Group 7 Halogens

The properties of Group 7 elements (halogens) include:

• Non-metallic properties: brittle, dull solids, poor conductors
• Diatomic molecules with weak intermolecular forces
• Seven electrons in outermost shell
• Form covalent bonds and 1- ions (halide ions) in reactions

Trends and properties in Group 7 halogens down the periodic table:

• Colors become darker
• Reactivity and bleaching effect decrease
• Density increases
• Melting and boiling points increase

Vocabulary: Diatomic - Consisting of two atoms

Example: The diatomic halogens are F₂, Cl₂, Br₂, and I₂

Group 1 Alkali Metals

The physical properties of alkali metals in Group 1 include being soft, low density, and having relatively low melting and boiling points. They are shiny when freshly cut and good conductors of electricity and heat.

Key chemical properties of Group 1 alkali metals:

• Form alkaline solutions when reacting with water
• Have one electron in outermost shell
• Increase in reactivity down the group
• Form 1+ ions when reacting
• Number of electron shells increases down group

Example: The general equation for alkali metals reacting with water is: 2M (s) + 2H₂O (l) → 2MOH (aq) + H₂ (g)

Highlight: Alkali metals must be stored in oil to prevent reaction with oxygen and water vapor in air.

Vocabulary: Alkalinity - The property of being alkaline or basic (pH greater than 7)