
Li+ - floats on water, gently effervesces, doesn’t melt
Na+ - melts into a ball, dashes around surface
K+ -> melts into a ball, bursts into a lilac flame
bc atomic radius increases
the outer electron gets further from the nucleus
the attraction between the nucleus and outer electron gets weaker – so the electron is more easily lost.
What is the general equation for group 1 metals and water, using M for metals?
2M + 2H20 -> 2MOH + H2
What do we see in a reaction between the group 1 metals and oxygen? Why?
Li+ - shiny when cut, slowly goes dull
Na+ - shiny when cut, quickly goes dull
K+ - shiny when cut, rapidly goes dull
Bc atomic radius increases so outer electron gets further from nucleus, reducing the attraction between the nucleus and outer electron so the electron is more easily lost
What is the general equation for group 1 metals and oxygen, using M for metals?
4M + O2 -> 2M2O
What are the flame tests for the group 1 metals?
Li+ - red
Na+ - yellow-orange
K+ - lilac
What is the reaction between group 2 metals and water?
Mg2+ - no reaction w/cold water, reacts w steam, bright light formed
Ca2+ - lots of effervescing, steady stream of bubbles, liquid goes cloudy as a white ppt of Ca(OH)2 forms
Ba2+ - greater effervescence and solution is clearer since more soluble
What is the general equation between a group 2 metal and water? (using M as a substitute for the metal)
M + 2H2O -> M(OH)2 + H2
What are all s-block metal oxides and what do they neutralise to form what? Give an example
- are strong bases and neutralise acids to form a salt and water
- MgO + 2HCl -> MgCl2 + H2O
Since hydroxides are soluble, what are they?
alkalis
What do group 1 oxides and barium oxide react with to form a soluble hydroxide? Give an example.
- water
- Na2O + H2O -> 2NaOH
Why are saturated solutions of group 2 hydroxides (exception of Ba) very weakly basic?
the conc of hydroxide is very low
Why can’t all group 2 oxides be used for the same purposes?
different basic strength
What is the flame test for the group 2 metals?
Mg2+ - no colour
Ca2+ - brick red
Ba2+ - apple green
What are all nitrates?
soluble
What are all carbonates?
insoluble
Do hydroxides become more soluble or insoluble down a group? therefore…
more soluble
Mg(OH)2 is insoluble
Ba(OH)2 is soluble
Do solutes become more soluble or insoluble down a group? therefore…
insoluble
MgSO4 is soluble
BaSO4 is insoluble
What is the general ionic equation between a group 2 metal and a hydroxide?
M2+(aq) + 2OH-(aq) -> M(OH)2(s)
What is the general ionic equation between a group 2 metal and sulphuric acid?
M2+(aq) + SO4^2-(l) -> MSO4(s)
What is the general ionic equation between a group 2 metal and a carbonate?
M2+(aq) + CO3^2-(aq) -> MCO3(s)
Why does thermal stability increase down the group 2 carbonates and hydroxides?
it becomes more difficult to break down/decompose
What is the general equation between group 2 hydroxides decomposing on heating to the oxide and steam? Do all group 2 hydroxides do this?
M(OH)2(s) -> MO(s) + H2O (g)
- yes
What is the general equation between group 2 carbonates decomposing on heating to the oxide and carbon dioxide? Do all group 2 carbonates do this?
What colour and states are all these carbonates? And the oxides? How do we test this?
MCO3 (s) -> MO(s) + CO2
- yes
- all of these carbonates are white solids
- all oxides produced are also white solids
- can test this in a lab by heating and seeing how long it takes for products/ppt to form
What are the salts halogens form called?
halides
What do halogens exist as?
diatomic molecules containing a single covalent bond
What is the colour of Cl, Br and I at room temp and what are their states?
Cl- green gas
Br- red/brown liquid
I- grey solid
What happens down the halogen group (m.p)? Why?
- mp increases as elements atomic number increases so more temporary dipoles
What are the halogens reactions with iron wool? And with sodium?
Fluorine w/iron wool= cold iron wool bursts into flames
- w/sodium = reacts violently at room temp
Chlorine w/iron wool= hot iron wool glows brightly
- w/sodium = reacts vigorously with hot Na
Bromine w/iron wool = hot iron wool glows (not as brightly)
- w/sodium = reacts less vigorously with hot Na
Iodine w/iron wool = hot iron wool shows faint red glow
- w/sodium = reacts slowly with hot Na
Why does reactivity decrease down group?
bc more shells so increase in shielding so harder to gain electron so oxidising power decreases
What is the general equation for a halogen and iron wool? (with H representative of halogen)
2Fe + 3H2 -> 2FeH3
What is the general equation for a halogen and sodium? (with H representative of halogen)
2Na + H2 -> 2NaH
What is the general electronic configuration of halogens? which block is this?
ns2 np5
block p as last subshell is p
Define a displacement reaction.
a more reactive element displaces a less reactive element from a solution of its salt
What is the ionic displacement reaction between sodium bromide and chlorine? What is reduced and what is oxidised?
2Br + Cl2 -> 2Cl +Br2
-1 0 -1 0
Chlorine is reduced
Bromine is oxidised
Fluorine can displace all other halogens from their compounds, explain that in terms of electronegativity and atomic structure.
most electronegative element so pulls electrons towards itself, smaller radius so greater ENC
