chemistry

• Smallest particle that an element can be divided and still be that element.

  ATOM
• William crookes perfomed the cathode ray


  1832-1919
• It is a vaccum pump fitted with electrodes that is connected to an external source of electricity that produce a flash of light or ray.

  Cathode Ray
• In 1898, Joseph John Thompson found that atoms could sometimes eject a far smaller negative particles known as…..


  Electrons
• In 1904, What idea did Joseph John Thompson developed saying that the atom was made up of electrons scattered unevenly within an elastic sphere surrounded by a soup of positive charge to balance the electron’s charge. Like plums surrounded by pudding .


  Plum Pudding Model
• In what year was the magnitude of electron’s charge determed? and who determed it?

  1909, Robert Milikan
• In 1910, this student of J.J Thompson disagreed with the Plum Pudding Model. 


  Ernest Rutherford
• Ernest Rutherford devised an experiment to investigate the structure of positive and negative charges in the atom. What experiment did he performed?


  He fired helium nuclei at a piece pf gold foil. Only a few atoms thick. While most of them passes through. About 1 in 10,000 hit.
• Rutherford proposed are all concentrated on what?


  Nucleus
• What is a nucleus?

  A dense central core within the atom
• Rutherford called the charged particles in the nucleus as?

  protons
• In 1932, James Chadwick bombarded a thin sheet of beryllium with prticles, a very high energy radiation similar to rays was emitted by the metal. Later experiments showed that the tats actually consisted of electrically neutral partciles having a mass slighlty greater than that of protons. Chadwick called these parcticles as?


  neutrons
• What consist the atom?


  Proton-positively charged

  Neutron-neutral or no charge

  Electron-negatively charge
• Thompson discovered what?

  Rutherford discovered what?

  Chadwick discovered what?


  Electrons

  Neutrons

  Protons
• He studied under Rutherford at the Victoria University at Manchester. He refined Rutherford’s idea by saying that electrons were in orbits.


  Neils Bohr
• Rathet like planets orbiting the sun. Bohr said that each orbit can only able to contain a set number of?


  electrons
• Neils Henrik David Bohr proposed this new theory of the atomic structure to account for the fact that excited samples of the same element always emit the same set of wavelengths.


  The Bohr Atomic Theory
• Only…………., corresponding to certain definite energies are permitted for electrons in an atom.

  orbits of certain radii
• This is Bohr’s assumptions that says an electron in a permitted orbit has a specific energy and is in what stage?

  Allowed energy state
• An electron in an allowed energy state will ?


  Not radiate energy and therefore will not spiral into a nucleus
• Bohr’s assumptions that says electron is only emitted or absorbed by an electron as it changes from one allowed energy state to another. This energy is emitted or absorbed as a?


  photon, E=HV
• what is the plank’s constant in this formula E=HV?


  H
• Electrons normally exist in the lowest energy state called?

  Ground state
• When an electron jumps into higher

  energy state, it is said to be in an

  excited state
• It is achieved by supplying energy

  to the atom from external source.


  excitation
• The number of protons in the nucleus of each atom of an element.

  Atomic number
• Atomic number is the number of protons and also the number of?


  electrons
• Elements are put in what order in the

  atomic number on the periodic table?


  increasing
• It is the total number of neutrons and

  protons present in the nucleus of an atom of an element.

  Atomic Mass
• mass number=protons+neutrons or


  atomic number +neutrons

  electrons+neutrons
• The number of neutrons in an atom is

  equal to the difference between the

  mass number and the atomic number
• AEZ-

  A-stands for mass number

  E-element

  Z-?

  protons,atomic number or electron
• atoms of one element that have

  different mass numbers (different # of n)


  isotopes
• Protium, Deuterium, and Tritium are isotopes of?


  Hydrogen
• The chemical properties of an element are determined primarily by the (a) and (b) in its atoms; (c) do not take part in chemical changes under normal conditions. Therefore, isotopes of the same element have similar chemistries, forming the same types of compounds and similr reactivities.

  a-protons

  b-electrons

  c-neutrons