Atoms Reviewer

• An atom is a basic building block of matter. All matter is made of atoms.
• Atoms are composed of protons, neutrons, and electrons.
• Atomic models:

  * Tentativeness

  (key tenet of science)

  *Development of new atomic models

  (changes in light of new evidence)
• 5 Important people in finding atoms: Democritus(400 BC), John Dalton(1803), Joseph John Thomas(1904), Ernest Rutherford(1911), Niels Bohr(1913).
• Democritus (400 BC)

  * tiny particles

  *solid, hard, uniform

  * incompressible, indestructible

  * Atoms = Atomos(greek) = indivisible
• John Dalton (1803)

  *Chemist & Physicist

  *Pioneered development of modern atomic theory.

  *solid and hard spheres
• Joseph John Thompson (1904)

  *British Physicist

  * Discovered Electrons

  *Cathode-ray tubes*(proposed particles are embedded in a positive atom.
• Ernest Rutherford (1911)

  *British Physicist

  *Father of nuclear Physics

  *discovered presence of a proton nucleus

  *Gold Foil Experiment
• Niels Bhor (1913)

  *Danish physicist

  *Modified the Nuclear Model

  *Electrons on the orbit (fixed energy levels)
• Bonus! James Chadwick:

  *Discovered neutrons in the nucleus

  *studied berillium
• Atomic Inventory:

  Atomic Number(z) = number of protons

  Mass Number(a) = number of protons + neutrons

  Ground state: number of electrons = protons
• Subatomic Particles

  Atoms = the smallest amount of matter, retains an identity as a chemical element.

  Atoms are made of 3 particles:

  Electrons

  Neutrons

  Protons
• Atoms, Ions, Isotopes:

  Atoms

  * P=E

  * Overall charge = 0 or natural

  Ion

  * Atom loses/gains electrons

  -If loses, its a positive charge (cation)

  -If gains, its a negative charge (anion)

  Isotopes

  *same element

  *different atomic mass

  -due to different number of neutrons