periodic table

Question 1

Common properties of alkali metals

Answer 1

1. They are all reactive metals. They have to be stored under oil to stop them reacting with oxygen and water vapour in the air
2. They are soft and can be cut with a knife.
3. They all have low melting points and low densities compared to other metals,
4. They form positive ions with +1 charge.

Question 2

Reaction with water

Answer 2

They react spontaneously with water to produce hydrogen gas and the metal hydroxide (alkali). The reaction is exothermic.
Metal + water → metal hydroxide + hydrogen

2Li + 2H2O → 2LiOH + H2
2Na + 2H2O → 2NaOH + H2

Question 3

alkali metals Reaction with non-metals

Answer 3

They react strongly and directly with non-metals to form salts. These salts are white, crystalline and ionic solids which dissolve in water.

Question 4

General trends down the group 1

Answer 4

(a) decreasing melting point
(b) increasing density
(c) increasing reactivity

Question 5

Explain why the reactivity of group 1 metals increases as you go down the group.

Answer 5

The atomic radius increases down the group (the atoms get larger).

The force of attraction between the nucleus and outer electron decreases.

The electron is lost more easily (requires less energy to remove) from atoms lower down the group.

Question 6

What are the general properties of transition metals?

Answer 6

• Relatively high densities.
• High melting points.
• Form coloured compounds.
• Often act as catalysts.

Question 7

‘Transition metals have variable
____ ____’

Answer 7

Oxidation states

Question 8

Example of oxidation states

Answer 8

Example: iron atoms can lose either two electrons, to form Fe2+ ion, or three electrons, to give Fe3+.
Iron(III) oxide ,Fe2O3
Iron(II) oxide ,FeO

Question 9

REACTION WITH WATER
Lithium
Sodium
Potassium

Answer 9

Lithium Floats and gives off hydrogen gas (effervescence)
Sodium Vigorous Reaction and moves very quickly
Potassium Explosive Reaction, lilac flame

Question 10

Hallogens properties

Answer 10

• density and melting point increase down the group
• Poisonous
• Down the group, the colour darkens
• They produce salts called halides
  Example: chlorides, bromides, iodides
• Diatomic
• Reactivity decreases down the group,
  (because it has to gain an electron,
  so the closer the electron is to the positive nucleus, the more easily it will be gained,
  so atoms with fewer shells will react more easily)
• Do not conduct electricity

Question 11

The colour and state of each element in group 7 at r.t.p
fluorine
chlorine
bromine
iodine
astatine

Answer 11

fluorine – pale yellow gas
chlorine – pale yellow-green gas
bromine – red-brown liquid
iodine – grey-black solid
astatine – black solid

Question 12

What happens in a displacement reaction

Answer 12

A halogen displacement reaction occurs when a more reactive halogen displaces a less reactive halogen from an aqueous solution of its halide

Question 13

Colour in solutions
Halide salts (e.g. KCl, KBr, KI)
Chlorine water
Bromine water
Iodine water

Answer 13

Halide salts (e.g. KCl, KBr, KI) are colourless
Chlorine water is colourless
Bromine water is orange
Iodine water is brown

Question 14

Noble gas properties

Answer 14

non-metals
have very low melting and boiling points
all monoatomic
colourless gases
Density. m.p & b.p increases down the group

Question 15

Why are noble gases inert?
(‘inert’ means chemically unreactive)

Answer 15

The atoms have a full outer shell of electrons

Question 16

Uses of-
Helium
Argon
Neon

Answer 16

Helium-filling balloons (is less dense than air and does not burn)
Argon – Lamps
Neon – advertising signs