ATOMIC STRUCTURE

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ATOMIC STRUCTURE

• Structure and Transformation of Matter

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Subatomic Particles

• The atom is made up of smaller particles with
  measurable properties such as

MASS and ELECTRICAL CHARGES
PROTON ? define the identity
0NEUTRON0 ? related to isotope
-ELECTRON- ? define chemical properties
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Atomic Structure
Inner electron shell
Electron cloud
Proton
Nucleus
Neutron
Outer electron shell
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Subatomic Particles
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Atomic Number
All atoms of the same element have the same
number of p. The Atomic Number corresponds to
the number of p in the nucleus.
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Atomic Massalso called mass number
Atomic Mass is the number of protons and neutrons
in the nucleus
Atomic Mass p n0
18
8
8
18
Arsenic
75
33
75
Phosphorus
16
15
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Isotopes

• Atoms of the same element can have different
  numbers of neutrons.
• Thus, different mass numbers.
• These are called isotopes.

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Elements occur in nature as mixtures of isotopes.
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Solids, Liquids, gases

• Structure and Transformation of Matter

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How would you define MATTER?

• MATTER is anything that has

MASS
VOLUME
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Kinetic Molecular Theory

• The atoms, molecules that make up matter act like
  tiny particles that are always in MOTION.
• HIGHER the temperature of the substance, FASTER
  the particles move.
• at constant temperature, HIGHER the mass of the
  particles, SLOWER they move.

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Electrons and conductivity

• Structure and Transformation of Matter

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Ion Formation

• Electrons are in constant motion around the
  nucleus.
• Therefore ONLY electrons can be gained or lost.
• If an atom gains e-, it is a negatively charged
  ION.
• Conversely if an atom loses e-, it is positively
  charged ION.

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Conductivity

• Conductivity is directly related to the e-s
  ability to move freely.
• Metals are good conductors of heat and
  electricity because their atoms are held
  together by metallic bonds
• Chemical bond that is the result of positive
  metal ions surrounded by moving electrons

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• INSULATOR the electrons of nonmetal elements
  are more tightly bonded to their atoms, not
  allowing them to move from one place to another.
• Insulators include other materials such as wood,
  rubber, pure water, plastic, foam, glass, and air
• SEMICONDUCTOR an element or compound that has
  conductive properties b/t those of conductors and
  insulators.
• Metalloids such as Germanium, Silicon
• SUPERCONDUCTORmaterials through which current
  can flow indefinitely b/c, under certain
  conditions low Tº, they have no resistance to
  the flow of e-

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Elements and periodic table

• Structure and Transformation of Matter

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• All matter is made of substances called

ELEMENTS
Cannot be broken down into simpler substances by
CHEMICAL MEANS
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What is the smallest unit of a chemical element
that has the properties of that element?

• ATOM

The properties of each element are determined by
the structure of its atoms.
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Navigating the Periodic Table

• The rows are the periods
• The 7 periods are numbered starting with 1 at the
  top
• Each period starts a new shell of electrons.
• The columns are the groups
• The 18 groups are numbered starting with 1 at the
  left
• Each group has similar chemical properties
• Elements with similar properties have the same
  number of e- in the outermost shell valence e-

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How Are Elements Classified?

• All elements are either
• metals,
• nonmetals, or
• semiconductors metalloids.

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• Most are GASES except liquid Bromine
• BRITTLE in solid phase
• DULL ? neither shiny, nor bright
• Poor CONDUCTORS of heat and electricity
• Tend to GAIN e- in chemical rx

• SOLID at room temp. except liquid Hg
• MALLEABLE ? easily hammered into shape
• DUCTILE ? can be drawn into wire
• LUSTROUS ? shiny most
• High CONDUCTIVITY ? good conductors of heat and
  electricity
• Tend to LOSE e- in chemical reactions

• Fall along the jagged line separating metals and
  nonmetals except for Al
• B, Si, Ge, As, Sb, Te, Po

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Families Alkali Metals

• 1st column on the periodic table (Group 1).
• Very reactive metals with only 1 valence e-
• Combine easily with nonmetals to form salts.
• Reactivity increases with increasing atomic number

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Families Hydrogen

• First element in Group 1 b/c it has also one
  valence e- ,
• but Hydrogen belongs to a family of its own.
• Hydrogen is a diatomic, reactive gas.

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Families Alkaline Earth Metals

• 2nd column (Group 2)
• Highly reactive but slightly less than Group 1
• Have 2 valence e-
• Reactivity increases with increasing atomic number

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Families Transition Metals

• Elements in groups 3-12
• Less reactive, harder metals with high melting
  points
• Have the distinctive property to form colored
  ions.(e.g. Cu2 is blue-green)

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Families Halogens

• Elements in Group 17
• Very reactive, volatile, diatomic nonmetals
• Reactivity increases as atomic number decreases
• Reacts with alkali metals to form salts NaCl
• Exist in 3 phases F, Cl are gases, Br is liquid,
  and I, At are solids.

