Essay on Organic Chemistry

748 Words 3 Pages
Trends in the Periodic table
March 24, 2013

Four trends that will be covered:
Atomic size
Ionization Energy
Electron Affinity

Each of these has a group trend and a period trend
A group trend refers to what is happening with the atom as you travel up or down a column of the periodic table.
A period trend refers to what is happening with the atom as you move left or right across a row of the periodic table

Atomic Size
When discussing an atom’s size, usually the size being referred to is the radius. An atom’s radius is measured from the centre of the atom’s nucleus to its outermost electron shell. Atoms that have more electrons (which will have more electron shells) will have a greater atomic size. An
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Electrons found in an electron shell further away from the nucleus experience less attractive force and therefore it takes less energy to remove an electron.

The period trend for ionization energy is that it increases as you move from the left to the right. Lithium has lower ionization energy than oxygen. This is because as you move further to the right side of the periodic table there is an increase in the attractive force exerted by the protons in the nucleus of the atom. Due to this strong attractive force, more energy is required to remove an electron form its shell.

Electronegativity and Electron affinity

The group and period trends for electronegativity and electron affinity are the same as each other. The only difference is the definitions of the two. Electronegativity is the tendency of an atom to attract an electron. Electron affinity is the energy change that accompanies the addition of an electron.

The group trend for both electronegativity and electron affinity is that they decrease as you move from the top of the periodic table to the bottom. This is because of increased shielding as you move down the periodic table. Oxygen has a greater electronegativity than sulfur. This is because of the increased shielding as you move down the periodic table. An electron ring that is further away from the nucleus will experience less attractive force; therefore it is less likely that an electron can be

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