C6 Flashcards
What groups are 1,7 and 0 called?
1-alkali metals.
7-halogens.
0-noble gases.
Because all elements in same groups share similar properties so are all in the same group on the table.
Alkali metal properties
Soft-can be cut with a knife.
Have relatively low melting points.
Low densities(first three can float in water).
Reactions of lithium, sodium and potassium with water
Lithium-fizzes steadily, slowly becomes smaller until disappears.
Sodium-melts to form a ball, fizzes rapidly, quickly becomes smaller until disappears.
Potassium-quickly melts to form a ball, burns violently with sparks and a lilac flame, disappears rapidly often with a small explosion.
Pattern of reactivity of alkali metals
React with water to produce a metal hydroxide and hydrogen(alkali is a base that dissolves in water to form an alkaline solution).
Reactivity of these metals increase going down the group.
Explanation of this pattern of reactivity
To take part in a reaction, these metals atoms lose their outer electron to form positively charged ions(cations).More easily these form the more reactive it is.
Reactivity increases as you go down the group because:
-Atoms become larger.
-Outer electron become further away from the nucleus.
-force of attraction between nucleus and outer electron decreases.
-meaning the electron is lost more easily as the amount of shells increase as you go down the periods.
Colours and physical states of chlorine, bromine and iodine at room temp
Chlorine-Pale green gas.
Bromine-brown liquid.
iodine-purple/black solid.
Physical properties patterns of halogens
Going down group 7, boiling points and melting points increase because:
-the molecules become larger.
-the inter-molecular forces become stronger.
-more energy is needed to overcome these forces.
Chemical test for chlorine
-Damp litmus paper
-is bleached white when it is laced in chlorine.
-if damp blue litmus paper used, paper turns red then white.
Reactions of halogens with metals
Forms a metal halide.
Chlorine-hot iron wool burns vigorously to produce orange brown iron(3) chloride.
Bromine-burns quickly to produce red brown iron(3) bromide.
Iodine-reacts slowly in iodine vapour to produce grey iron(2) iodide.
Halogen reactions with hydrogen
Produce compounds called hydrogen halides.
Gases at room temp.
Dissolve in water to produce acidic solutions.
CL-explodes with a flame or in sunlight forming hydrogen chloride.
Br-Vigorous reaction with burning H2=hydrogen bromide.
Iodine-Very slow reaction when heated strongly forming some hydrogen iodide.
relative reactivity of halogens
Become less reactive going down group 7 because of opposite reason to alkali metals:
-need to gain 1 electron to react to form negative ions.
-atoms become larger.
-outer shell becomes further away from nucleus.
-force of attraction between nucleus and outer shell decreases.
-outer electron is gained less easily.
-halogens become less reactive as you go down group 7.
Halogen displacement reactions
A more reactive halogen can displace a less reactive halogen from solutions of its salts.
Cl+potassium iodide>potassium chloride+iodine because chlorine is more reactive than iodine.
Why halogen displacement reactions are redox reactions(gain and loss of electrons) and which are oxidised and which are reduced.
-Reduction and oxidation happen at the same time so are redox reactions.
Atoms Gain electrons=reduced.
Loses electrons to form molecules=oxidised.
Why are noble gases chemically inert
Already have a full outer shell so have no tendency to gain or lose electrons or share electrons so are inert and do not take part in chemical reactions.
Properties of noble gases
Low boiling point-boiling point increases going down the group because more shells and stronger forces so more energy needed.
low densities-density increases going down the group because more particles per volume.
Inert-so not flammable.
