WELCOME TO AP CHEMISTRY

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WELCOMETO AP CHEMISTRY

• MAHUA CHAKRABORTY

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What is Matter

• Matter is anything that has mass and takes up
  space.
• Examples are rockets, paper, notebook, a car.

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Atoms and Elements

• Smallest particle of any element is called an
  atom.
• An element is a substance composed of only one
  kind of atom. Each element is represented by a
  chemical symbol made up of one or two letters.
• Example for one letter elements are Hydrogen H,
  Nitrogen N ..
• Example for two letter elements are Magnesium
  Mg, Calcium Ca, Silicon Si.

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The Nuclear Atom

• Atoms are made up of subatomic particles called
  electrons, protons, and neutrons.
• Protons and Neutrons form a compact, central body
  which is the nucleus of the atom.
• Electrons are like a cloud around the nucleus.
• Protons are positively charged and electrons are
  negatively charged.
• Neutrons however dont have any charge.

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• Nuclear atom

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• The number of protons in an atomic nucleus is
  called the atomic number.
• It is denoted by Z.
• There is an equal number of electrons surrounding
  the nucleus.
• The atom has no charge.
• The total number of protons and neutrons is
  called the mass number .
• This is denoted by A.
• Neutrons and protons jointly are called nucleons.

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Isotopes

• Atoms with same atomic number but with different
  mass numbers are called isotopes.
• An isotope is named by writing its mass number
  after the name of the element, as in
  neon-20,neon-21,and neon 22.
• Symbol is written by adding the mass number as a
  superscript to the left of the chemical symbol of
  the element e.g.20Ne,21Ne,and 22Ne.

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• Carbon isotopes

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Properties Of Isotopes

• Isotopes of the same element have the same number
  of protons and the same number of electrons they
  have essentially the same properties.
• An exception of this is hydrogen. The mass
  differences between isotopes are relatively
  large. As a result hydrogen isotopes have
  differences in the properties.
• Examples of isotopes of hydrogen are
  Deuterium(2H) and Tritium(3H).

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Class Practice

• How many protons, neutrons and electrons are
  present in a) an atom of nitrogen-15 b) an atom
  of iron-56.
• Write the symbols of the isotopes of a) argon b)
  calcium that have the same number of neutrons as
  40K.

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The Periodic table

• The periodic table is made up of vertical columns
  called groups and horizontal rows called periods.
• The members of each group show similarity with
  one another.
• The 1st group is the alkali metals.
• The 2nd group is the alkaline earth metals.
• Groups 3-11 contain the transition metals.
• Groups 12,13 and 14 are the having less active
  metals. E.g. Pb and In.
• Group 17 constitutes the halogen group.
• Group 18 constitutes the noble gas.

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• The long block shown below the main table is the
  inner transition metals.
• Elements in the upper row begins with lanthanum
  so it is called the lanthanides.
• Elements in the lower row begins with actinium
  hence it is called as actinides.

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Metals, Nonmetals and Metalloids

• Metals conduct electricity, has a metallic luster
  and is malleable and ductile e.g. Na, Cu, and Au.
• Nonmetals do not conduct electricity and is
  neither malleable nor ductile e.g. S, C, and P..
• Metalloids has the appearance and some physical
  properties of a metal but behaves chemically like
  a nonmetal e.g. Ge, Si..

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• Part of the periodic table.

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What are Compounds

• Compound is a substance that consists of two or
  more different elements with their atoms in a
  definite, characteristic ratio.
• Two types of compounds Organic and inorganic
  compounds.
• Organic compounds are compounds containing Carbon
  and Hydrogen.
• Inorganic compounds include water, ammonia,
  hydrochloric acid etc.

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Molecules

• Molecule is a definite electrically neutral group
  of atoms bonded together e.g. H2O.
• All gaseous elements are found as diatomic
  molecules. e.g. O2 , Cl2.

