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PERIODICITY (Periodic Trends (Trends in properties of metals and non-metal…

- - - - The change in energy released which accompanies addition of an electron to an atom in gaseous state.
      - Negative sign meaning energy released (exothermic)
    - - Increases across a period from left to right
      - Decreases down a group from top to bottom
  - - - Relative attractions that an atom has for a shared pair of electrons in a covalent bond
    - - Electronegativity increases across period from left to right.This is because since electrons are pulled closer to nucleus (see atomic radius), more difficult to remove them.
      - Electronegativity decreases down a group from top to bottom. This is because atomic radii increase down group, making easier to remove electron. Also because of shielding effect weakens forces between nucleus and outer electrons.
  - - - The minimum energy required to remove 1 mol of electrons from 1 mol of neutral gaseous atoms in ground-state.
      - Positive sign meaning energy used (endothermic)
    - - IE increases across period from left to right.This is because since electrons are pulled closer to nucleus (see atomic radius), more difficult to remove them.
      - IE decreases down a group from top to bottom. This is because atomic radii increase down group, making easier to remove electron. Also because of shielding effect weakens forces between nucleus and outer electrons.
  - - - Distance from center to the outer most region in ion
    - - Radii of cations (e.g. Mg+) are smaller than their parent.This is because there are more protons than electrons in the cation, so valence are more strongly attracted to nucleus.
      - Radii of anions(e.g. Cl–) are larger than their parent.This is because the extra electron in the anion results in greater repulsion between valence electrons, thus larger radius.
      - Ionic radius increases as you move from top to bottom on the periodic table.This is because each row adds a new electron shell.
      - Ionic radius decreases as you move across the periodic table, from left to right.More protons are added, but the outer valence shell remains the same, so the positively charged nucleus draws in the electrons more tightly. But, for the nonmetallic elements, ionic radius increases because there are more electrons than protons.
  - - - These trends occur due to combination of trends above
    - - Metallic character decreases across period from left to right
      - Metallic character increases down a group from top to bottom
      - Tend to have low IE values – tend to lose electrons. Thus they are oxidized
  - - - Distance from center to the outer most region
    - - Atomic radius decreases across period from left to right. Nucleus’s positive charge is greater relative to charge of electrons in same shell, pulling electrons closer to nucleus and thus reducing atomic radius .
      - Atomic radius increase down group from top to bottom. Each new period begins with new energy level which is farther from nucleus, increasing atomic radius.