Experiment: Tube with cathode at one end and anode at the other. Voltage running
through it with a phosphor causes light to shine out of it. Known as a cathode ray (what
TVs used). A magnet was placed next to phosphor and the color was shifted due to
“negative particles” (electrons).
Experiment: Sheet of gold that was 6 nanometers thick was shot at by alpha particles.
Most went through, but some were reflected back. Hypothesis – Atoms have a core that
occupies volume that can cause incoming molecules to bounce off.
In periodic table, lower left number is the atomic number (number of protons or
electrons). The upper left is the mass number (number of protons and neutrons). Elements
on left are more reactive while those on the right are stable due to having all core
same number of protons and electrons
different number of neutrons
p = 11
e = 11
n = 13
Mole and Avogadro’s Number
Mole uses a single molecule.
Different mass for different compounds.
It is the number of atoms in 12g of C.
Mole is the standard unit for measuring the amount of _________ (atoms, particles, etc.)
that makes up a substance.
Mole always has the same number of particles regardless of the nature of the particle.
Ex. 1 mole C = 6.02 x 10
Molar mass is the mass of one mole of the element in grams.
Ex. 1.0079 g of H in one mole = 1.0079 g/mol
Ex. 8 g He
1 mol/4.003 g = 2 mol of He ▯# of atoms Organic Compounds – have carbon
Inorganic Compounds – everything else
Molecules – neutral collection of atoms that are strongly attracted and act as a single
Charged molecules are called ions.
Cations are positively charged.
Anions are negatively charged.
***bonds between charged molecules is weaker tha