Group 2 & Group 7 Flashcards
Group 1 & Group 2 have the same trends
Atomic Radius
- Down G2, INCREASES
↳ more QL = more electrons →electrons are further away : easier to remove
Ionisation Energy
- Down G2, DECREASES
↳ more QL = further away electrons →easier to remove : less energy needed
Mp/Bp
- Down G2, DECREASES
↳ atomic radius increases = outershell has lower nuclear charge (between cation & electron)
↳ less energy is needed to break this making the mp/bp lower
Reactivity to water
- Down G2, increases
↳ atomic radius increases = outer electron is further away
↳ reacts w water easily
G2 react w water produce HYDROXIDES
G2 burn in oxygen forming OXIDES
G2 react w chlorine forming CHLORIDES
Trend
Every G2 elements form ionic bonds except Berilium which forms covalently
* BeO doesn’t react w water (exception)
* MgO reacts slowly w water
Down G2, reactivity increases
- Alkaline solutions become stronger
↳ the hydroxide ions become more soluble
-hydeoxides form more quickle : the pH of the solution goes above 7
G2 Oxides react w water
G2 Oxides react w dilute acid
Solubility Trend
Hydroxide
Down G2, increases in hydroxide ions (OH)
* more soluble : pH goes above seven
↳ meaning that it will dissolve faster
Solubility Trend
Sulfate
Down G2, decreases in sulfate ions (SOv4 -2)
* become less soluble
↳ dissolve slower
Thermal Stability
Applied heat needed to break something down
Large ions are Destabilised/Polarised/Distorted by cations
Carbonates/Nitrates
They’re broken down by negative ions
Thermal Stability
Trend 1)
Greather distortion = more unstable the compound
Thermal Stability
Trend 2)
Larger cations = smaller distortion than small cations
↳lower charge density
-down G2 atomic radius increases
↳ electrons = further away & ion can’t hold onto them
↳ if it can’t even do this, then it can’t pull another’s electrons
Charge Density
Charge per space/ Charge over smaller space
Larger cation = lower CD
↳ less distortion = more stable the nitrate/carbonate compound
Top G2 = most polarising
Smaller atomic radius = more polarising
Higher charge = more polarising
G2 cations have a 2+ charge compared to a +1 from G1 so G2 carbonates/nitrates = less stable than G1
Anions
Thermal Stability Testing
Nitrate Decomposition
- Test to see how long it takes for a certain amount of O2 to be released
Glowing splint relights if positive
- Test to see how long it takes for NO2 to form
NO2 gas is brown
Anion
Thermal Stability Testing
Carbonate Decomposition
- Test to see how long it takes for a certain amount of CO2 t be released
Limewater goes cloudy if positive
Cation
Flame Test
Equipment
- HCl
- Metal solutions (cations)
- Nichrome wire
- Bunsen Burner
Cation
Flame Test
Practical done because some metals have the same colour
- Take nichrome wire & dip into HCl
- Put that wire into flame
↳ step 1 & 2 cleans loop - Dip wire into one of the metal solutions
- Place that wire into the flame at 45° just below top of the flame for 5 secs
- Observe colour & note it down
- Repeat 1-8 until you’re done w all solutions
- Repeat procedure again for each solution
↳ some reactions occur quickly : recheck colour
!!If all tests are orange, your test is contaminated!!