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Unit 2 Chemistry

Unit 2 Chemistry. Atomic Mass and Isotopes. While most atoms have the same number of protons and neutrons, some don’t. Some atoms have more or less neutrons than protons. These are called isotopes.

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Unit 2 Chemistry

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  1. Unit 2 Chemistry

  2. Atomic Mass and Isotopes • While most atoms have the same number of protons and neutrons, some don’t. • Some atoms have more or less neutrons than protons. These are called isotopes. • An atomic mass number with a decimal is the total of the number of protons plus the average number of neutrons. • We write isotopes like this: • Uranium has 2 isotopes: Uranium – 238 & Uranium - 239 U U Mass # 238 239 92 Atomic # 92

  3. Isotope Examples List the protons, neutrons, electrons and the symbol • Carbon – 12 • Carbon – 13 • Carbon – 14 • Note: • The # of neutrons may vary. • Isotopes have different mass numbers. • Isotopes of the same element are still chemically alike because they have the same number of protons and electrons.

  4. Properties of Metals • Metals are good conductors of heat and electricity. • Metals are shiny. • Metals are ductile (can be stretched). • Metals are malleable (can be pounded into thin sheets). • A chemical property of metal is its reaction with water which results in corrosion.

  5. Properties of Non-Metals • Non-metals are poor conductors of heat and electricity. • Non-metals are not ductile or malleable. • Solid non-metals are brittle and break easily. • They are dull (not shiny). • Many non-metals are gases. Sulfur

  6. Properties of Metalloids • Metalloids (metal-like) have properties of both metals and non-metals. • They are solids that can be shiny or dull. • They conduct heat and electricity better than non-metals but not as well as metals. • They are brittle and not ductile Silicon

  7. A Family is also called a Group.

  8. based on their atomic numbers.

  9. Columns of elements are called groups or families. Elements in each family have similar but not identical properties. All elements in a family have the same number of valence electrons. Each horizontal row of elements is called a period. The elements in a period are not alike in properties. In fact, the properties change greatly across even given row. The first element in a period is always an extremely active solid. The last element in a period, is always an inactive gas. The period tells us how many orbitals the element has. Periods Groups or Families

  10. Groups of the Periodic Table • Alkali Metals: Group 1 • Soft, shiny metals • Good conducters • Very reactive • Will produce a coloured flame when heated • Excluding H – a diatomic molecule • Li - lithium Rb - rubidium • Na – sodium Cs - caesium • K - potassium Fr – francium

  11. Groups • Alkaline Earth Metals – group 2 • Have 2 valence electrons • Most are white in colour • Be – beryllium • Mg – magnesium • Ca – calcium • Sr – strontium • Ba – barium • Ra – radium (not always considered an alkaline earth due to its radioactivity)

  12. Groups • Group 3 - 12: Transition Elements • Elements that have an incomplete subshell • Group 13: Boron Group • These elements are characterized by having 3 electrons in the outer energy level (valence) • Group 14: Carbon Group • These elements are characterized by having 4 electrons in the outer energy level • these elements share their electrons, the tendency to lose electrons increases as the size of the atom increases, as it does with increasing atomic number

  13. groups • Group 15 Nitrogen group • These elements are characterized by having 5 electrons in the outer energy level (valence) • Group 16 Oxygen group) • These elements are characterized by having 6 electrons in the outer energy level (valence) • Group 17 Halogens • The term halogen was coined to mean elements which produce a salt in union with a metal • The elements are characterized by having 7 electrons in the outer energy level (require 1 more electron)

  14. Noble Gases • Noble Gasesare colorless gases that are extremely un-reactive. • One important property of the noble gases is their inactivity. They are inactive because their outermost energy level is full. • Because they do not readily combine with other elements to form compounds, the noble gases are called inert. • The family of noble gases includes helium, neon, argon, krypton, xenon, and radon. • All the noble gases are found in small amounts in the earth's atmosphere.

  15. Assignment • Families of the Periodic Table worksheet In computer lab

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