Science

3 Sub-Atomic Particles:

• Electron:

  • Charge: Negative (-ve)

  • Weight: 1/1836

  • Location: Shells

• Proton:

  • Charge: Positive (+ve)

  • Weight: 1

  • Location: Nucleus

• Neutron:

  • Charge: Neutral

  • Weight: 1

  • Location: Nucleus

Key Concepts:

• Nucleon Number: Proton + Neutrons

• Isotope: Atoms with the same element but different number of neutrons

• Ion: Atom with positive/negative charge due to valence electron transfer (Ionic bond)

  • Metals: Donate electrons (Positive charge)

  • Non-metals: Accept electrons (Negative charge)

Tests for Gases:

• Hydrogen: Burning splint

• Oxygen: Glowing splint

• Carbon Dioxide: Lime water

Reaction Types:

• Endothermic: Absorbs more energy than it releases (e.g., melting ice, photosynthesis)

• Exothermic: Releases more energy than it absorbs (e.g., freezing water, combustion)

Groups of Elements:

• Group 1 (Alkali Metals): MP/BP decrease, density increases, reactivity increases, silvery

• Group 2 (Alkaline Earth Metals): Similar trends to Group 1

• Group 7 (Halogens): MP/BP increase, reactivity decreases, colourful

  • Displacement: More reactive halogen displaces less reactive halogen

• Group 8 (Noble Gases): Inert, colourless, MP/BP increases. CAN EITHER HAVE 0 OR 8 OUTER SHELL ELECTRONS.

• Transition Metals: High MP/BP, variable reactivity, high density

Reactivity Trends:

• In metals: Increases down a group (less nucleus pull on valence electrons)

• In non-metals: Decreases down a group (greater nucleus pull on valence electrons)