Introductory Chemistry

1
Types of Matter
2
Pure Substances

• Elements-simplest pure substances, everything
  else is made from these. Smallest unit is the
  atom.
• Compounds combinations of atoms in fixed
  proportions. Cannot be separated by physical
  means, but can by chemical means.

3
Mixtures

• Can separate by physical means.
• Homogeneous uniform composition, these are
  solutions.
• Heterogeneous uneven composition.

4
Physical Properties

• Physical properties
• -those that do not involve change in
  composition. Subdivided
• Extensive - depend on amount of matter, e.g.
  mass, volume
• Intensive independent of amount of matter,
  e.g. melting point, density.
• These can identify substances

5
Chemical Properties

• These that do involve a change in composition,
  e.g. oxidation, decomposition, combustion.

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Atoms Elements

• Elements-simplest pure substances, everything
  else is made from these.
• Cannot separate by physical means but can by
  chemical means. Smallest unit is the atom.
• Elements given symbols - either single upper case
  letter or an upper case letter followed by a
  lower case one.
• E.g. C is carbon, O is oxygen, Co is cobalt.

7
Atoms Elements II

• Compounds-also pure substances, made from
  combinations of atoms from two or more elements
  in fixed proportions
• Cannot separate by physical means, but can by
  chemical means. Smallest units are molecules or
  formula units.
• Compounds given formulas that show how many of
  each type of atom is present.
• E.g. CO is carbon dioxide.

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Daltons Atomic Theory

• 1. Matter composed of small, indivisible
  particles called atoms.
• 2. All atoms of one element are alike, but
  differ from atoms of other elements.
• 3. Compounds form when atoms of different
  elements combine in fixed proportions.
• 4. A chemical reaction involves a rearrangement
  of atoms.

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Cathode Rays
Cathode rays are the carriers of electric current
from cathode to anode inside a vacuumed
tube Cathode rays have the following
characteristics Emit from the cathode when
electricity is passed through an evacuated
tube Emit in a direction perpendicular to the
cathode surface Travel in straight lines Cause
glass and other materials to fluoresce Deflect in
a magnetic field similarly to negatively charged
particles
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Canal Rays II

• If traces of a gas are left in a tube, positive
  rays called canal rays are produced.
• They can be deflected like cathode rays but in
  the opposite direction the larger the atomic
  mass of the gas the less they are deflected.
• They are atoms that have lost an electron.

11
Nuclear Atoms

• Mass values for atomic particles and atoms are
  based on the atomic mass unit (amu), defined as
  1/12 the mass of an atom of carbon-12, see
  isotopes below.
• Particle Symbol Mass Charge Site
• Proton p 1 1 Nucleus
• Neutron no 1 0 Nucleus
• Electron e- .0005 -1 Outside nucleus

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Nuclear Arithmetic

• Atomic number (Z) number of protons, all atoms
  of an element have the same Z. Neutral atoms
  have the same number of electrons as protons.
• Mass number (A) sum of number of protons and
  neutrons in an atom.
• The number of neutrons is A Z

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Isotopes

• Most elements have atoms with different numbers
  of neutrons, therefore different A values These
  called isotopes. AZX
• Chlorine has two isotopes with A values 35 and
  37
• 3517Cl (chlorine-35) and 3717Cl (chlorine-37)

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Atomic Mass

• An average value for the mass of an atom in amu
  based on relative amounts of each isotope.
• Though strictly speaking incorrect, this is
  commonly termed atomic weight.
• Chlorine 75.0 of atoms are chlorine-35 and
  25.0 chlorine-37
• The average atomic mass is obtained-
• Av.M. (35.0 x .750) (37.0 x .250) 35.5

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Atomic Structure

• Atoms excited by heat or electricity emit light
  of characteristic color (neon lights), several
  colors.
• - color due to frequency of light, blue is high -
  high frequency means high energy.
• - Bohr said electrons placed in "orbits" around
  nucleus
• - as they fall from one level to a lower one they
  emit light
• - only certain frequencies emitted, so only
  certain orbits or energy levels exist.

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The Bohr Model
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Energy Levels

• Each energy level holds a definite maximum number
  of electrons Where n is number assigned to
  level e- 2n2 E.g. for level 3 e-
  2(32) 18
• Each level is called a shell and has one or more
  sub-shell and each sub-shell has one or more
  orbitals, finally each orbital can hold a maximum
  of two electrons.

