sci 3

• Atom


  Smallest unit of an element that retains its chemical properties
• J.J. Thomson


  • Discovered electron in 1897
  • Conducted Cathode Ray Experiment
  • Proposed "Plum Pudding" model in 1904
  • Discovered isotopes in 1913
• Plum Pudding Model


  • Electrons in a soup of positive charges
• Eugen Goldstein


  • Observed the proton in 1886
  • Conducted Canal Ray Experiment
  • Proposed "Raising Pudding" model
• Ernest Rutherford


  • Proposed Nucleus Theory in 1910
  • Conducted Alpha Particle Gold-foil Experiment
  • Coined the word "Proton"
• Nucleus


  Core of an atom, contains protons and neutrons
• Electrons


  Negatively charged particles orbiting the nucleus
• Neutrons


  Particles found inside the nucleus, have no charge
• Atomic Number (Z)


  Total number of protons in the atomic nucleus
• Mass Number (A)


  Sum of the number of protons and neutrons
• Isotopes


  Atoms of the same element with different number of neutrons
• Notation of individual nuclides

  A pre-subscript equal to atomic number Z and a pre-superscript equal to the mass number A
• Notations of individual nuclides

  • Chlorine-35 (35Cl), Chlorine-37 (37Cl), Hydrogen-1 (1H), Hydrogen-2 (2H), Hydrogen-3 (3H)
• Scientist have always searched for patterns, regularities, and symmetries in nature
• If a pattern can be discovered, information and data can be arranged and organized in ways that will make it more understandable, meaningful, and useful
• An excellent example of this is the periodic table
• In grade 7, you learned about the periodic table
• The elements, the building blocks of matter, are listed in that table
• In your past lessons, you learned that atoms make up these elements are identified by their atomic number
• In this learning plan, you will learn that elements were arranged in the periodic table in rows and columns according to increasing atomic numbers
• This arrangement was based on properties of elements which were found to be repeated regularly through the elements arrange according to increasing atomic number
• The properties were recurring periodically, hence, patterns in the properties are observed
• You will recognize this incredible feature of the periodic table in this module, as you explore its full potential as a source of information about the elements
• It would be helpful to keep it handy all the time
• Learning objectives


  • State the contribution of scientists in the development of the Periodic table of elements
  • Recognize the names and symbols of the elements
  • Describe how elements are arranged in groups and periods using their electron configurations
  • Compare the physical and chemical properties of the elements within a group and across a period
  • Analyze the relationship between atomic orbitals and periodic trends of the elements
  • Classify the different chemical behaviors of the elements based on their periodic trends
• Periodic table


  A chart of the elements arranged into rows and columns according to their physical and chemical properties
• The work of scientists since ancient times to the present led to the development of our modern periodic table of elements
• Law of triads


  Dobereiner's observation that the atomic weight of strontium seemed to be halfway of calcium and barium
• Law of Octaves


  Newlands' observation that a regular interval within the arrangement occurs as the properties of the elements repeat every after the eighth element
• Newlands' arrangement was ridiculed because it seemed very simple; thus, his position was rejected
• Mendeleev's work


  • Studied the physical properties such as density, color, melting point, and atomic mass of each element
  • Noted chemical properties such as how each element reacted with other elements
  • Arranged the elements in a list using their atomic masses
  • Noticed that the properties of the elements seemed to repeat in a pattern
  • Arranged the elements in rows of increasing atomic mass
  • Grouped elements with similar properties in the same column
• Mendeleev predicted that scientists would discover elements that would fit into the spaces in his table
• Mendeleev's and Meyer's arrangements did not last long because more elements were discovered and the atomic masses of some elements were accurately measured, disagreeing with their arrangements
• Moseley's work


  • Discovered that atoms of an elements have a unique set of protons, which is different from those of other elements
  • Concluded that the atomic number of an element is equal to the number of protons
  • Proposed that it was more sensible to arrange the elements in the periodic table according to increasing atomic number rather than atomic mass
  • Showed how electrons are arranged in each type of an atom with the development of quantum mechanics
• The last revision of the periodic table came from Glenn Seaborg, who discovered plutonium in 1940 and most of the transuranic elements, leading to the repositioning of the actinide and lanthanide series
• Mendeleev placed tellurium before iodine despite the fact that tellurium has a greater atomic mass than iodine, because iodine's properties more closely resemble those of fluorine and chlorine
• Atomic number


  The number of protons in the nucleus of each of that element's atoms
• Moseley found that if elements were listed according to increasing atomic number instead of listing atomic mass, columns would contain elements with similar properties
• Element key


  Shows an element's chemical symbol, atomic mass, and a symbol that shows the state of matter at room temperature
• Grouping of elements


  • A families
  • B families
  • Representative elements (Groups 1A to 8A)
  • Noble gases or inert gases (Group 8A)
  • Transition elements (B families)
  • Lanthanide series
  • Actinide series