Polar Bonds and Molecular Shape

A polar molecule is a molecule that has a net dipole moment due to its having unsymmetrical polar bonds. There are two factors that go into determining if a molecule is polar or not. To determine if a molecule (or ion) is polar or non-polar, you must determine both factors.

• The polarity of the individual bonds in the molecule.
• The shape or geometry of the molecule.

First, to determine if a given individual bond is polar, you need to know the electronegativity of the two atoms involved in that bond. To find the electronegativities of all the elements, look at the periodic table (follow the link below this answer under Web Links).

If the electronegativity of the two atoms has a difference of 0.3 or less, then the bond is non-polar. If the electronegativity difference is greater that 0.3 but less than 1.7, then the bond is polar. If the two values have a difference greater than 1.7, then the bond is ionic, which is just very very polar.

Once you know which bonds in the molecule are polar and which are non-polar, you must use the shape of the molecule. You need the shape because two polar bonds, if oriented correctly can cancel each other out (like two equally strong people pulling in opposite directions on a rope -- nobody moves).

The three possible outcomes:

• If all bonds are non-polar, then the whole molecule is non-polar regardless of its shape.
• If there is symmetry in the molecule so that the polarity of the bonds cancels out, then the molecule is non-polar. A common example of this is carbon dioxide, or CO2. The molecule is linear, and its Lewis dot structure is like this: O=C=O (this doesn't include two sets of lone pairs on each oxygen). The carbon-oxygen bond is a polar bond, but because they are exactly opposed to each other, the molecule is overall non-polar. Another example of this is CCl4, where each carbon-chlorine bond is polar, but the molecule is non-polar. Here, how they cancel out isn't as obvious, but they do. CCl4 is a tetrahedral molecule, and the 4 C-Cl polar bonds cancel each other out.
• If there are polar bonds but there is no symmetry such that they cancel each other out, the overall molecule is polar. Water is a typical example of this. The two O-H bonds are oriented in a V-shape, and so the don't cancel out. Similarly, CH3Cl is also polar. It is the same shape as CCl4 (see above), but now it doesn't have the same symmetry because there is only one C-Cl bond and the bonds don't cancel out anymore.

Given below is the difference in electronegativity of any two elements:

• 0.0-0.4 = nonpolar covalent bond
• 0.4-1.7 = polar covalent bond
• >1.7 = ionic bond
• For ex. Sodium and Chlorine (Na and Cl)
• Sodium's electronegativity = 0.93
• Chlorine's electronegativity = 3.16
• So, 3.16-0.93 = 2.23 which means NaCl bond is an ionic bond

Covalent bonds can either be polar or non-polar. You could determine this with the known electronegativities of the elements. First you have to represent the molecule by any means necessary (Lewis Dot Structure, lines, etc). This isn't nesessary for a compound with two atoms. Once drawn, you will know which atoms are bonded to the other atoms in the molecule. Then you look at the electronegativities for each element in one bond. If one atom's element has a higher electronegativity value than the other, then the bond is polar. If they are the same, then the bond is non-polar.

The reason a bond would be polar is because one atom has a higher electronegativity value, which means that the element has more attraction to electrons than the other. If it is attracting electrons more than the other, then the electrons are spending more time one one side. The disparity of electron distribution causes one side to be slightly negative (δ-) and the other to be slightly positive (δ+).

A covalent bond is a bond between two non-metallic elements. This means that they share electrons inside the molecules. OR A type of chemical bond in which there is mutual sharing of electrons between two atoms is called covalent bond. It is furthur classified into single, double, and triple covalent bond with respect to mutual sharing of one, two, and three bonds respectively. Their symbols are single, double, and triple lines between two atoms according to their type of covalent bond like one for single two for double and so on (e.g. Cl---Cl). The type of chemical bond in which one atom provides shared pair of electron for bond formation is called "Coordinate Covalent Bond". OR

Chemical bond formed between two atoms due to sharing of electron pair in which only one atom provides shared pair of electron for the formation of bond, is known as coordinate covalent bond or dative bond. In the formation of coordinate bond other atom does not provide electron for sharing. It is one sided sharing.

Formation of coordinate covalent bond is the property of atoms that have lone pair of electrons. The atom that provides electron pair is called "Donor". The other which takes it is called "Acceptor". Symbol:

Dative bond is represented by an arrow, pointing from donor atom to the acceptor.

For example 2 hydrogen atom 1s orbitals, each with 1 electron in, overlap to give a σ bonding orbital and a σ* antibonding orbital. The σ molecular orbital is as much lower in energy than the constituent atomic orbitals as the σ* orbital is higher in energy than them. however, both the electrons in the bond are in the σ bonding orbital, making them lower in energy, so bonding is favorable.

Non polar covalent bond is formed between 2 atoms of similar electronegativities and Polar covalent bond is formed between atoms of different electronegativities (electronegativity difference equal or less than 1.7). If a bond is too polarised (electronegativity difference more than 1.7) it is more favourable for electrons to fully transfer and ions are formed which attract electrostatically, with orbitals of the right shape and size to interact & ionic bond is formed.
is a form of chemical bonding that is characterized by the sharing of pairs of electrons between atoms, or between atoms and other ...