SC17 Flashcards
(16 cards)
What is the electronic configuration of alkali metals and what does this mean?
All have one electron in their outer shell:
1. They are all found in group 1 of the periodic table
2. They have similar physical properties
3. They can readily lose the outer shell electron to form positive ions with a +1 charge and a full outer shell.
What are the properties of alkali metals?
- Soft (can be cut by knife) - softness increases down the group
- Low density
- Low melting and boiling points - decrease down the group
- Good conductors of heat and electricity
- Shiny (only seen when freshly cut, then quickly tarnish due to reaction with oxygen)
How does electronic configuration affect reactivity of alkali metals?
Outer shell electrons get further away from nucleus because there are more filled shells between nucleus and outer shells. More shells creates more shielding which means force of attraction between positive nucleus and negative outer electron gets weaker. The outer electron is therefore more easily lost during chemical reactions, increasing reactivity as we go down the group.
- Outer shell electrons further from nucleus
- Easier to lose electrons
- Weaker forces of attraction –> increased reactivity down group
What happens when alkali metals react with water?
They form alkaline hydroxides - reaction gets faster and more vigorous down the group.
What are the different reactions of alkali metals with water?
Check teacher notes SC17 slide 11 table.
Why are alkali metals corrosive?
They react with water on the skin to form a corrosive alkaline solution.
What are the properties of halogens?
- Boiling point increases down the group
- Very reactive non-metals
- Toxic and corrosive
- Some can be used as disinfectant (e.g. chlorine)
What is the electronic configuration of halogens and what does this mean?
All have seven electron in their outer shell:
1. Can easily obtain full outer shell by gaining one electron
2. Form negative ions (-1 charge)
3. Have similar chemical properties
How does electronic configuration affect reactivity of halogens?
Reactivity of halogens decreases going down the group. This is because outer shell electrons are further away from the nucleus causing the forces of attraction between nucleus and outer shell electrons to become weaker. This makes it more difficult to gain an electron to complete the outer shell during chemical reactions.
- Reactivity decreases going down group
- Outer shell further from nucleus –> weaker forces of attraction
- More difficult to gain electrons
What happens when halogens react with metals?
They gain an electron to complete their outer shell forming an ionic compound, also called metal halides.
What happens when halogens react with hydrogen?
They form hydrogen halides - gases at room temperature which can dissolve in water to form acidic solutions.
What is the test for chlorine gas?
Damp blue litmus paper reacts with chlorine gas and becomes red then bleaches white.
How does displacement occur in halogens?
A more reactive halogen will always displace a less reactive halogen from its compounds in solution.
What are the characteristics of noble gases?
Very unreactive thus described as inert gases.
How does electronic configuration affect reactivity of noble gases?
Noble gases have full outer shell electrons. This means that they are very stable and the most unreactive/inert of all elements since they do not need to gain, lose or share electrons. All noble gases are similarly unreactive so they do not normally form bonds with other elements and are monatomic.
- Full outer shell
- Very stable, unreactive/inert
- Monatomic
- Similar to each other
What are properties of noble gases?
- Density increases down the group
- Boiling point increases down the group