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Shells, Sub-shells Orbitals

• Shell Sub-shells Orbitals Electrons Shell Total
• 1 1s 1 2 2
• 2 2s 1 2
• 2p 3 6 8
• 3 3s 1 2
• 3p 3 6
• 3d 5 10 18
• 4 4s 1 2
• 4p 3 6
• 4d 5 10
• 4f 7 14 32

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Electron Placement

• Electrons placed from lowest levels up according
  to the value of Z with 1s being the lowest energy
  level then 2s, 2p etc., but the energy level for
  3d is higher than that for 4s which results in
  this being filled first. Beyond this there are
  more overlaps but we do not cover that here. The
  orbitals have distinctive shapes and this in turn
  leads to distinctive shapes for molecules.

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Electron Configurations

• Element Shell 1 Shell 2 Shell 3 Shell 4 Orbital
  config.
• H 1e- 1s1
• He 2e- 1s2
• Li 2e- 1e- 1s22s1
• Be 2e- 2e- 1s22s2
• B 2e- 3e- 1s22s22p1
• C 2e- 4e- 1s22s22p2
• N 2e- 5e- 1s22s22p3
• O 2e- 6e- 1s22s22p4
• F 2e- 7e- 1s22s22p5
• Ne 2e- 8e- 1s22s22p6
• Na 2e- 8e- 1e- 1s22s22p63s1
• Mg 2e- 8e- 2e- 1s22s22p63s2
• Al 2e- 8e- 3e- 1s22s22p63s23p1
• Si 2e- 8e- 4e- 1s22s22p63s23p2
• P 2e- 8e- 5e- 1s22s22p63s23p3
• S 2e- 8e- 6e- 1s22s22p63s23p4
• Cl 2e- 8e- 7e- 1s22s22p63s23p5
• Ar 2e- 8e- 8e- 1s22s22p63s23p6

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Electron Configurations III

• s-block Groups 1A 2A.
• Valence electrons in s subshell
• p-block Groups 3A - 8A.
• Valence electrons in p subshell
• d-block Groups 3B 2B.
• Valence electrons in s subshell
• f-block Lanthanides Actinides.
• Valence electrons in f subshell

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Periodic Law

• Representative elements in the same group in the
  periodic table owe their similarities in
  properties to the fact that they all have the
  same number of electrons in the outermost shell.
  The group number is the same as the number of
  electrons in the outermost shell.

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General Locations
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Periodic Table I

• When elements were arranged in order of
  increasing atomic weight a pattern emerges in
  which elements with similar properties occur at
  definite intervals. Some irregularities occur,
  but these are removed by placing the atoms in
  order of atomic number this is now the basis for
  the modern periodic table.

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Periodic Table II

• 2. The columns are called groups. The ones with
  B in the number are called transition elements,
  they are all metals, and the Lanthanide and
  Actinide series are called inner transition
  elements. These will not be discussed in this
  class.

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Periodic Table III

• 3. The remaining groups are the representative
  elements and are numbered 1A through 8A (also
  sometimes 0). All the elements in one group have
  the same number of electrons in the outer
  (valence) shell which is the same as the group
  number. They also have the same electron
  configuration, this gives them many similar
  properties.

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Periodic Table IV

• 4.Some have names 1A - alkali metals, 2A -
  alkaline earth metals, 7A - halogens and 8A -
  inert (or noble) gases. From top to bottom in a
  group elements become more metallic in nature
• E.g group 4A C - nonmetal, Si - metalloid, Sn
  and Pb - metals.

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Periodic Table V

• 5.The rows are called periods and correspond to
  the valence shell of the elements. They change
  from left to right from metals to nonmetals.
• 6.A zigzag line to the left of B, Si, Te At
  separates metals from nonmetals.
• 7.Metals form ionic bonds with nonmetals (next
  chapter), they are shiny, conduct heat and
  electricity and are strong.

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Periodic Table VI

• 8.Nonmetals also form covalent bonds with each
  other, physical properties are varied, they do
  not conduct heat or electricity.
• 9. Metalloids are Si, Ge, As, Sb, Te, Po At.
  Their properties are intermediate between those
  of metals and metalloids.

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Periodic Properties I

• Atomic Radius Increases from top to bottom
  within a group. This is due to the electrons in
  outer shells being further from the nucleus.
  Decreases from left to right along a period. This
  is due to as more protons are added beyond a core
  of a completed period, the electrons are held
  more tightly by what is called the effective
  nuclear charge.
• Ions atoms can gain or lose electrons to get a
  noble gas configuration.

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Periodic Properties II

• Ionization energy energy required to remove an
  electron. Decreases down a group as the furter
  away from the nucleus the less tightly electrons
  are held. Increases, with a few irregularities,
  from left to right across a period because of the
  increased effective nuclear charge

32
Periodic Properties III

• Electron Affinity energy change when an atom
  gains an electron. Increases from left to right
  across a period in parallel with the effective
  nuclear charge. Top to bottom trends within a
  group are not consistent.