Today, we learned all about bonding. Specifically, we learned about the relationship between bonds and electronegativity.
From previous studies, we know that there are three main types of bonds:
- Ionic bonds exist between metals and non-metals, and electrons are transferred.
- Covalent bonds exist between non-metals and non-metals, and electrons are shared.
- Metallic bonds exist between metals and metals. In this type of bond, pure metals are held together by electrostatic attraction.
Electronegativity is a measure of how much an atom wants to gain electrons in a bond.
Atoms with greater electronegativity have a greater attraction towards electrons.
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| This diagram illustrates the periodic trend for electronegativity. |
As we explained above, covalent bonds exist between non-metals and non-metals that share electrons. Within this category, there are two types of sub-bonds called polar covalent bonds and non-polar covalent bonds. Polar covalent bonds form from an uneven sharing of electrons. Non-polar covalent bonds form from an equal sharing of electrons. The type of bond that is formed can be predicted by looking at the difference in electronegativity between the elements involved in the bond.
- If electronegativity is greater than 1.7, it is an ionic bond. Electrons are considered to be transferred.
- If electronegativity is less than 1.7, it is a polar covalent bond. Electrons are shared, but not equally.
- If electronegativity is 0, it is a non-polar covalent bond. Electrons are equally shared.
Ex.) Predict the type of bond formed:
H – H = non-polar covalent bond
O – H = polar covalent bond
H – Cl = non-polar covalent bond
Basically, if the atoms are different, you know there will be an electronegative difference.
Ex.) Calculate the electronegative difference in the following compounds:
CO = 3.44 - 2.55 = 0.89
OH = 3.44 - 2.20 = 1.24
BaI = 2.66 - 0.89 = 1.77
O2 = 3.44 - 3.44 = 0
That’s all for this lesson! Here's the obligatory video:
Posted by Michael.
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