C7.1 The Periodic Table
Download
Report
Transcript C7.1 The Periodic Table
G8 Science
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
2 of the 92 are liquids: Br, and Hg
Elements are solid when intermolecular forces
are stronger than thermal motion.
Noble gases (group 18) are gases because
their valence shell is full, with 8 electrons,
and so they have a weak intermolecular force
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.
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.
Good electrical conductors allow electrons to
flow easily through them. This is a property of
metals.
Most metals are good thermal conductors
Elements to the right of the table are good
insulators, i.e. poor conductors.
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
< .01% of Earth’s crust
Most molecules that make up plants and
animals are build around carbon (Organic
Chemistry)
Pure carbon
◦ Diamond
Tetrahedral crystal,
Hardest natural substance (diamond tip drill bits)
Highest thermal conductivity
◦ Graphite
Sheet like
Lubricant for locks and keys
Silicon
◦ Second most
abundant element in
Earth’s crust (after
Oxygen)
◦ Sand, rocks, minerals
◦ Glass (SiO2)
◦ Semiconductors (also
make with
Germanium)
Nitrogen
◦
◦
◦
◦
◦
Colorless, tasteless, odorless
78% of Earth’s atmosphere
N2
Boils at -196°C
Crucial to to life
Oxygen
◦ 21% of Earth’s atmosphere
◦ 46% of Earth’s crust
◦ Crucial to life
Phosphorus
◦ Key ingredient in
DNA
◦ Glow in the dark