Because the atoms having covalent bonds "share" the involved electrons equally. This is one of the effects of Quantum Mechanics, the shape of the orbital probability cloud containing the electrons in these bonds changes shape to encompass both atoms valence bands.
formation of a covalent bond
A covalent bond is a form of chemical bonding that is characterized by the sharing of pairs ofelectrons between atoms, and other covalent bonds. In short, the stable balance of attractive and repulsive forces between atoms when they share electrons is known as covalent bonding.[1]Covalent bonding includes many kinds of interaction, including σ-bonding, π-bonding, metal to metal bonding, agostic interactions, and three-center two-electron bonds.[2][3] The term covalent bond dates from 1939.[4] The prefix co- means jointly, associated in action, partnered to a lesser degree,etc.; thus a "co-valent bond", essentially, means that the atoms share "valence", such as is discussed in valence bond theory. In the molecule H2, the hydrogen atoms share the two electrons via covalent bonding. Covalency is greatest between atoms of similar electronegativities. Thus, covalent bonding does not necessarily require the two atoms be of the same elements, only that they be of comparable electronegativity. Although covalent bonding entails sharing of electrons, it is not necessarily delocalized. Furthermore, in contrast to electrostatic interactions ("ionic bonds") the strength of covalent bond depends on the angular relation between atoms in polyatomic molecules.
The term 'covalent' is usually applied to a bond in the context of chemistry; electrons are the particles that participate in bonding. The act of bonding helps atoms achieve a stable configuration, one way of achieving this is by sharing its outer electrons in a bond. One might say the stability of an atom increases thereby.
When two atoms are bonded together but have an unequal sharing of electrons the newly formed molecule is said to be bound by ionic bonds. This unequal sharing is due to differential attractions of the atoms in the molecule to the electrons.
If the starting point are elements then the inner shell electrons (non valence) these orbit the nuclei of the atoms and the formation of a chemical bond does not affect these materially. What happens to the valence electrons depends on the bond formed. In an ionic bond electrons are transferred from say the metal atom to the nonmetal- these electrons essentially "orbit" the nuclei of the cations and anions. They are "localised". When a covalent bond is formed the valence electrons involved are shared between the atoms, they "orbit" both nuclei. When the bond is polar covalent they spend a little more time nearer the more electronegative element. When a "delocalised"covalent bond is formed as in bezene or graphite the electrons orbit a number of atomic nuclei. In a metallic bond the valence electrons are also delocalised (the sea of electrons model) across the metal lattice, but in transition metals there is additional bonding between electrons in d orbitals (the tight bound electrons) and these electrons are essentially localised.
Covalent bonding
Covalent bonding occurs between two atoms that are both non metals
Covalent bonding occurs between the carbon and chlorine atoms in a CCl4 molecule. This type of bonding involves the sharing of electrons between atoms to achieve a stable electron configuration.
Covalent bonding is formed when atoms share electrons. In this type of bonding, atoms share one or more pairs of electrons to achieve a more stable electron configuration.
There are two basic types of chemical bonding: Ionic bonding and Covalent bonding. Ionic bonding occurs between a metal and a non-metal (i.e. Na + Cl --> NaCl) Covalent bonding occurs between two non-metals (i.e. H2 + O2 --> 2H2O)
electrons are shared between one or more atoms
Covalent bonding occurs when electrons are shared between adjacent atoms. This type of bonding is characterized by the sharing of electron pairs between atoms to achieve a stable configuration. It is typically seen in nonmetals and results in the formation of molecules.
covalent
The compound likely has covalent bonding. In covalent bonding, nonmetallic atoms share electrons to achieve a full outer electron shell, forming a stable compound. This type of bonding typically occurs between atoms of similar electronegativity.
Covalent bonding. It can be two types - polar covalent or nonpolar covalent. In polar covalent bonding, atoms do not share electrons equally. In nonpolar covalent bonding, atoms share electrons equally.
In a nonpolar covalent bond, the shared electrons are shared congruently throughout the molecule. This occurs when two atoms have similar electronegativities and therefore share the electrons equally.
Covalent Bonding