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Formulas

• Chemical Formula tells us which element is
  present and the subscript tells us how many atoms
  of that element is present. e.g. O2 ,S8 and P4.
• Structural Formula represents the atoms by their
  elemental symbols and use lines to show which
  atoms are joined together.
• E.g.

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Models

• Ball and Stick Model
• The colored balls depict the atoms and the sticks
  indicate the links between them.

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• Tube Structure
• This structure omits the balls and represents the
  atoms and the links between them by colored
  lengths of tube.

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Ions and Ionic Compounds

• Ionic compounds consists of positive and negative
  ions held together by the attraction between
  their opposite charges. E.g. Sodium chloride
  consists of alternate Na and Cl ions.
• Positively charged ions are called cations and
  negatively charged ions are anions.
• Na means sodium atom that has lost one electron
  and hence has a single positive charge.
• Cl- means chlorine has gained an electron that
  increases the negative charge by one atom.

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Chemical Formulas Of Ionic Compounds

• Ionic compounds does not consist of individual
  molecules.
• Ratio of the number of cations to the number of
  anions is the same for any sample of a given
  compound we can use that ratio to write its
  formula.
• In sodium chloride there is one Na cations for
  each Cl- ion, so its formula is NaCl.

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• Examples of poly atomic cations ammonium ion
  NH4.
• Polyatomic anions are called oxo anions e.g.
  CO32-
• Formula unit is a group of ions with a
  composition given by the formula of an ionic
  compound.
• Formula unit for NaCl consists of one Na and one
  Cl- ion. For ammonium sulfate consists of two
  NH4 ions and one SO42-ion.

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Class Practice

• Identify the type of each substance and give the
  number of atoms of each element in the formula
  units or molecules of the compounds a)N2O4
• b)(NH4)3PO4 c)P4

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Mixtures

• Elements and Compounds are pure substance.
• Mixtures are simple substance which are neither
  element nor compounds.
• Gasoline is a mixture of hydrocarbons and
  additives blended together to achieve efficient
  combustion.
• Alloys are mixtures of metals formulated for
  maximum strength and resistance to corrosion.

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Mixture And Compounds

• Mixtures
• Compounds can be separated by using physical
  techniques.
• Composition is variable.
• Properties are related to those of its components

• Compounds
• Components cannot be separated by using physical
  techniques.
• Composition is fixed.
• Properties are unlike those of its components

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Types Of Mixtures

• Heterogeneous
• In this type we can identify the different
  components of the mixture.
• Examples are sand and sugar
• Milk if seen through microscope you can see
  individual globules of butterfat.

• Homogenous
• In this type the individual components cannot be
  separated
• Example syrup of sugar and water.
• White vinegar.

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Separation techniques

• To analyze the composition of a sample that we
  suspect is a mixture we need to separate its
  components.
• Filtration Makes use of differences in
  solubility. The sample is shaken with a liquid
  and then poured through a mesh, the filter. You
  can separate the soluble material that passes
  through the filter and the insoluble is captured
  by the filter.

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• Distillation This technique makes use of the
  difference in the boiling points. Can be used to
  separate two liquids having different boiling
  point or a mixture of a salt and water where the
  boiling point of the salt is much higher than the
  boiling point of water.

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• Distillation

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• Chromatography This technique depends on the
  different abilities of substances to adsorb or
  stick to surfaces. The mixture is washed across a
  strip of filter paper. Substances that adsorb
  weakly move far apart than others. Colored
  components give rise to separate patches of color
  on the paper.

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• Paper chromatography

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Molecular Compounds

• Binary molecular compounds are built from 2
  elements.
• Example Phosphorus trichloride PCl3 and carbon
  monoxide CO.
• The oxo acids are molecular compounds that are
  the parents of oxo anions e.g. sulfuric acid is
  the molecular compound.SO42- has 2 negative
  charges. To balance this two H ions are needed.

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Class Practice

• Give the systematic names of the compounds a)
  N2O4 b)ClO4