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Chapter 2
Anything that has mass and volume
Elements = simplest stable form of matter
Made of atoms
Compounds = chemically combined
• Made of molecules
Remember this
98% of crust is 8 elements and their compounds
Atomic Structure
• Small electrons in cloud
(- charge)
• Much larger protons in
nucleus (+ charge)
• Slightly larger neutrons
in nucleus (0 charge)
• Every element unique
• Common units of mass, such as grams, are much
too large to conveniently describe the mass of an
atomic nucleus or any of its constituent parts. To
solve this problem a new unit was defined: the
atomic mass unit (amu). The atomic mass unit is a
relative unit defined arbitrarily by assigning a
mass of 12 amu to the neutral atom carbon-12, the
common isotope of carbon. One atomic mass unit
equals 1.66 X 10-24 grams. Employing this value,
the masses of the fundamental particles of an
atom have been determined to be:
• (1) Proton mass: 1.00727 amu.
• (2) Neutron mass: 1.00867 amu.
• (3) Electron mass: 0.00055 amu.
= atomic number
= atomic mass
• Forms of the same
• Differ in # of
• Same atomic
number but different
atomic mass
• Similar behavior
with some different
• Leads to average
atomic mass
• H = 1.00794 amu
Valence electrons create
behaviors/properties and establish
periodic groups on table
• Metals have 1-3 valence electrons and
lose them easily
• Non-metals have 4-7 electrons and tend to
gather more
Mendeleev’s Table
2 and 8 electrons create unreactive
state (Happy) Is this important?
How do they become “happy”?
Chemical bonding!
Ionic bond – giving/taking e-
Covalent bond – sharing e-
Polar covalent molecule
Van der Waal’s Forces
• Dispersion interaction
– Between any molecule with unbalanced
• Dipole-dipole attraction
– Between polar molecules like water
• Unlike a compound, the components are
not chemically combined, just physically
• Heterogenous – not equally mixed
• Homogenous – “solution” and equally
mixed (dissolved)
• Suspension – equally mixed small
components and suspended
• Colloid - equally mixed larger components
and suspended
Left: Fine sand (silica) added to water will quickly settle,
producing a heterogeneous mixture with water on top and
silica on the bottom. Right: The same proportion of silica,
specially prepared, produces something different. The
particles of hydrated silica are much larger than atoms and
ordinary molecules. The similarly charged silica particles
repel one another and stay suspended indefinitely, which is
a colloid.
• Dissolved
• Weak acid or base
• React with strong
acids and bases to
prevent sharp,
sudden changes in