Monday, May 2, 2011

Periodic Table Trends

There are many trends that can be identified on the periodic table of elements. The ones that we will be reviewing today include:

  • Metallic Properties
  • Atomic Radius
  • Ionization Energy
  • Electronegativity
  • Reactivity
  • Ion Charge
  • Melting/Boiling Point
  • Density

Density: Elements become more dense as we reach the middle of the periodic table.

Metallic Properties: Elements go from metallic -> non-metallic as we go from left to right on the periodic table. Elements at the bottom of a group are more metallic than those at the top of the group. 

Melting/Boiling Point: Elements at towards the centre of the table have the highest boiling points. Noble gases have the lowest melting point. 

Ionization Energy: This is the energy required to remove one electron from a neutral atom. This trend increases upwards towards to right of the periodic table. Meaning that helium has the highest ionization (holding tightly onto its electrons because it has a perfect full shell) energy, and francium has the lowest (eager to get rid of its one valence electron). Ionization energy is given in kj/mol.  

Electronegativity: This is basically a way of saying how much an atom wants to gain electrons. Noble gases are excluded from this trend because they already have a full valence shell, and therefore do not need to gain or lose any electrons. 

The trend of electronegativity is basically the same as ionization energy. So it goes up and to the right. Fluorine is the most electronegative element. 

High electronegativity: This atom strongly attracts neighbouring electrons, and may quite possibly even remove it. At the same time this atom holds tightly onto its own electrons. 

Low electronegativity: This element doesn't attract neighbouring electrons very well, in fact, it even allows its own electrons to be easily removed. 

Atomic Radius: The atomic radius decreases as we move towards to right side of the periodic table. Reason being that there are more protons and electrons, causing more attraction, which packs the atom together more tightly. The atomic radius increases down a group, because as you go downwards, the elements atoms have more shells which make the atom larger. 

Reactivity: Atoms that are closer to getting a full valence shell (by either gaining or losing electrons) tend to be more reactive. Noble gases are very stable because they already have a full shell. 

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