MATTER: COMPONENTS OF MATTER

• Atoms

  ● The smallest particle making up matter

  ● Greek word atomos = indivisible

  ● Made up of protons (+), electrons (-), neutrons (no charge)

  ● Inside the nucleus are protons and neutrons. Around the nucleus are electrons.

  ● Atomic number: number of protons
• Dalton’s Atomic Theory

  1. Each element is composed of indivisible particles called atoms.
  2. All atoms of a given element are identical to one another in mass and other properties.
  3. Atoms of one element cannot be changed into atoms of a different element; atoms are neither created nor destroyed
  4. Compounds are formed when atoms of more than one element combine; a given compound always has the same relative number and kind of atoms.
• Law of Conservation of Mass

  Mass is neither created nor destroyed in chemical reactions or physical transformations.
• Law of Definite Composition

  • Elemental composition of a pure compound is always the same everywhere.
  • e.g. carbon monoxide CO, where the mass ratio of C:O is always 1:1. For every 12 grams of carbon in carbon monoxide, there are always 16 grams of oxygen.
• Law of Multiple Proportions

  • When elements combine to form multiple compounds, they always do so in small, integer ratios.
  • e.g. NO2 , N2O5, Never NO1.5
• History of Atomic Theory

  A) Solid Sphere Model

  B) Dalton 1803

  C) Plum Pudding Model

  D) Thomson 1897

  E) Nuclear Model

  F) Rutherford 1911

  G) Planetary Model

  H) Bohr 1913

  I) Quantum Model

  J) Schrodinger 1926

  
• Solid Sphere Model

  • John Dalton 1803
  • Many wide-ranging experiments
  • Existence of the Atom
• Plum Pudding Model

  • J.J. Thomson 1897
  • Cathode Ray Tube Experiment
  • Existence of electrons
  • electrons are surrounded by a volume of positive charge like negatively charged "plums" embedded in a positively charged pudding
• Oil-drop experiment

  • Robert Milikan
  • charge of an electron (e)
• Existence of Radiactivity

  • Henri Becquerel
  • use of uranium compounds and fluorescent materials
  • existence of radioactivity
• Theory of Radioactivity

  • Pierre and Marie Curie
  • Many wide-ranging experiments on radioactivity
  • developed this theory
  • Marie Curie discovered the radioactive elements radium and polonium
• Nuclear Model

  • Ernest Rutherford 1911
  • Gold Foil Experiment
  • proposed the nuclear model of the atom
  • the atom is mostly empty space, with a dense "positively"-charged nucleus at the center
• Existence of Neutrons

  • James Chadwick
  • Bombardment of Beryllium with alpha particles experiment
• Bohr Model

  • Niels Bohr 1913
  • Many wide-ranging experiments on quantized energy of electrons
  • "negatively"-charged electrons revolve around the "positively"-charged nucleus in defined circular orbits
• Atomic number

  • total number of protons in the nucleus
  • provides information on the IDENTITY of the element
• Mass Number

  • sum of number of neutrons AND protons in the nucleus
  • provides information on the ISOTOPIC nature of a particular element
• What do you mean by isotopic nature?

  • existence of two or more isotopes of an element
• Isotopes

  • versions of the same element that have the same number of protons and different numbers of neutrons
• LABEL THE PARTS OF THE ELEMENT IN THE PERIODIC TABLE

  A) Mass nummber

  B) Atomic Number

  C) Symbol

  
• Atomic Mass

  • mass of nucleus
  • an electron is much lighter than a proton
• Average atomic mass = (mass of isotope 1 * abundance of isotope 1)+...
• Wave Nature of Light

  • Light can behave as a wave
  • As it does, we can measure wavelength
  • The electromagnetic spectrum lays out the associated frequencies of its various wavelengths
• ELECTROMAGNETIC SPECTRUM

  A) Radio

  B) Microwave

  C) Infrared

  D) Visible

  E) Ultraviolet

  F) X-ray

  G) Gamma Ray

  
• Electromagnetic Spectrum

  • The longer the wavelength the lower the frequency.
  • The longer the wavelength the higher the temperature
• WAVE PROPERTIES

  • Wavelength - distance from crest to crest
  • Speed of light - 300 km/sec - rate of motion of crests or troughs
  • Period - time between passage of successive crests
  • Frequency - number of crest passages per unit time
  • Amplitude - distance from level of crest or level of trough
• LABEL THE PROPERTIES OF WAVES

  A) Amplitude

  B) Amplitude

  C) Speed of Light

  D) Wavelength

  E) Frequency

  
• Blackbody Radiation

  • emission of light from hot objects
• Photoelectric Effect

  • emission of electrons from metal surfaces upon illumination
• Emission Spectra

  • emission of light from electronically excited gas atoms