Bonds between atoms shape the molecules of the atmosphere, the ocean, and and everything between them. Covalent bonding is one of the mechanisms that holds atoms together in compounds. Water is held together by covalent bonds as are carbon dioxide and ammonia.
What is chemical bonding?
Chemical bonding joins atoms into molecules. Stable compounds form when a molecule has a lower energy state than the separate atoms had, that is, when it takes less energy for the atoms to stay together than to exist independently.
The two extreme types of bonds are the ion bond, in which one atom takes electrons from another, and the covalent bond, in which atoms share electrons. Intermediate types of bonds exist as well.
What is covalent bonding?
In covalent bonding, atoms share electrons. Electrons exist in shells around an atomic nucleus, the way the layers of an onion surround its center. Each shell has a certain natural number of electrons it tends to hold. If it has too many electrons, it wants to remove the excess. If it has too few, it wants more. Atoms form molecules by trying to obtain the right number of electrons in their shells. The noble gases seldom form molecules because their outer shells already have the exact number of electrons they need. In covalent bonds, separate atoms share electrons in a way that tends to complete their shells.
What is the difference between covalent bonding and ionic bonding?
In ion bonds, one atom takes electrons from another. The atom that had too many electrons is whittled down to a complete outer shell and the atom with an incomplete outer shell adds the electrons it needs.
The molecule holds together because the atom that took electrons now has a negative charge (because electrons are negative) and the atom that gave up electrons now has a positive charge (also because electrons are negative). The positive and negative ions (atoms with a charge) attract each other the way opposite poles of two magnets attract.
In covalent bonds, atoms do not give or take electrons. Instead, they share pairs of them. Atoms needing more electrons to fill their shells count the shared elections as part of their shell. In this way, all shells are filled. These molecules are held together by the way each nucleus is attracted to the electrons in its outer shell. Since the nuclei in effect share an outer shell, each is attracted to the outer shell of the other.
What is electronegativity?
Electronegativity is the tendency of an atom to attract bonding electrons. Electronegativity generally increases from left to right and from bottom to top in the periodic table. Metals are the least electronegative elements.
Elements with high electronegativity are very reactive, because they easily form bonds by taking electrons. Oxygen and fluorine are the two elements with the highest electronegativity and are very reactive.
Elements with very low electronegativity are also very reactive, because they give up their electrons easily. Caesium is the stable element with the lowest electronegativity, and it can explode on contact with water.
Chemical bonds are an important topic in chemistry since they are crucial to compounds, and compounds are an essential part of all life.