The bond between two atoms that share electrons.
For example, the formation of the chlorine molecule, which exists as a diatomic molecule (Cl2). Their union as ionic bond is not possible, because a chlorine atom can not transfer an electron to another atom, chlorine also complete its octet, it would get the first six electrons in its valence shell.
To explain the link of this molecule and others in which atoms join the same or similar electronegativity. Lewis suggested that a chemical bond can be formed when two atoms share a pair of electrons, so that both atoms complete their octet in the valence shell.
2s22p6 3s2 3p2 17Cl 1s2 3p2 1s2 3p1 2s22p6
Cl2 3p2 3s2 3p2 1s2 3p2
17Cl 2s22p6 3s2 3p2 3p2 3p1
In this form of marriage, the two chlorine atoms have 8 electrons in its valence shell. This union is known as covalent bonding. This link is when the electronegativity of two atoms that bind the same or different (bends that electronegativity is the force with which an atom attracts the bonding electrons).
is necessary to consider that the more electronegative element is fluorine atom, with a value arbitrarily consider Lewis (4). When the electronegativity difference between atoms is too large the bonding electrons are transferred completely to the more electronegative atom, forming an ionic bond, and when this difference is small, it means that atoms have similar attractive force on the electrons, so that share, forming a covalent bond.
nonpolar covalent bond, polar and coordinated.
• nonpolar covalent. When the electronegativity difference is zero, the bond is covalent and the electron cloud of the link is evenly distributed around the two nuclei of atoms they join. When this happens, we say that it is a nonpolar covalent. Usually formed by two identical atoms, for example, hydrogen molecules (H2), chlorine (Cl2), fluorine (F2). Represent these samples using the Lewis structure and diagram area, the fluorine molecule. Lewis Diagram
:
covalent bond Cloud
electronic link
Nuclei
polar covalent
• The polar covalency occurs when the electronegativity difference is greater than zero but less than 1.7. analyze the formation of the molecule of hydrogen bromide, HBr. Electronegativades table (found in chemistry textbooks in the chapter on chemical bonding), we obtain the value of each atom and we can determine the difference in electronegativity. • Br ₌
2.8
-
H ₌ 2.1 0.7 Difference
electronegativity
The bromine atom more strongly attract the electron pair and the electron density is higher in this atom, as shown:
representation of the electron cloud of a polar molecule
From this analysis, We conclude that the polar covalence is that which occurs when two atoms are linked by covalent bond have a partial electrical charge separation (δ and δ ₊ ⁻) caused by the difference in electronegativities. Δ ₊ δ
⁻
H - Br
coordinate covalent bond Such
exists when one of the two atoms brings the pair of addresses. Given this name because there is coordination between the two atoms so that both can meet the octet rule.
This link occurs when an atom has a pair of free electrons (eg, nitrogen, oxygen and sulfur, among others) and shares with another atom that needs electrons to complete the pair with a layer of eight electrons valence.
An example of coordinate covalent bond is the formation of ammonium ion (NH4 ₊) from ammonia (NH3 ₊), which shares the nitrogen electron pair with a proton (H ₊), which requires the pair of electrons to stabilize. The diagram and explanation
present it the teacher in class.
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