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Families Noble Gases

• Elements in Group 18
• VERY unreactive, but not inert since 1962, with
  the exception of He, all noble gases can form
  compounds under extreme conditions
• Monatomic gases
• Have a full valence shell.

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Compounds and physical properties

• Structure and Transformation of Matter

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• Elements rarely occur in pure form in nature,
  like in the Earths crust. They generally occur
  in combination with other elements.
• COMPOUND a substance made up of two or more
  different elements joined by chemical bonds.
• Their physical properties differ from the
  properties of the elements that make up the
  compound. water is liquid at room Tº, but is
  made of 2 gases

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• COMPOUNDS important characteristics

• Definite composition
• Can be broken down into simpler substances by
  chemical means
• Can be identified by their physical properties

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• MOLECULE a group of atoms that are held
  together by chemical forces.
• the smallest unit of a compound that has all the
  properties of the compound.
• composition shown in a chemical formula

Hydrogen peroxide H2O2
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What are PHYSICAL properties?

• Properties that can be observed without changing
  the identity of the substance.
• mass, volume, color, shape, size, texture,
  odor, melting point, boiling point, density,
  polarity, hardness, conductivity.

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Molecular interactions

• Chemical bonds hold atoms together in molecules,
  while intermolecular forces hold molecules
  together
• Those forces determine the physical properties
  of a compound
• Greater those forces, tighter the substances are
  held together, leading to
• higher melting point
• higher boiling point

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POLARITY

• Polarity is one factor affecting the strength of
  those intermolecular forces
• polarity occurs when one end of the molecule has
  a slight positive charge and the other has a
  slight negative charge.
• the attractive forces between polar molecules
  tend to be strong

Methyl chloride CH3Cl
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Chemical bonding and compounds

• Structure and Transformation of Matter

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Chemical BondsIonic Bonds

• Attractive force between oppositely charged ions,
  forming when e- are TRANSFERRED from one atom or
  molecule to another
• Atoms seek to have a total of 8 e- in the outer
  energy levels octet rule.

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• Elements whose atoms have only one, two, or
  three valence electrons tend to lose electrons
  easily.
• Elements whose atoms have from five to seven
  valence electrons are more likely to gain
  electrons.

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Chemical BondsCovalent Bonds

• Forming when atoms SHARE one or more pairs of
  electrons.
• Covalent bonds are most likely to form between
  elements whose atoms have four, five, six, or
  seven valence e-

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Chemical BondsTypes of covalent bonds
NON-POLAR bond when two exact non-metals
equally share electrons. Example Hydrogen
atoms sharing e-
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Two atoms of ?
FLUORINE
A molecule of Fluorine
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Chemical BondsTypes of covalent bonds
POLAR bond when two different non-metals
share electrons. Example Water molecule
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Chemical reactions and reaction rates

• Structure and Transformation of Matter

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Chemical Reactions
PRODUCTS
REACTANTS
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4 MAIN Signs of a Chemical Rx

• Formation of a precipitate or change in
  solubility

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4 MAIN Signs of a Chemical Rx

• Color change

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4 MAIN Signs of a Chemical Rx

• Gas formation

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4 MAIN Signs of a Chemical Rx

• Temperature change

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Other signs of a Chemical Rx

• Odor change
• Light emission without heat
• Volume change
• Conductivity change
• Melting or boiling point change
• Any other change in physical or chemical
  properties of the reactants.

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Combination or Composition or Synthesis Reactions
A B ? AB Iron Oxygen ? iron oxide rust
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Decomposition Reaction
AB ? A B Water ? Hydrogen Oxygen
electrolysis
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Single Replacement Reaction
A BC ? AC B Iron copper sulfate ? iron
sulfate copper
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Double Replacement Reaction
AB CD ? AD BC Iron chloride potassium
sulfide ? potassium chloride iron sulfide
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Combustion (oxidation) Reaction
burning in air or oxygen Carbon oxygen ? carbon
dioxide
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Reaction Rate The Collision Theory

• Reaction rate refers to the SPEED at which
  reactants change into products
• The collision theory states that for a chemical
  reaction to take place,
• the atoms must come together with the proper
  orientation to form new bonds, but also
• with enough energy to effect a change

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ORIENTATION
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Factors affecting Reaction Rate

• Any factor that would increase the collisions
  with the right orientation and sufficient energy
  will increase the reaction rate
• Higher TEMPERATURE
• Higher PRESSURE especially for gases
• Higher CONCENTRATIONe.g. burning coal with pure
  oxygen instead of air -20O2-
• Presence of a CATALYST accelerates the reaction
  without being changed or used up.

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Energy and chemical reactions

• Structure and Transformation of Matter

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• Energy is always required to break bonds, but
  energy is also released when new bonds are formed
• Chemical reactions can either be
• exothermic energy being released or
• endothermic energy being absorbed
• What makes the overall reaction exothermic or
  endothermic is determined by whether more energy
  is released or absorbed.
• The products may have less or more potential
  energy than the reactants

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EXOTHERMIC
ENDOTHERMIC
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