Transcript 2.1 The Nature of Matter - Sonoma Valley High School

2.1 The Nature of Matter
Atoms
• Made of protons,
neutrons and
electrons.
• Nucleus holds the
protons(+) and
neutrons (0) + mass.
• Electrons (-) surround
the nucleus, in
constant motion.
Gold atoms: photograph
Elements and Isotopes
24+ elements are found in living things (of 100+
elements)
Some elements have isotopes, with different #s of
neutrons and different mass.
All isotopes of an element have the same chemical
properties b/c their electrons are the same.
Radioactive isotopes
PET scan
• The nuclei decay, releasing radiation at a
constant rate
• Used to:
– Date rocks, fossils
– Kill bacteria
Treat cancer
Act as tracers in organisms
Compounds
NaCl
H2O
• A substance formed by joining atoms together.
• The smallest unit of a compound is a molecule.
• Formulas: tell types of elements in the
compound and their ratios.
Chemical bonds
• Hold atoms together,
forming molecules
• Ionic bonds: electrons
transfer from one
atom to another,
creating a charged
particle, or ion
• Covalent bonds:
atoms share electrons
• Water is a covalently
bonded molecule
found in all living
things
Water molecules are
Attracted to one another
Van der Waals forces
• Forces of attraction between molecules.
• Hold large molecules together.
• Allow geckos to balance the pull of gravity.
These
synthetic
Carbon
nanotubes
make a ‘glue’
10X stickier
than a gecko’s
foot