Trends on the Periodic Table

Electronegativity

• Electronegativity- the measure of attraction an atom has for bonding electrons
• The higher the electronegativity, the more an atom wants to bond with another to complete their valence shell
• Electronegativity increases from left to right across a period and up a group
• It behaves this way because as you move more right and up, the halogens are the most reactive and REALLY want an electron to complete their valence shell
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Ionization Energy

• Ionization Energy- the amount of energy required to remove an electron from a gaseous atom
• Conceptually, this is the opposite of electron affinity
• First Ionization Energy- the energy required to remove the first electron
• First Ionization energy increases from left to right across a period due to increasing nuclear charge
• First Ionization energy decreases from top to bottom down a group
• Noble gasses have very high first ionization energy due to full valence shells
• It requires so much energy to pull away an electron from the top right elements because in the noble gases, they have a complete valence shell already, and the halogens are close, so they want to collect another electron rather than losing 7
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Electron Affinity

• Electron Affinity- the ability of an atom to accept an electron; energy is released when an electron is added
• First Electron Affinity- the energy change that occurs when an electron is added to a gaseous atom
• The amount of energy released increases left to right across a period
• The amount of energy released increases up a group
• It behaves this way because the halogens really want to gain an electron to complete the valence shell, while alkali metals want to lose one
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Atomic radius

• Atomic Radius- the 1/2 distance between the nuclei of two atoms of the same element
• Increases right to left across a period
• Increases down a group
• As the number of electron shells increase, so does the size of the atom. Incomplete valence shells are larger than complete ones due to repulsions
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Metallic Character

• Metallic Character- a set of physical and chemical properties including reactivity, conductance, ductility, and malleability
• Metallic character increases right to left across a period
• Metallic character increases down a group
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