periodic table Flashcards
Why does COCl2 have a trigonal planar shape?
C has 3 electron dense
regions
electron pairs/bonded
pairs/bonded regions repel
At room temperature and pressure, the first four members of the alkanes are all gases but the
first four alcohols are all liquids.
Explain this difference in terms of intermolecular forces.
Alcohols have hydrogen bonds
(and induced dipole dipole forces)
Hydrogen bonds are stronger than
induced dipole dipole forces (in alkanes)
Describe what a dative covalent bond is.
a covalent bond (a shared pair of electrons) in which both electrons come from the same atom
The reactivity of the Group 2 elements Mg–Ba increases down the group.
Explain why
Increasing size:
Atomic radius increases OR more shells OR
more (electron) shielding
Attraction:
Nuclear attraction decreases OR
(outer) electron(s) experience less attraction
Ionisation energy:
Ionisation energy decreases OR
less energy needed to remove electron(s)
Describe the difference between induced dipole-dipole forces, permanent dipole-dipole forces, and hydrogen bonds.
induced dipole dipole forces: temporary polarity caused by the movement of electrons in molecules
permanent dipole dipole forces: weak intermolecular forces of attraction that arise between permanently polar molecules
hydrogen bonds: when a hydrogen atom bonded to a strongly electronegative atom exists in the vicinity of another electronegative atom with a lone pair of electrons. Only act between hydrogen and nitrogen, oxygen, or fluorine.
First ionisation energies decrease down groups in the Periodic Table.
Explain this trend and the effect on the reactivity of groups containing metals
Atomic radius:
larger atomic radius OR more shells
Effect of nuclear charge/shielding:
Increased nuclear charge is outweighed by
increased distance/shielding OR
more/increased shielding
Reactivity AND Nuclear attraction:
Reactivity increases AND less nuclear attraction
OR
less attraction on electrons
Explain the differences in the melting points of sodium and magnesium, using the model of
metallic bonding.
Magnesium has more outer OR bonding electrons
Magnesium ions have a greater (positive) charge
(density)
Magnesium has a greater attraction between ions
and delocalised electrons
Describe the order in which tests for ions should take place.
1) carbonate test: neither sulfate nor halide ions produce bubbles with dilute acid
2) sulfate test: barium carbonate is also white and insoluble in water
3) halide test: silver carbonate and silver sulfate are both insoluble and form precipitates.
Describe the test for halide ions
add aqueous silver nitrate to solution of aqueous halide, will form precipitate
AgCl- white AgBr-cream AgI-yellow
Add aqueous ammonia to differentiate between the colours: AgCl soluble in dilute NH3, AgBr soluble in conc. NH3, AgI insoluble in NH3.
Describe test for carbonates
1) add dilute nitric acid to solid/sol.
2) if effervescence produced, test by bubbling in limewater. Limewater will turn cloudy if carbon dioxide bubbles.
Describe test for sulfates
Add barium nitrate, white precipitate will form
Describe test for ammonium ions
heat aqueous sodium hydroxide, ammonia gas will turn damp red litmus paper blue.
State the benefits and risks of using chlorine in water treatment
Benefit: kills bacteria
Risk: toxic/poisonous
OR forms chlorinated
hydrocarbons
OR forms carcinogens/toxic
compounds
What is disproportionation
One element is oxidised and reduced in the same reaction
