2. The Periodic Table

Question 1

Name of Groups 1, 2, 17, 18

Answer 1

Group 1 - The Alkali Metals
Group 2 - The Alkaline Earth Metals
Group 17 - The Halogens
Group 18 - The Noble Gases

Question 2

Characteristics of elements in the same group & changes in elements going down a group

Answer 2

Characteristics of elements in the same group (1-2, 13-18):

1. Same number of valence electrons
2. Similar chemical properties:
   - form ions of the same charges
   - form compounds with similar chemical formulae
   - form same number of bonds when sharing electrons

Changes in elements going down a group:

1. Number of protons in an atom increases
2. Atomic radii of the elements increases because the number of electron shells increases

Question 3

Characteristics of elements in the same period & changes in elements going across a period

Answer 3

Characteristics of elements in the same period:

1. Same number of electron shells (which is equal to the period number)

Changes in elements going across a period:

1. Number of protons in an atom increases
2. Metallic character decreases/non-metallic character increases
3. Properties of oxides change from basic (metal oxides) => metalloids (amphoteric) => acidic (non-metal oxides)

Question 4

Metallic Character & Non-metallic Character

Definition

Answer 4

Metallic character:
- Defined by the ability of the atoms to lose valence electrons and form positive ions

Non-metallic character:
- Defined by the ability of the atoms to gain valence electrons by sharing electrons or forming negative ions

Question 5

Trends down Group 1

State & Explain

Answer 5

Trends down Group 1 (The Alkali Metals):

1. Melting point decreases (physical property)
2. Reactivity increases (chemical property)

• Down the group, the radius of the metal atom increases due to more electron shells. The valence shell will be further from the nucleus.
• There will be weaker electrostatic forces of attraction between the positive nucleus and valence electrons.
• Smaller amount of energy is needed to remove the valence electrons from the atom. Hence valence electrons are lost more readily (metal atoms lose electrons more readily to form positive ions).

Question 6

5 Physical Properties of Group 1 elements

Answer 6

Physical properties of Group 1 elements:

1. Good conductor of electricity (giant metallic structure)
2. Soft and can be easily cut with knife
3. Shiny, silvery solids when freshly cut
4. Low density (Li, Na, K are less dense than water)
5. Low melting points (melting point decreases down the group)

Question 7

9 Chemical Properties of Group 1 elements

Answer 7

Chemical properties of Group 1 elements:

1. Group 1 metal atoms lose their 1 valence electron readily (undergo oxidation) to form ions with 1+ charge.
2. Group 1 elements behave as powerful reducing agents as they oxidise easily.
3. Group 1 elements are highly reactive (the reactivity of Group 1 elements increases down the group).
4. Group 1 metals react vigorously with oxygen to produce metal oxides.
5. Group 1 metals react vigorously with water to produce alkaline solutions and hydrogen gas.
6. Group 1 metals react vigorously and burn brightly when heated with chlorine gas to produce white solid of metal chlorides.
7. Oxides of Group 1 metals are basic in nature.
8. Carbonates of Group 1 metals are soluble in water.
9. Carbonates of Group 1 metals are generally thermally stable (do not decompose upon heating)

Question 8

Trends down Group 17

State & Explain

Answer 8

Trends down Group 17 (The Halogens):

1. Melting and boiling points increases (physical property)

• Physical state of elements at r.t.p changes from gas to liquid to solid
• The sizes of the halogen molecules increase down the group. There are greater surface areas of interaction between the larger molecules.
• Larger amount energy is required to overcome the stronger intermolecular forces of attraction between molecules.

2. The colour of the element becomes progressively darker (physical property)
3. Reactivity decreases (chemical property)

• Down the group, the radius of the halogen atom increases due to more electron shells. The valence shell will be further from the nucleus.
• It is more difficult for the positive nucleus to attract an electron into the valence shell as the electrostatic forces of attraction are weaker.
• Electrons are gained less readily into the valence shell (halogen atoms gain electrons less readily to form negative ions).

Question 9

4 Physical Properties of Group 17 elements

Answer 9

Physical properties of Group 17 elements:

1. Low melting and boiling point (melting and boiling point increases down the group) (simple molecular structure)
2. Coloured (the colour becomes progressively darker down the group)

• F₂(g): pale yellow
• Cl₂(g): greenish-yellow
• Cl₂(aq): pale yellow
• Br₂(g): reddish-brown
• Br₂(aq): orange
• Br₂(l): reddish brown
• I₂(g): purple
• I₂(aq): brown
• I₂(s): black
• I₂ dissolved in organic solvent: purple

3. Non-conductor of electricity (simple molecular structure)
4. Generally soluble in water

Question 10

5 Chemical Properties of Group 17 elements

Answer 10

Chemical properties of Group 17 elements:

1. Group 17 halogen atoms gain 1 electron readily (undergo reduction) to form ions with 1- charge.
2. Group 17 elements behave as powerful oxidising agents as they reduce easily.
3. Group 17 elements are highly reactive non-metals (the reactivity of Group 17 elements decreases down the group).
4. Group 17 elements undergo displacement reactions.

• A more reactive halogen gains electrons more readily than a less reactive halogen.
• The more reactive halogen displaces the less reactive halogen from its aqueous halide solution

5. Group 17 elements can form both ionic and covalent compounds.

Question 11

3 Properties of Group 18 Elements

Answer 11

Physical properties of Group 18 elements:

1. Low melting and boiling points (simple molecular structure)

• All colourless gases at r.t.p.

2. Insoluble in water

Chemical properties of Group 18 elements:

1. Chemically unreactive

• Their valence shells are filled to the maximum number of electrons.
• The atoms do not gain, lose or share electrons with other atoms.

Question 12

Properties of Transition Metals

Answer 12

Physical properties of transition metals:

1. Good conductor of electricity (giant metallic structure)
2. High melting and boiling points (giant metallic structure)
3. High density
4. Most transition metals are silvery or grey in colour (except copper (reddish-brown/pink) and gold (yellow))
5. Form coloured compounds

Chemical properties of transition metals:

1. Exhibit variable oxidation states in their various compounds
2. Transition metals and their compounds are good catalysts