30 May
30May

Periodic trends have patterns that exist in the periodic table to illustrate different aspects of elements, including the size and electronic characteristics of elements. Trends include:


ionization energy

  • The ionization energy of an element usually increases from left to right. This is due to the stability of the valence shell.

  • The ionization energy of the elements decreases from top to bottom. This is due to electronic shielding.


electronegativity

  • From left to right in the periodic table, the electronegativity increases. 

  • If the valence shell of an atom is less than half, the energy required to lose electrons is less than the energy required to obtain electrons; it is easier to pull the electron into the valence shell than to donate the electron.


atomic radius

  • The atomic radius decreases from left to right. This is due to the increase in the number of protons and electrons across a period. 

  • The role of protons is greater than electrons. As a result, electrons are pulled toward the nucleus, resulting in a smaller radius.

  • The atomic radius increases from top to bottom. This is caused by electronic shielding.


melting point

  • Metals have a high melting point.

  • Most nonmetals have low melting points.


chemical reactivity

  • Period - reactivity increases as you go from the left to the right across a period. 

  • Group - reactivity decreases as you go down the group.


ion charge

  • On the Periodic Table metals (found on the left of the table) will be positive. Non-metals (found on the right) will be negative. 

  • The alkali metals form +1 ions. Hydrogen can form either +1 or -1 ions. The alkaline earth metals form +2 ions. In group 15, Nitrogen and Phosphorus usually form -3 ions. The halogens always form -1 ions. The noble gases don’t easily form ions. And many of the transition metals form more than one type of ion. 


Conductivity

  • Period - Decreases from left to right

  • Group - Increases from top to bottom 

  • In order for this element to conduct electricity, it must contain freely moving electrons. Generally, metals are good electrical conductors, and nonmetals are bad electrical conductors.

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