Describe the development of the periodic table.
Dalton (atomic weights + had symbols for each element) -> Newlands (law of octaves, broke down after carbon) -> Mendeleev -> modern (organised by proton number and no longer atomic weight)
Describe why Mendeleev’s periodic table was successful.
- left gaps for undiscovered elements
- switched some elements if their properties fitted better in another group
Why are noble gases so unreactive ?
They have a full valence shell so do not need to form ions to become structurally stable.
Explain why the reactivity of elements increases down group 1.
- g1 loses 1 outer electron to form a positive ion
- as go down the group, shielding effect of other energy levels between the nucleus and outer energy level means that the nucleus has less attraction to outer electron, so it is easier to lose
- element reacts more quickly if has more energy levels
Explain why the reactivity of elements decreases down group 7.
- g7 must gain 1 electron to be stable (negative ion)
- easier to gain electron if have strong electrostatic force of attraction between nucleus and outer energy level
- if more energy levels down the group, shielding effect, not able to gain as easily/quickly
- element is less reactive
Describe an investigation of the reactions of lithium, sodium and potassium in water. Include observations.
LITHIUM
- mildest reaction
- moves around in water (just below surface)
- fizzing
- sml amt gas given off
- metal becomes smaller then disappears
- UI turns blue in water once dissolved
SODIUM
- moves faster on surface of the water
- pearling
- more vigorous fizzing
- gas released (hydrogen)
- dark blue in UI
POTASSIUM
- ignites in lilac flame
- pearling
- moves around on surface of water
- more gas released
- melts + disappears quickly
- darker blue/purple in UI
What is a displacement reaction ?
When a more reactive halogen displaces a less reactive halogen from its solution
Why can’t be fluorine be used in reactions with aqueous solutions ?
Its reaction with hydrogen is extremely violent.
What are the physical properties of transition metals ?
- good conductors
- hard and strong
- high density
- high melting points
- makes them good for structural materials, cookware and electrical components
What are the chemical properties of the transition metals ?
- react (more) slowly (than g1 metals)
- resistant to corrosion (apart from iron which may rust and weaken structures it is used in)
What is special about the compounds of transition elements ?
They are coloured.
