Module 2 - Atoms and the Periodic Table

• John Dobereiner's triad grouped elements which exhibit very similar characteristics in threes or triads. (Li, Na, K)
• Newlands' Law of Octaves - When elements are arranged in order of increasing atomic masses, the properties of the 8th element are a repetition of properties of the 1st element (H, F).
• Mendeleev’s Table (1869) the atomic weights of the elements were related to the periodic variation in their properties. (period is row and group is column)
• Henry Moseley (1894) suggested that it was the charge of the nucleus and not the atomic weight that accounted for the periodic trends in the properties of the elements. The modern periodic law is stated as ‘properties of elements are a function of their atomic number.’
• Metals - solids at room temperature (except for Hg, which is liquid), shiny, conduct electricity, and are ductile and malleable. Form alloys (solutions of one metal dissolved in another); brass, for example, is an alloy of copper and zinc. In chemical reactions, they tend to give up electrons.
• Nonmetals - Except for hydrogen (H), they lie on the right side of the Periodic Table. Do not conduct electricity. In chemical reactions, they tend to accept electrons.
• Metalloids - Both possess properties of metals and nonmetals Semiconductors for computer chip industries.
• The size (radius) of an atom is determined by the distance from the nucleus to the outermost occupied electron shell. Increases from TOP to BOTTOM and RIGHT to LEFT.
• Similar charges repel (electrons + electrons).
• Ionic Radius - size of an ion kapag nababawasan o nadadagdagan. ex. flourine accepts electrons, mas lalaki. sodium repels electrons, mas liliit at ma overpower ng proton.
• Electron Affinity - amount of energy RELEASED when atom gains an electron in a gaseous state.
• Flourine has the highest electron affinity. Metals have the lowest.
• Ionization Energy - amount of eery needed to REMOVE an electron in a gaseous state.
• Ionization energy increases from bottom to top and left to right.
• Electronegativity - the tendency to attract electrons to itself or the greediness and generosity of electrons. last column not included because they are already full of electrons.
• C and O - O is more electronegative.