Group 0: Noble Gases:
- All noble gases are colourless, inert, and monoatomic.
- Monoatomic: Consisting of single atoms
- Inert: Unreactive
Noble Gases:
Helium → He
Neon → Ne
Argon → Ar
Krypton → Kr
Xenon → Xe
Radon → Rn
Electronic Configuration:
In chemical reactions, only electrons are involved.
- The noble gases all have full outer shells, which makes them inert. They're unable to form ions as they have full outer shells, which makes them already stable.
- Boiling points increase as you go down Group 0 as the intermolecular forces weaken. More energy is required to overcome these forces.
- The density increases going down to group 0. Density refers to the amount of substance contained within a specific volume.
- Noble gases are non-flammable as they're inert and cannot react with oxygen.
Questions:
When answering questions, use the format DESE.
Distance between a nucleus and an outer electron.
Electrostatic attraction between nuclei and outer electrons.
Shielding—how many shells there are.
Ease of losing/gaining an electron.
Alkali Metals
→ Group 1 atoms get larger as you go down group 1.
- Group I atoms need to lose 1 electron to gain a full outer shell.
- Ion charge = +1
Reactivity answers using DESE:
- The distance increases between the nucleus and the outer electron, and so there is a decrease in electrostatic attraction between the outer electron and nucleus.
- Therefore, the shield increases, and less energy is required to remove an electron from the outer shell.
- This means down group 1 reactivity increases, and the element can react easily.
- The electrostatic force of attraction is what holds the electron in place. The electron is held in place by the positively charged nucleus and negatively charged electrons.
- The reactivity increases down the group as the distance between the nucleus and outer electron increases. Therefore, the outer electron is easier to lose down the group.
- As you go down the group, the reactions with water become more vigorous.
When a Group 1 metal reacts with water, it forms metal hydroxide and hydrogen gas.
- Eg., Lithium + Water → Lithium Hydroxide + Hydrogen
- Li(s) - 2H2O(l) → 2LiOH(aq) + H2(g)
- Li, Na, and K are very easy to cut, are dull grey on the outside, shiny when cut, float on water, and are solids at room temperature. Potassium ignites easily when it reacts with water. Hydrogen test = use a lighted splint and pops if H2 is present.
- When group 1 metals react with water, they form alkaline solutions (universal indicator: purple).
- The melting points decrease as one moves down Group 1.
- Observations:
- Li → Steady effervescence, floats, moves on the surface of the water, disappears.
- Na → Rapid effervescence, floats, moves on the surface of the water, melts into a ball/round, disappears.
- K → Vigorous effervescence, floats, moves on the surface of the water, melts into a ball/round, and disappears.
* General Diagram - Reactions of Group 1
The Halogens
Fluorine (F2): Pale yellow gas
Melting point: -220°C
boiling point: -188°C
Electronic arrangement: 2,7
Chlorine (Cl2): Pale green gas
Melting point: -102°C
Boiling point: -34°C
Electronic arrangement: 2,8,7
Bromine (Br2): Brown liquid
Melting point: -7°C
Boiling point: 59°C The vapour is orange.
Electronic arrangement: 2,8,8,7
Iodine (I2): Grey solid
Melting point: 114°C
Boiling point: 184°C Vapour is purple.
Electronic arrangement: Ends in 7
Astatine (At2): Black solid
Melting point: 302°C
Boiling point: 337°C
Electronic arrangement: Ends in 7.
- The boiling/melting points become higher, and atoms become bigger. The colours turn darker.
- All halogens are atoms containing diatomic molecules that are particle elements. Two atoms form a chemical bond.
- As you go down to Group 7, the reactivity decreases. This increases the electrostatic force between the nucleus and electrons on the outer shell.
- The shielding increases too. This implies that obtaining the outer electron becomes more challenging, requiring more energy due to the presence of more shells.
- Safety: Cl2(g) is a toxic gas, so it's only used in a fume cupboard. Br₂ is a toxic liquid, so gloves should be worn.
+ Halogens gain an electron when they react.
Halogen Displacement
- A halogen displacement reaction is where a more reactive halogen takes the place of a less reactive halogen in a compound.
Halogen: Chlorine
Colour of solution: Pale green
Group 1 halide: Sodium Chloride
Colour of solution: Colourless
Halogen: Bromine
Colour of solution: Orange
Group 1 halide: Sodium Bromide
Colour of solution: Colourless
Halogen: Iodine
Colour of solution: Brown
Group 1 halide: Sodium Iodide
Colour of solution: Colourless
When dissolved in water:
Cl2(aq) → Colourless solution
Br2(aq) → Orange solution
I2(aq) → Brown solution
- The names of the elements in Group 7 end in '-ine', but their ions end in '-ide' (e.g., iodine → iodide).
Group 1 halides are all white ionic solids and form colourless solutions.
E.g., Chlorine + Sodium Bromide → Sodium Chloride + Bromine
Cl2(aq) + 2NaBr(aq) → 2NaCl (aq) + Br2(aq)
1. Bromine + Potassium Iodide → Potassium Bromide + Iodine
The colourless solution will turn → brown as iodine forms.
2. Iodine + Potassium Chloride → No reaction
Chlorine is more reactive than iodine so there's no observable change.