Periodic Table (U2) Flashcards
What are the abnormal properties of Group 1 metals?
- Very soft (cut by knife)
- Soluble in water
- Low density (float on water)
- Very low melting & boiling points
- Shiny only when freshly cut
- Highly reactive (stored under oil/kerosene)
What are the normal properties of Group 1 metals?
- Conduct electricity & heat
- Malleable & ductile
How do Group 1 metals react with oxygen?
Produce a metal oxide:
4Na + O₂ → 2Na₂O
How do Group 1 metals react with water?
Metal + water → metal hydroxide + hydrogen
Example:
* 2Na + 2H₂O → 2NaOH + H₂ (Strong alkali)
What are the observations of different Group 1 metals reacting with water?
- Lithium: Floats, fizzes, disappears steadily
- Sodium: Floats, fizzes, disappears quickly
- Potassium: Floats, fizzes, disappears very quickly, lilac flame
- Caesium: Vigorous explosion
Why do Group 1 metals become more reactive down the group?
More electron shells → outer electron farther from nucleus → weaker attraction → lost more easily
What is a use of Group 1 metals?
Titanium extraction: TiCl₃ + 3Na → 3NaCl + Ti
How is oxygen prepared in the lab?
Catalytic decomposition of hydrogen peroxide:
2H₂O₂ → 2H₂O + O₂ (Manganese oxide catalyst)
How do you prove manganese oxide is a catalyst?
- Weigh MnO₂ before reaction
- Add MnO₂ to reaction
- Filter, wash, and dry MnO₂ after reaction
- Reweigh MnO₂ → same mass as before
How do metals and non-metals react with oxygen?
- Metal + oxygen → metal oxide (basic)
- Non-metal + oxygen → non-metal oxide (acidic)
What are special combustion reactions?
- Magnesium (Mg): Bright white flame, white powder
- Hydrogen (H₂): ‘Pop’ sound, 2H₂ + O₂ → 2H₂O
- Sulfur (S): Produces toxic sulfur dioxide gas (SO₂)
How is the percentage of oxygen in air determined?
- Heat excess metal/phosphorus in air-tight apparatus
- Measure initial & final air volume
- Use formula: (Initial - Final) / Initial × 100
How is oxygen percentage found using rusting?
- Place Fe³⁺ and water in air-tight flask connected to gas syringe
- Measure air volume after 2 weeks
- Use the same formula
What are the colors of halogens in different states?
- Fluorine (F₂): Pale yellow gas
- Chlorine (Cl₂): Green gas
- Bromine (Br₂): Brown (pure), Orange (aqueous)
- Iodine (I₂): Purple (gas), Dark grey (solid), Brown (aqueous)
- Astatine (At₂): Black solid
How does chlorine react with water?
Cl₂ + H₂O → HCl + HOCl
(hydrochloric acid + hypochlorous acid)
What is chlorine used for?
Making bleaching agents (HOCl)
What is a displacement reaction example? (Group 7)
- Cl₂ + 2NaI → 2NaCl + I₂ (Brown solution forms)
Why does Br₂ displace I₂ but not Cl₂?
* Cl₂ is more reactive than Br₂, but I₂ is less reactive than Br₂
Why is CO₂ prepared in the lab?
Not abndant in nature, It is only 0.03% of atmospheric air
How is CO₂ prepared?
Thermal decomposition of metal carbonate:
* Example: CuCO₃ → (Heat) CuO + CO₂ (Green to black solid)
Acid + metal carbonate reaction:
* Metal carbonate + acid → Salt + H₂O + CO₂
Why should you avoid reacting calcium carbonate with sulfuric acid?
CaSO₄ forms an insoluble layer → stops reaction
What are the uses of CO₂?
- Fire extinguishers: CO₂ is denser than air & non-flammable
- Fizzy drinks: CO₂ dissolves in water under pressure
