Chapter 16: Periodic Table Flashcards
Define the periodic table.
The periodic table is a list of elements arranged in order of increasing proton numbers.
How do the metallic properties of elements change across a period?
From left to right across a period, there is a decrease in metallic properties and an increase in non-metallic properties.
How does the nature of oxides of elements change across a period?
Group I and II: Basic oxide (metal oxides which react with acids to form a salt and water)
Group III: Amphoteric oxide (metallic oxides which react with both acids and bases to form salts and water)
Group IV to VII: Acidic oxide (non-metal oxides which dissolve in water to form acids and react with alkalis to form a salt and water)
How do the metallic properties of elements change down a group, and why?
There is an increase in metallic properties and a decrease in non-metallic properties. Going down a group, the size of the atom increases. This means that the valence electrons of an element will be further away from the attractive force of the nucleus. An element further down a group will thus lose its valence electrons more easily.
What is the relationship between the period number that an element belongs to, and its electronic structure?
The number of electron shells is the same as the period number of the element.
State the physical properties of Group I metals (alkali metals).
1) Soft
2) Low melting points and boiling points
3) Low densities (Li, Na and K float on water as their densities < density of water)
State the chemical properties of Group I metals (alkali metals)
1) Reactive
2) Has 1 valence electron (achieve stable octet configuration. Special case: lithium achieves duplet configuration)
3) Reacts with cold water to form alkali and H2 gas
4) Powerful reducing agents
5) Form ionic compounds
State the group trends for Group I metals.
Down the group,
1) m.p. and b.p. decrease
2) density increases
3) reactivity increases.
4) reducing power increases
Why does the reactivity of group I metals increase down the group?
Down the group, atomic radii increases. Hence, the electrostatic attractions between the positively charged nuclei and the negatively charged electrons are weaker and it is hence easier to lose the valence electrons.
Why does the reducing power of group I metals increase down the group?
Reducing power increases down the group as the metals lose electrons more readily down the group. This means that down the group, they have a higher tendency to be oxidised (and hence act as better reducing agents)
Half ionic eqn: Li (s) → Li+ (aq) + e-
State the physical properties of Halogens (group VII elements) and the group trends in relation to these properties.
1) Low m.p. and b.p.
2) Coloured
Down the group,
1) m.p. and b.p. increase
2) Colour becomes darker
Why do the m.p./ b.p. of halogens increase down the group?
Down the group, the molecular masses/ sizes of halogens increase. Hence, van der waal forces of attractions between molecules increase, and a greater amount of energy is required to break it.
State the chemical properties of Halogens (group VII elements) and the group trends in relation to these properties.
1) Diatomic molecules
2) Gaseous
3) Good oxidising agents (gain electrons during chemical reactions while reducing itself)
X2 + 2e- → 2X-
4) Gain 1 electron to achieve stable octet configuration (stable noble gas structure)
5) React with metals to form salts called halides
6) Reactivity decreases down the group, so oxidising power decreases down the group
Explain how halogen displacement reactions work, and give an example of a reaction between Cl2 and KBr while stating the observations made from the reaction.
- A reaction in which one element takes the place of another element in a compound
- A more reactive halogen will displace a less reactive halogen from its halide solution
Cl2 (g) + 2KBr (aq) → 2KCl (aq) + Br2 (aq) Colourless solution (KBr and KCl are both colourless, no change) turns brown (Br2)
State the standard ionic equation for halogen displacement.
X2 (aq) + 2Y- (aq) → 2X- (aq) + Y2 (aq)
State the properties of transition metals.
1) High m.p. and b.p.
2) High densities
3) Variable oxidation states
4) Form coloured compounds
5) Commonly used as catalysts
State the properties of noble gases.
1) Monoatomic
2) Colourless gases at rtp
3) Low m.p./ b.p.
4) Insoluble in water
5) Unreactive
Also called inert gases/ rare gases
Name the colours of:
1) Cl2 (aq)
2) Br2 (aq)
3) I2 (aq)
1) Cl2 (aq): colourless
2) Br2 (aq): brown/ orangey brown
3) I2 (aq): reddish brown
