PPT

• Matter


  Anything that occupies space and has mass
• Substance


  A form of matter that has a definite composition and distinct properties
• Chemistry


  The study of matter and the changes it undergoes
• Mixture


  A combination of two or more substances in which the substances retain their distinct identities
• Types of mixtures

  • Homogeneous mixture - composition of the mixture is the same throughout
  • Heterogeneous mixture - composition is not uniform throughout
• Examples of mixtures

  • soft drink, solder
  • cement, iron filings in sand
  • Milk
• Physical means


  Can be used to separate a mixture into its pure components
• Examples of physical separation methods

  • magnet
  • distillation
• Element


  A substance that cannot be separated into simpler substances by chemical means
• Elements

  • 118 elements have been identified
  • 82 elements occur naturally on Earth
  • 36 elements have been created by scientists
• Examples of elements

  • gold, aluminum, lead, oxygen, carbon, sulfur
  • technetium, americium, seaborgium
• Compound


  A substance composed of atoms of two or more elements chemically united in fixed proportions
• Compounds


  Can only be separated into their pure components (elements) by chemical means
• Examples of compounds

  • lithium fluoride
  • quartz
  • dry ice – carbon dioxide
• Molecule


  An aggregate of two or more atoms in a definite arrangement held together by chemical forces
• Types of molecules

  • Diatomic molecule - contains only two atoms
  • Polyatomic molecule - contains more than two atoms
• Examples of diatomic molecules

  • H2, N2, O2, Br2, HCl, CO
• Examples of polyatomic molecules

  • O3, H2O, NH3, CH4
• Ion


  An atom, or group of atoms, that has a net positive or negative charge
• Types of ions

  • Cation - ion with a positive charge
  • Anion - ion with a negative charge
• Examples of ions

  • Na+, Cl-, Ca2+, O2-, Al3+, N3-
  • OH-, CN-, NH4+, NO3-
• Types of ions

  • Monatomic ion - contains only one atom
  • Polyatomic ion - contains more than one atom
• Common Ions Shown on the Periodic Table
• Ionic compounds


  Consist of a combination of cations and anions
• The formula is usually the same as the empirical formula
• The sum of the charges on the cation(s) and anion(s) in each formula unit must equal zero
• The most reactive metals (green) and the most reactive nonmetals (blue) combine to form ionic compounds
• Covalent bond


  Attraction between the nucleus of the 1st atom and the electrons of the 2nd atom; and the attraction of the nucleus of the 2nd atom and the electrons of the 1st atom. Sharing of electrons. Atoms of non-metals combine. Electronegativity difference is 0 to < 2.

  
• Electronegativity


  The ability of an atom to attract toward itself the electrons in a chemical bond
• Fluorine has the highest electronegativity
• Properties of covalent compounds

  Intermolecular forces of attraction is weak, gas, liquid or low-mp solid, insoluble in H2O (mostly), aqueous solutions do not conduct electricity
• Bond energy


  Amount of energy involved when bond is broken, amount of energy released when bond is formed, strong bond; ↑ bond energy
• Bond length


  Distance between the nuclei of atoms forming the bond, strong bond; ↓ bond length
• Bond order


  Number of bonds between atoms, single, double or triple, strong bond; ↓ bond length; ↑ bond order
• Ionic bond


  Attraction between cations and anions, atoms of metal and nonmetal combine, atoms with a large difference in electronegativities (≥2), metals lose electrons (cations), nonmetals gain electrons (anions) and the total net charge is 0
• Valence electrons


  The outer shell electrons of an atom that participate in chemical bonding
• Valence electron configuration by group

  • 1A - ns1
  • 2A - ns2
  • 3A - ns2np1
  • 4A - ns2np2
  • 5A - ns2np3
  • 6A - ns2np4
  • 7A - ns2np5
• Electron configuration


  How the electrons are distributed among the various atomic orbitals in an atom

  
• Order of orbitals (filling) in multi-electron atom: 1s < 2s < 2p < 3s < 3p < 4s < 3d < 4p < 5s < 4d < 5p < 6s
• Outermost subshell being filled with electrons