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Animation: Nonpolar and Polar Molecules

by Pearson
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Electronegativity is the tendency for an atom to pull electrons toward itself. Two atoms of the same element have equal electronegativities; in a covalent bond, they share electrons equally, forming a nonpolar covalent bond. The bond between the atoms in a molecule of hydrogen gas is a nonpolar covalent bond. Carbon and hydrogen have similar electronegativities. In methane, they share their electrons more or less equally. The carbon-hydrogen covalent bond is also relatively nonpolar. Atoms in a molecule do not always share electrons equally. Oxygen is much more electronegative than hydrogen, which means it attracts electrons more strongly. The oxygen atom in a water molecule hogs the electrons. Because of this unequal sharing of electrons, the oxygen atom in a water molecule actually has two regions of partial negative charge, and each hydrogen atom has a slight positive charge, even though the water molecule as a whole is neutral. Because of the unequal sharing of electrons and the resulting positive and negative poles, the bonds between oxygen and hydrogen are called polar covalent bonds, and a water molecule is said to be polar.
Electronegativity is the tendency for an atom to pull electrons toward itself. Two atoms of the same element have equal electronegativities; in a covalent bond, they share electrons equally, forming a nonpolar covalent bond. The bond between the atoms in a molecule of hydrogen gas is a nonpolar covalent bond. Carbon and hydrogen have similar electronegativities. In methane, they share their electrons more or less equally. The carbon-hydrogen covalent bond is also relatively nonpolar. Atoms in a molecule do not always share electrons equally. Oxygen is much more electronegative than hydrogen, which means it attracts electrons more strongly. The oxygen atom in a water molecule hogs the electrons. Because of this unequal sharing of electrons, the oxygen atom in a water molecule actually has two regions of partial negative charge, and each hydrogen atom has a slight positive charge, even though the water molecule as a whole is neutral. Because of the unequal sharing of electrons and the resulting positive and negative poles, the bonds between oxygen and hydrogen are called polar covalent bonds, and a water molecule is said to be polar.