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Study Guide for Chemistry Midterm 2
Matter
 Made of particles(atoms/molecules)
 Properties based on identitites/ nature of particles
o Physical state of room temp
o Melting/boiling pts
o Density
o Reactivity
o Physical appearance
o Pliability
Matter

Mixtures

Heterogeneous
Mixtures
(muddy water,
pecan pie)

Separate physically

Homogeneous
Mixtures
(solutions,
alloys)

Pure substances

Compounds

Separate

Elements

(water,
ammonia)

chemically

(Iron,
oxygen)

Elements
 Fundamental units of matter
Aristotle (350 B
...
): 5 elements (fire, earth, water, air, ether)
Dalton (1803): all matter is made of atoms
o Small, indivisible particles
o Smallest unit of matter that retains unique chemical properties
o Cannot be broken down in chemical reaction
o Each element has a unique name, atomic symbol, and atomic structure
o IUPAC (international union of pure and applied chemisty)-authority in naming
elements/compounds
Periodic Table of the Elements
 Rows are called “periods”
 Columns are called “groups”
o Group IA: alkali metals
o Group IIA: alkali earth metals
o Group VIA: chalcogens
o Group VIIA: halogens
o Group VIIIA: noble gases

Metals vs
...
11x10 g
 Proton (p+)
o Positive charge (+1 “elementary charge”)
o Mass=1
...
67x10 g

Neils Bohr
 Nucleus contains p+ and n0
 Electrons travel around nucleus in circular orbits (fixed energies)
# of protons determines type of element
 (atomic #) = # of P+
 For neutral atoms: # of e- = # of p+
 # of neutrons varies
Atomic notation
 Mass #: (# of p+) + (# of n0)
Isotopes
 Atoms of the same element w/ different # of neutrons
Ex
...
000
98
...
003
1

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