Chem Unit 3

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lrsimon
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55258
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Chem Unit 3
Updated:
2010-12-12 13:03:48
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Chem semesters
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The Periodic Table and Periodic Properties
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  1. Historical Development of the Periodic Table:
    • Antoine Lavoisier compiled a list of all elements that were known in that time and organized them into 4 categories.
    • John Newlands proposed the law of octaves that if the elements were organized by increasing atomic mass then their properties repeated every eighth element.
    • By arranging the elemnets in order of increasing atomic mass into columns with similar properties, Mendeleev and Meyer organized the elements into a periodic table.
    • As elements and their properties were discovered it was apparent that Mendeleev's table was not completely correct.
    • Moseley's arrangements by atomic number resulted in a clear periodic pattern of properties. This pattern is not the periodic law.
  2. Periodic Law:
    The statement that there is a periodic repetition of chemical and physical properties of the elements when they are arranged in increasing atomic number.
  3. The modern periodic table:
    The modern periodic table consists of boxes, each containing the element's name, symbol, atomic number, and atomic mass. The boxes are arranged in increasing atomic number into series of columns called groups or families, and rows called periods.
  4. Metals:
    • Elements that are generally shinny when smoth and clean, solid at room temperature, and good conductors of heat and electricity.
    • most representative (1, 2, 3, 13-18) and transition elements (3-12) are metals.
  5. Alkali Metals:
    The group 1 elements except hydrogen are alkali metals. These are very reactive (sodium, lithium).
  6. Alkaline Earth Metals:
    These are in group 2. They are also highly reactive (calcium, magnesium).
  7. Transition and Inner transition metals:
    • The transition elements are divided into transition and inner transition metals.
    • The inner transition metals are divided into:
    • Lanthanide series: substances that emit light when struck by electrons.
    • Actinide series: along with the lanthanide series these are located in the bottom of the periodic table.
    • The rest of the elements from 3-12 are transition metals.
  8. Nonmetals:
    • These occupy the upper right side of the periodic table.
    • These are element that are generally gases or brittle, dull-looking solids.
    • They are poor conductors of electricity and heat.
  9. Halogens:
    These are highly reactive and occupy group 17 in the periodic table (fluorine).
  10. Noble Gases:
    • The extremely unreactive group 18 elements are called noble gases.
    • They are used in lasers, light bulbs, and neon signs.
  11. Metalloids:
    • These are the elements bordering the stairstep except aluminum.
    • They have chemical and physical properties of both metals and nonmetals (silicon, germanium).
  12. Octet Rule:
    states that atoms tend to gain, lose or share electrons in order to acquire a full set of eight valence electrons and reach stability.
  13. Atomic size:
    • generally decreases from left to right and increases as you go down in a group.
    • atomic size is defined by how closely an atom lies to a neighboring atom. atom size varies from one substance to another.
  14. Ionic size:
    • Atoms can gain or lose electrons to form ions.
    • Ion: an atom or a bonded group of atoms that has a positive or negative charge.
    • When ant atom loses electrons and form positively charged ions, they become smaller.
    • Positive ions are smaller than the neutral atom from which they formed
    • Negative ions are larger than the neutral atom from which they formed.
    • from left to right positive ions decrease and from 15 or 16 the size of large ions decrease.
  15. Ionization energy:
    is defined as the energy required to remove an electron from a gaseous atom.
  16. Electronegativity:
    • indicated the relative ability of its atoms to attract electrons in a chemical bond (same trend as ionization energy)
    • noble gases do not have electronegativity
  17. Inner transition:
    • Position:
    • •The Inner Transition Metals are present
    • in the bottom of the Periodic Table.
    • •They occupy periods 6 and 7.
    • •They are divided into two series, lanthanoid and actinoids.
    • •The lanthanoid series consists of 14 elements which starts from cerium to lutetium.
    • •Actinoids consists of 14 elements from thorium to lawrencium (atomic #: 90-103)
    • Common properties of lanthanides:
    • •They are strong reducing agents.
    • •Their compounds are generally ionic.
    • •At elevated temperatures, ignite and burn vigorously.
    • •Strongly paramagnetic.
    • •Fluoresce strongly under ultraviolet light.
    • •Lanthanide ions tend to be pale colors
    • •The magnetic moments of the lanthanide and iron ions oppose each other.
    • •The lanthanides react readily with most nonmetals and form binaries.
    • •The coordination numbers of lanthanides
    • are high(<6).
    • Common properties of rare earth (both)
    • •The rare earths are silver, silvery-white, or gray metals.
    • •The metals have a high luster, but tarnish readily in air.
    • •The metals have high electrical conductivity.
    • •The rare earths share many common properties. This makes them difficult to separate or even distinguish from each other.
    • •There are small differences in solubility and complex formation between the rare earths.
    • •The rare earth metals naturally occur together in minerals.
    • •Rare earths are found with non-metals
    • •There is little tendency to vary the valence.

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