Key Concepts- Chemistry

• Ionic Bond


  Bond between a metal and non-metal. It has a strong electrostatic force of attraction between a positive and negative ion.
• Covalent Bonding


  Between two or more non-metals. Sharing a pair of electrons between 2 nuclei
• Metallic Bonding


  Bond in metals
• Cations-> Positively charged ions
• Anions-> Negatively charged ions
• Ionic Bonds form lattice structures
• Lattice


  in layers
• 2 types of covalent bond:

  -simple molecular (made of few atoms)

  -giant covalent (made of millions of atoms: diamond, graphite)
• Properties of Simple Covalent

  -low melting and boiling points

  -doesn't conduct electricity (there isn't free flowing electrons)

  -flammable
• delocalised electron


  free electron
• Metallic bonds have strong force of attraction between cations+ the delocalised electrons. Form giant lattice structures.
• alloys-> mixture of metals
• Diamond

  -very hard

  -high melting point (it has strong covalent bond- doesnt conduct because electrons are fixed)
• Graphite

  -in layers

  -only non-metal that conducts as it has a delocalised electron
• atoms-> made up of protons and neutrons in the nucleus and electrons orbiting the nucleus in its outer electron shells. basic building blocks
• mass number of protons= 1
• mass number of neutrons= 1
• mass number of electrons= 1/1837
• charge of protons= +1
• charge of neutrons= 0
• charge of electrons= -1
• -mass number?

  -atomic number?

  how many neutrons/protons and electrons in oxygen?

  -number of protons and neutrons

  -number of protons (also electrons)

  -8 neutrons

  -8 protons

  -8 electrons

  
• relative atomic mass=

  
• Bonding:

  1. Ionic-> between metals and non-metals
  2. Covalent-> between two or more non-metals
  3. Metallic-> between metals
• Dalton model of an atom

  1. Atoms are small particles that cannot be created, divided, or destroyed

  2. Atoms of the same element are exactly alike, and atoms of different elements are different

  3. Atoms join with other atoms to make new substances
• J.J. Thomson's discovery

  • Atoms can be divided into smaller parts
  • Particles have a negative charge
• Thomson's "plum-pudding" model


  Negative electrons are scattered throughout soft blobs of positively charged material
• Rutherford's experiment

  1. Shot a beam of positively charged particles into a sheet of gold foil

  2. Most particles continued in a straight line

  3. Some particles were deflected to the sides

  4. A few bounced straight back
• Rutherford's model


  • Most of the atom's mass is found in a region in the center called the nucleus
  • The atom is mostly empty space, and the electrons travel in random paths around the nucleus
• Structure of an atom

  • Nucleus containing protons and neutrons
  • Surrounded by electrons in shells
• Atoms


  Neutral, with protons having +1 charge and electrons having -1 charge
• Amount of protons = amount of electrons, so that the charges cancel
• Nucleus of an atom

  • Very small compared to the overall size of the atom
• Most of the mass of an atom is concentrated in the nucleus
• Mass (nucleon) number


  Number of protons + neutrons
• Atoms of a given element

  • Have the same number of protons in the nucleus, which is unique to that element
• Isotopes


  Different atoms of the same element containing the same number of protons but different numbers of neutrons in their nuclei
• Calculating the numbers of protons, neutrons and electrons in atoms

  1. Atomic (proton) Number = number of protons (= number of electrons if it's an atom, because atoms are neutral)

  2. Number of neutrons = Mass number - Atomic number
• Isotopes


  Atoms of the same element with the same number of protons but different numbers of neutrons
• Existence of isotopes

  Relative atomic masses of some elements not being whole numbers