phys sci

• what is chemistry?


  a branch of natural science that deals principally with the properties of substances.
• what are the theories on atoms?

  matter is composed of the 4 elements. gold and silver are elements not made up of the main 4.
• the early theories on atoms.

  • elements are composed of indivisible atoms.
  • atoms of given element are identical.
  • atoms of diff element have diff masses.
  • compounds are formed by combo of atoms of diff elements.
• what was the first discovered particle?

  electron
• what is the JJ Thomson Cathode Ray Tube experiment?

  rays were produced in tube deflected by an electrical field and formed negatively charged particles called electrons.
• plum-pudding model

  
• what is ernest rutherford’s gold foil experiment?

  positively charged particles at a thin piece of gold foil. most passed through, few were deflected and some were greatly deflected and bounced back.

  
• ernest rutherford’s gold foil experiment

  
• the bohr model, a planetary model of an atom with center, nucleus, rings with orbiting electrons.

  
• what model is this?

  wave mechanical model. the atoms are dense and positively charged nucleus.

  
• name the atomic models.

  • solid sphere model (dalton)
  • plum pudding model (thomson)
  • planetary model (rutherford)
  • bohr model
  • quantum model (schrödinger)

  
• what is an element?


  substances that cannot be broken down or decomposed by chemical means.
• compounds are...

  composed of 2 or more elements chemically combined in definite proportions by mass.
• what is a mixture?

  combination of two or more pure substances that can be separated by physical means. compositions are not definite or fixed.
• electrons are particles of an atom that can be shared or gained by an atom.
• the more energy levels are...

  the further valance electrons are from the protons / neutrons in the center.
• the less valance...

  the more likely it is for electrons to transfer to another atom.
• atomic radius

  across the period : decreasing from left to right
• high atomic number =

  more protons, atomic radius is smaller
• what is electronegativity?

  atom's ability to attract and bind electrons to itself.
• electronegativity from left to right...

  elements with less number of valence electrons = less electronegativity