Name: electronegativity and covalent bond polarity
Uploaded: 2026-06-01T06:27:57.594Z
Duration: 1 min 29 s
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Covalent Bonds

Covalent bonds share valence electrons, which fill each atom&#x2019;s outer shell and create one stable molecule; in this case, with a single bond.The number of covalent bonds can increase depending on how many electrons are shared. For example, when two oxygen atoms, each with six valence electrons, share two pairs of electrons, a double bond forms.These bonds are nonpolar covalent because the electrons are shared evenly between the atoms. The atoms have the same attraction for the electrons in the covalent bond, meaning they have the same electronegativity.If two different elements have similar electronegativity, such as carbon and hydrogen, they share electrons relatively equally, forming a nonpolar covalent bonds.The more strongly an atom attracts the electrons in a covalent bond, the more electronegative the atom.When two different elements with very different electronegativity bond together, they share electrons unequally, forming a polar covalent bond.For example, water has one oxygen atom and two hydrogen atoms. The oxygen atom holds the negatively charged electrons most of the time, giving it a partial negative charge.This situation leaves the hydrogen atoms with a partial positive charge, which makes the compound polar.These covalent bonds usually form between nonmetals such as carbon, hydrogen, nitrogen, oxygen, and chlorine.

covalent bonds

When two atoms share electrons to complete their valence shells they create a covalent bond. An atom&#x2019;s electronegativity&#x2014;the force with which shared electrons are pulled towards an atom&#x2014;determines how the electrons are shared. Molecules formed with covalent bonds can be either polar or nonpolar. Atoms with similar electronegativities form nonpolar covalent bonds; the electrons are shared equally. Atoms with different electronegativities share electrons unequally, creating polar bonds.<h4>A Covalent Bond Is Formed by Two Shared Electrons</h4>The number of covalent bonds that an atom can form is dictated by how many valence electrons it has. Oxygen, for example, has six out of eight possible valence electrons, meaning that each oxygen atom needs two more electrons to become stable. Oxygen can form single bonds with two other atoms, as it does when it forms water with two hydrogen atoms (chemical formula H2O). Oxygen can also form a double bond with just one other atom that also needs two more electrons to complete its octet (e.g., another oxygen atom). Carbon has four valence electrons and therefore can form four covalent bonds, as it does in methane (CH4).When a covalent bond is made, both atoms share a pair of electrons in a hybrid orbital that differs in shape from a normal orbital. The electrons participating in the bond thus orbit in a modified path around the nuclei of both atoms. Covalent bonds are strong and, once formed, cannot be broken by physical forces.<h4>Electronegativity Determines Whether a Molecule Is Polar or Nonpolar</h4>Electronegativity is the tendency of an atom to attract electrons in a bond. The most electronegative atom is fluorine. Starting with fluorine at the top right corner of the periodic table (omitting the noble gases in the rightmost column), the electronegativity of atoms tends to decrease with diagonal leftward movement down the periodic table, such that atoms with the lowest electronegativities are at the bottom left corner (e.g., francium, or Fr). If atoms have extremely different electronegativities, they will likely form ions instead of covalent bonds. However, for atoms that form covalent bonds with one another, their electronegativity values determine whether the bond will be polar or nonpolar.A nonpolar bond is one in which the electrons are shared equally, and there is no charge across the molecule. A polar bond, by contrast, occurs when one atom is more electronegative than another and pulls the electrons toward it. Polar bonds have a partial negative charge on one side and a partial positive charge on the other, which is important because it causes polar molecules to behave differently than nonpolar ones.Polar molecules are hydrophilic because their partial charges attract them to other charged molecules, which also means they are soluble in water. Nonpolar molecules&#x2014;those containing long stretches of hydrocarbons, such as fats&#x2014;are said to be hydrophobic. Unlike polar molecules, nonpolar molecules will not dissolve in water. Cells are often surrounded by fluid and have cytoplasms that contain water. Thus, the way a molecule interacts with water and other charged molecules impact how it is transported and used by cells.

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Learn by watching this video about Covalent Bonds and Electronegativity at JoVE.com

electronegativity and covalent bond polarity

Covalent bonds form when two atoms share electrons to fill their valence shells. The way those shared electrons are pulled depends on electronegativity, which is an atom’s ability to attract electrons in a bond. When atoms have similar electronegativities, they form nonpolar covalent bonds. When their electronegativities differ, the bond is polar because the electrons are shared unevenly.

The number of covalent bonds an atom can make depends on its valence electrons. Oxygen has six valence electrons, so it needs two more to reach a stable octet. It can make two single bonds, as in water with two hydrogen atoms, or one double bond with another oxygen atom. Carbon has four valence electrons and can form four covalent bonds, as it does in methane.

When a covalent bond forms, the two atoms share a pair of electrons in a hybrid orbital. This orbital has a different shape from a normal orbital, so the electrons move in a modified path around both nuclei. Covalent bonds are strong, and physical forces cannot break them once they are formed.

Electronegativity follows a pattern on the periodic table. Fluorine is the most electronegative atom. Moving diagonally down and left across the table, electronegativity tends to decrease, and the lowest values are near the bottom left, such as francium. If two atoms have very different electronegativities, they are more likely to form ions instead of a covalent bond.

Polar and nonpolar covalent bonds affect how molecules behave. A nonpolar bond shares electrons equally, so there is no charge across the molecule. A polar bond creates a partial negative side and a partial positive side. That difference matters because polar molecules are hydrophilic, which means they are attracted to water and are usually soluble in it.

Nonpolar molecules behave differently. Molecules with long hydrocarbon stretches, such as fats, are hydrophobic and do not dissolve in water. Cells are surrounded by fluid, and their cytoplasm contains water. Because of that, whether a molecule is polar or nonpolar affects how it moves through cells and how cells use it.

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Electronegativity and Covalent Bond Polarity

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