Chapter 3 Matter and Atomic structure

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Chapter 3- Matter and Atomic structure

• Matter-
• Makes up the physical world and living things
  around us. On Earth, found on 3 states solid,
  liquid or gas.
• Elements- (118 known, 92 occur naturally)
• Substance that cannot be broken down into simpler
  substances by physical or chemical means, while
  maintaining characteristics.
• Each has a symbol and unique characteristics.

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Chapter 3 - Atoms

• Atoms- Make-up Elements
• Smallest particle of an element that has all its
  characteristics.
• 3 types of particles
• Protons, neutrons electrons
• Protons () and neutrons (no charge) both have a
  similar mass and are at the atoms center (the
  nucleus). Thus, the nucleus has mass, and has a
  positive charge.
• Electrons (-) are in the periphery, in energy
  levels. Little mass, so virtually all atoms mass
  is from protons and neutrons.

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Atoms 2

• Atomic number The number of protons.
• Atoms Mass number Number of protonsneutrons
  (e- have little mass)
• Atoms electric charge No overall charge
  (neutral- same number of electrons and protons,
  with same magnitude of charge)
• Size of an atom Depend on number and arrangement
  of electrons
• Energy levels Area of an atom where electrons
  are found (often called shells)

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Energy Levels (and electrons within)

• The very general rule (see later for clues on
  using)
• 1st- 2 e- 2nd- 8 e-
• 3rd- 18 e- 4th- 32 e- / (up to seven known)
• __________________________________________________
  _____
• The number of the energy level (1st, 2nd, 3rd,
  4th, etc.) is the Principal Quantum Number, n.
  The greatest number of e- at any level is given
  by 2n2. Thus, level 4th can have up to 2(4)2 32
  electrons.
• Electrons tend to occupy the lowest level. As
  each level fills up, additional e- go to the next
  level ?? The lower shells will always be full,
  but the last one may not. In inert elements, the
  last level is full they do not easily combine
  with other elements.
• Valence electrons The number of e- on the
  outermost level. Determine elements chemical
  behavior.

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Energy Levels (and electrons within)Practical
clues for usage

• Electron subshells- Each energy level (1st to the
  maximum for an element) has subshells, areas
  where e- are likely to be found.
• The subshells are s, p, d, f
• A specific number of e- fit into each subshell
• s?2e- p?6e- d?10e- f?14e-
• - However, the energy levels (and subshells
  within) have a specific order of filling with e-.
  Electrons dont go into the next higher energy
  level until all the lower levels (with their
  subshells) have already been filled
  ???(continues with the order)

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Filling order of Energy Levels Subshells

• 1s
• 2s 2p
• 3s 3p 3d
• 4s 4p 4d 4f
• 5s 5p 5d 5f
• 6s 6p 6d
• 7s 7p

• Examples
• Maximum per subshell
• s?2e- p?6e- d?10e- f?14e-
• 1- Magnesium (Mg) 12
• 1s2 2s2 2p6 3s2
• 2- Calcium (Ca) 20
• 1s2 2s2 sp6 3s2 3p6 3d2
• 3- Krypton (Kr) 36
• 1s2 2s2 2p6 3s2 3p6 3d10 4s2 4p6

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More Periodic Table Reasoning

• Periods (7)- Horizontal rows (increasing atomic
  number). The row beginning with Cerium (Ce)
  belongs in period 6, and the row beginning with
  Thorium (Th) belongs with period 7.
• Groups or Families (8 in some classifications)
  Vertical rows. (Groups elements with similar e-
  configurations (with exceptions H and He).
• Noble gases Inert because they have filled the
  outer shell (last column on right, from He to
  Uuo)
• Metals (Blue on your book). Solid at room
  temperature (except Mercury, Hg) conduct heat
  and electricity, are malleable and ductile, and
  are shiny.
• Non-metals (Yellow in your book). The opposite
  characteristics (non-conductors, etc.). Some
  gases, some solids, one is liquid (Bromine, Br)
• Metalloids (Green in your book). Have the
  appearance of metals, but have non-metal
  properties (brittle, non-conductive)

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Isotopes

• - All atoms of an element have the same of
  protons and electrons. However, they can differ
  in the number of neutrons. These are isotopes of
  that element. Since neutrons have mass, some
  isotopes are heavier and some lighter
  (different mass number).
• - Many elements occur as more than one isotope.
  The atomic mass of an element is the average of
  the mass numbers of the isotopes of that element.
• Some elements have nuclei that are unstable.
  Radioactivity- the spontaneous process by which
  radiation is emitted from unstable nuclei (three
  types of emission - loosing protons and
  neutrons
• - change a proton to a neutron
• - change a neutron to a proton
• Most isotopes are not radioactive, but some
  are.

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Elements, Molecules, Compounds- The Periodic Table

• - Elements
• Atomic number 12 (e- in shells 2, 8, 2)
• Symbol Mg
• Atomic mass 24.30 amu (atomic mass units)
• - Molecule a substance composed of two or more
  atoms held together by covalent bonds.
• - The atoms can be of the same element (ex.
  O2), or
• - The atoms can be of different elements (ex.
  H2O, CO2)
• - Compound A substance composed of atoms of two
  or more elements that are chemically combined.
• - Substance Non-descriptive term. Can be
  element, molecule, or compound.
• - Collision Theory Molecules must collide to
  react, and the greater the number of collisions
  per second, the greater the reaction rate.
• - Chemical reaction The change of one or more
  substances into other substances.

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Collision theory

• In order for a chemical reaction to occur
  between 2 molecules, the two molecules must
  collide with each other. The rate of the reaction
  is proportional to the number of collisions
• (The more collisions that occur, the faster the
  reaction)