Atoms and the Periodic Table - Download as PowerPoint

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					Chapter 9
 Dmitri Mendeleev studied the properties of
  the 63 known elements in an attempt to
  organize them.
 He used an element’s melting point, density,
  color and atomic mass.
 Atomic Mass – the average mass of all the
  isotopes of that element.
 Mendeleev noticed that a pattern of
  properties appeared when he arranged the
  elements in order of increasing atomic mass.
 He found that the properties of the elements
  repeated.
 Mendeleev   called his arrangement of the
  elements a periodic table because of the
  repetition of properties.
 He left blank spaces in his table and
  predicted that these spaces would be fill by
  elements that had not yet been discovered.
 He was even able to predict the properties of
  those elements.
 The modern periodic table is arranged
  according to increasing atomic number.
 Nucleus – center of the atom and contains
  protons and neutrons.
 Protons – positively charge particles in the
  nucleus of the atom.
 Every atom of the same element has the
  same number of protons, which is called the
  atomic number.
 Neutrons – particles in the nucleus which
  have no charge (neutral)
 Protons and neutrons have about the same
  atomic mass and make up most of the mass
  of the atom.
 Electrons – particles moving around in the
  space around the nucleus which have a
  negative charge.
 Contains  information for each of the known
  elements.
 Contains the atomic number, chemical
  symbol, name and atomic mass for each
  element.
 Chemical Symbol – abbreviation of an
  element’s name. Its either one or two
  letters. Ex. – Fl or C
 The  periodic table is made up of rows called
  periods.
 The periodic table is made up of columns
  called groups or families.
 There are 7 periods and 18 groups.
 The properties of an element can be
  predicted from its location in the periodic
  table.
 Metals are shown on the left of the table
 Nonmetals are shown on the right of the
  table
 Metalloids are located between the metals
  and nonmetals.
 The pattern is repeated in each period and
  accounts for the fact that elements in the
  same group have similar characteristics.
 The  majority of the elements in the periodic
  table are metals.
 They are good conductors of electric current
  and heat.
 The metals begin on the left side of the table
  and extend most of the way across.
 The physical properties of metals include
  luster, malleability, ductility and
  conductivity.
A  material that has a high luster is shiny and
  reflective.
 A malleable material can be hammered or
  rolled into flat sheets.
 A ductile material can be drawn into long
  wires.
 Thermal conductivity is the ability of an
  object to transfer heat.
 The ability of an object to carry electric
  current is electrical conductivity.
 Reactivity – the ease and speed with which
  an element reacts with other substances.
 Metals usually react by losing electrons.
 Corrosion – the deterioration of a metal due
  to a chemical reaction in the environment.
 Metals   are classified as one of the following:
    Alkali metals
    Alkaline earth metals
    Transition metals
    Metals in mixed groups
    Lanthanides
    Actinides
 Group  1
 Most reactive metals in the periodic table
 Never found uncombined in nature because
  they are so reactive
 Low densities
 Low melting points
 Group  2
 Harder, denser and melt at higher
  temperatures than the alkali metals
 Highly reactive, but not as much as the alkali
  metals
 Group  3 – 12
 Most are hard and shiny solids with high
  melting points and high densities
 Less reactive than groups 1 and 2
 Some  of the elements in groups 13-16 are
  metals
 Two rows of elements placed below the main
  part of the table are the lanthanide and
  actinide metals
 Elements found after Uranium-92 are
  synthetic elements (man-made)
A  nonmetal is an element that lacks most of
  the properties of a metal.
 With the exception of hydrogen, nonmetals
  are found on the right side of the table.
 Most nonmetals are poor conductors of
  electric current and heat.
 Solid nonmetals tend to be dull and brittle.
 Nonmetals usually have lower densities than
  metals.
 For chemical properties, nonmetals usually
  gain or share electrons when they react with
  other atoms.
 There   are nonmetals in group 1 and groups
  14-18
 The families containing nonmetals are the
  following:
    Carbon family
    Nitrogen family
    Oxygen family
    Halogen family
    Noble gases
    Hydrogen family
 In group 14, only carbon is a nonmetal
 The nitrogen family has two, nitrogen and
  phosphorus
 The oxygen family has three, oxygen, sulfur and
  selenium.
 The halogens in group 17 are fluorine, chlorine,
  bromine and iodine. Halogens are very reactive
  and fluorine is the most reactive.
 The noble gases are in group 18. They are
  usually nonreactive.
 Hydrogen is not grouped with any family because
  its properties are so different.
 Elements  that have properties of metals and
  some of nonmetals are called metalloids.
 All metalloids are solid at room temperature,
  and are brittle, hard and somewhat reactive.
 Metalloids such as silicon, germanium and
  arsenic are used to make semiconductors,
  which are substances that can conduct
  electric current under some conditions but
  not under others.
 The idea of the atom dates back to 430 B.C.
 Today the atom is defined as the smallest
  particle that can still be considered an
  element.
 Atomic theory grew as a series of models
  that developed from experimental evidence.
  As more evidence was collected, the theory
  and models were revised.
   Dalton described the atom as the indivisible particle that
    makes up an element. He identified other characteristics
    of atoms, all of which remain part of the modern model.
   Thomson’s discovery of negatively charged particles called
    electrons disproved Dalton’s indvisible-atom idea. He
    proposed a model in which electrons were scattered
    throughout a ball of positive charge.
   Rutherford proposed the existence of a nucleus, a small,
    positively charged region of an atom containing positively
    charged particles that he called protons.
   Bohr revised the model to propose that electrons were
    found only in specific orbits around the nucleus.
   The modern cloud model suggests that an electron’s
    movement is related to its energy level, and electrons
    move rapidly within a cloudlike region around the nucleus.
 At the center of the atom is a tiny, dense
  nucleus containing protons and neutrons.
 Surrounding the nucleus is a cloudlike region of
  moving electrons.
 Almost all of the mass of an atom is
  concentrated in the nucleus.
 Protons have a charge of +1 and have a mass of 1
  amu.
 Neutrons have no charge and a mass of 1 amu.
 Electrons have a negative charge and a mass of
  1/2000 amu.

				
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