SCIENCE M.6 SEM1

• John Dalton (1766-1844

  English Chemist

  Theory of matter
• All elements are composed of atoms. It is impossible to divide or destroy an atom
• All atoms of the same elements are alike.
• Atoms of different elements are different.
• Atoms of different elements combine to form a compound. These atoms have to be in definite whole number ratios.
• What is the name of John Dalton's Theory?

  Matter
• What are elements made of?

  Atoms
• An atom of hydrogen and an atom of carbon are?

  different
• what compounds are made of?

  2 or more atoms of different elements
• ratio of atoms in HCI?

  1:1
• J.J THOMPSON (late 1800s)

  -English scientist

  -discovered electrons
• what did J.J Thomson discover?

  Electron
• what is the charge of an electron?

  negative charge
• what are cathode rays made of?

  negatively charged particles called electrons
• why do electrons move from the negative end of the tube to the positive end?

  repelled by negative charges and attracted to positive charge
• what was Thompson working with when he discovered the cathode rays?

  gas discharge tubes
• LORD ERNEST RUTHERFORD (1871-1937)


  -gold foil experiment
• what is the charge of an alpha particle?

  positive
• what is the charge of an beta particle?

  negative
• why is Ruherford's experiment called the gold foil experiment?

  because he used a thin sheet of gold foil
• how did he know that an atom was mostly empty space?


  when most of the particles passed through
• what happened to the alpha particles as they hit the gold foil?

  deflected / it pushes it away
• how did he know that the nucleus was positively charged?


  when some particles went straight back or were deflected
• NEILS BOHR (early 1900s)

  -danish physicist

  -proposed a model of atom that's similar to the solar system
• why would Bohr's model be called a planetary model of the atom?

  because electrons go around the nucleus like how planets orbit around the sun
• how do electrons in the same atom differ?

  each electrons has different amount of energy
• how many electrons can the 4th energy level bond?

  32 electrons
• how many electrons can the 1st energy level bond?

  2 electrons
• how many electrons can the 2nd energy level bond?

  8 electrons
• how many electrons can the 3rd energy level bond?

  18 electrons
• would an electron have to absorb or release energy to jump from the 2nd energy level to the 3rd energy level?

  it must absorb energy
• for an electron to fall from the 3rd energy level to the 2nd energy level, it must release energy.
• -       Luster – shiny

  -       Ductile – can be drawn into wire

  -       Malleable – can be hammered into sheets/flat

  -       High Melting Point – dense and solid except mercury

  -       Conductors – good conductors of electricity andand heat to flow

  -       Corrosion and Rust – reaction with water andand oxygen

  -       Sonorous – ringing soundand