1. G8 Science

2. Room Temperature  Most pure elements are solid a room temperature  11 of the 92 naturally occurring elements are gas: H, He, N, O, F, Ne, Cl, Ar, Kr, Xe, Rn

3.  2 of the 92 are liquids: Br, and Hg  Elements are solid when intermolecular forces are stronger than thermal motion.

4.  Noble gases (group 18) are gases because their valence shell is full, with 8 electrons, and so they have a weak intermolecular force

5. Periodic Properties  First elements have a low melting and boiling point. They increase until you reach the middle of the table, then decrease again.  Melting and boiling points reflect strong intermolecular forces.

6.  Intermolecular forces are strongest when the valence shell is half full – because a half full valence shell has the most electrons to participate in bonding.

7. Thermal and Electrical Conductivity  Good electrical conductors allow electrons to flow easily through them. This is a property of metals.  Most metals are good thermal conductors

8.  Elements to the right of the table are good insulators, i.e. poor conductors.

9.  An alloy is a solid mixture of one or more elements, of which one is a metal.  Steel – iron and carbon (rusts but stronger than iron)  Stainless steel – iron, carbon, chromium, vanadium, manganese (does not rust)  Bronze – copper, tin  Brass – copper, zinc  Aluminum alloys  Titanium alloys

10.  <.01% of Earth’s crust  Most molecules that make up plants and animals are build around carbon (Organic Chemistry)

11.  Pure carbon ◦ Diamond  Tetrahedral crystal,  Hardest natural substance (diamond tip drill bits)  Highest thermal conductivity ◦ Graphite  Sheet like  Lubricant for locks and keys

12.  Silicon ◦ Second most abundant element in Earth’s crust (after Oxygen) ◦ Sand, rocks, minerals ◦ Glass (SiO 2 ) ◦ Semiconductors (also make with Germanium)

13.  Nitrogen ◦ Colorless, tasteless, odorless ◦ 78% of Earth’s atmosphere ◦ N 2 ◦ Boils at -196°C ◦ Crucial to to life  Oxygen ◦ 21% of Earth’s atmosphere ◦ 46% of Earth’s crust ◦ Crucial to life

14.  Phosphorus ◦ Key ingredient in DNA ◦ Glow in the dark