A Covalent Chemical Bond is One in Which _____

Introduction

Merely when two atoms of the same element form a covalent bond are the shared electrons actually shared equally between the atoms. When atoms of different elements share electrons through covalent bonding, the electron will be drawn more than toward the cantlet with the higher electronegativity resulting in a polar covalent bail. When compared to ionic compounds, covalent compounds usually take a lower melting and boiling bespeak, and accept less of a tendency to dissolve in water. Covalent compounds tin be in a gas, liquid, or solid land and exercise not comport electricity or heat well. The types of covalent bonds tin can be distinguished past looking at the Lewis dot structure of the molecule. For each molecule, at that place are different names for pairs of electrons, depending if it is shared or not. A pair of electrons that is shared between two atoms is called a


bond pair

. A pair of electrons that is

not

shared between 2 atoms is called a


alone pair

.

Octet Rule

The


Octet Rule


requires all atoms in a molecule to take 8 valence electrons–either by sharing, losing or gaining electrons–to become stable. For Covalent bonds, atoms tend to share their electrons with each other to satisfy the Octet Rule. It requires eight electrons because that is the amount of electrons needed to fill a
s– and
p– orbital (electron configuration); also known as a noble gas configuration. Each atom wants to become equally stable as the noble gases that have their outer valence vanquish filled because noble gases have a accuse of 0. Although it is important to call up the “magic number”, 8, annotation that in that location are many Octet rule exceptions.

Example: Equally you lot tin run into from the moving picture below, Phosphorus has only 5 electrons in its outer trounce (bolded in red). Argon has a full of eight electrons (bolded in ruby), which satisfies the Octet Dominion. Phosphorus needs to gain 3 electrons to fulfill the Octet Rule. Information technology wants to be like Argon who has a full outer valence vanquish.

More than examples can be found here.

Single Bonds

A


single bond

is when ii electrons–one pair of electrons–are shared between two atoms. It is depicted by a single line betwixt the ii atoms. Although this course of bond is weaker and has a smaller density than a double bail and a triple bond, information technology is the virtually stable because it has a lower level of reactivity meaning less vulnerability in losing electrons to atoms that desire to steal electrons.

Double Bonds

A

Double bond

is when ii atoms share 2 pairs of electrons with each other. It is depicted by two horizontal lines between two atoms in a molecule. This type of bond is much stronger than a single bond, merely less stable; this is due to its greater corporeality of reactivity compared to a unmarried bail.

Triple Bond

A


Triple bail

is when three pairs of electrons are shared between two atoms in a molecule. It is the least stable out of the 3 general types of covalent bonds. It is very vulnerable to electron thieves!

Polar Covalent Bond

A


Polar Covalent Bail


is created when the shared electrons between atoms are not equally shared. This occurs when one cantlet has a higher electronegativity than the atom it is sharing with. The atom with the higher electronegativity will have a stronger pull for electrons (Similiar to a Tug-O-War game, whoever is stronger commonly wins). As a result, the shared electrons will be closer to the atom with the higher electronegativity, making information technology unequally shared. A polar covalent bail will outcome in the molecule having a slightly positive side (the side containing the atom with a lower electronegativity) and a slightly negative side (containing the atom with the higher electronegativity) considering the shared electrons will be displaced toward the atom with the higher electronegativity. As a consequence of polar covalent bonds, the covalent compound that forms will take an electrostatic potential. This potential will brand the resulting molecule slightly polar, assuasive information technology to form weak bonds with other polar molecules. One example of molecules forming weak bonds with each other as a result of an unbalanced electrostatic potential is hydrogen bonding, where a hydrogen atom will interact with an electronegative hydrogen, fluorine, or oxygen atom from another molecule or chemical grouping.

Example: Water, Sulfide, Ozone, etc.

Every bit you can see from the picture above, Oxygen is the large buff creature with the tattoo of “O” on its arm. The little bunny represents a Hydrogen cantlet. The blue and red bow tied in the centre of the rope, pulled by the two creatures represents–the shared pair of electrons–a unmarried bond. Because the Hydrogen atom is weaker, the shared pair of electrons will be pulled closer to the Oxygen atom.

Nonpolar Covalent Bond

A


Nonpolar Covalent Bail


is created when atoms share their electrons equally. This normally occurs when two atoms have like or the same electron analogousness. The closer the values of their electron analogousness, the stronger the attraction. This occurs in gas molecules; also known equally diatomic elements. Nonpolar covalent bonds have a similar concept as polar covalent bonds; the atom with the higher electronegativity will depict away the electron from the weaker ane. Since this statement is true–if we use this to our diatomic molecules–all the atoms will have the aforementioned electronegativity since they are the aforementioned kind of chemical element; thus, the electronegativities volition abolish each other out and will have a charge of 0 (i.e., a nonpolar covalent bond).

Examples of gas molecules that have a nonpolar covalent bond: Hydrogen gas atom, Nitrogen gas atoms, etc.

As you tin run across from the picture show higher up, Hydrogen gas has a full of 2 Hydrogen atoms. Each Hydrogen atom has 1 valence electron. Since Hydrogen can only fit a max of 2 valence electrons in its orbital, each Hydrogen atom just needs one electron. Each atom has 1 valence electron, so they tin can just share, giving each atom two electrons each.

References

1. Petrucci, Ralph H., Harwood, William South., Herring, F. G., and Madura Jeffrey D. “General Chemistry: Principles & Mod Applications.” 9th Ed. New Jersey: Pearson Education, Inc., 2007. Impress.
2. Vaczek, Louis. “The Enjoyment of Chemical science.” New York: Viking Press, 1968.
3. Pickering, H. S. “The Covalent Bond.” London: Wykeham Publications Ltd., 1977.
4. Kotz, Treichel, Townsend. “Chemistry and Chemical Reactivity: OWL Eastward-Book Edition.” seventh Ed. Ohio: Cengage Learning, 2008.
5. Lagowski, J. J. “The Chemical Bail.” Boston: Houghton Mifflin Company, 1966.
6. Bacskay, George Grand.; Reimers, Jeffrey R.; Nordholm, Sture.
   “The Mechanism of Covalent Bonding.”
   J. Chem. Educ.
   1997
   74
   1494.
7. Reimers, Jeffrey R.; Bacskay, George Grand.; Nordholm, Sture. “The Nuts of Covalent Bonding.”
   J. Chem. Educ.
   1997
   74
   1503.

Problems

1. Make up one’s mind the type(s) of bond(s) in

• Benzene (C_{half dozen}H_vi)
• NO
  3
  
  (Nitrate)
• F₂(Fluorine gas)

Solution:

two. Write the electron configuration and decide how many electrons are needed to achieve the nearest noble-gas configuration for the following:

• Arsenic (As)
• Silicon (Si)
• Tellurium (Te)

Solution:

3. Make up one’s mind which molecules are polar and which molecules are nonpolar for the following:

• Oxygen gas (O₂
  )
• Hydrochloric acid (HCl)
• Carbon dioxide (CO₂₎

Solution:

4. Which of the following statements are true? (There tin can exist more than i true statement.)

1. A covalent bail is the same every bit a ionic bond.
2. The Octet rule just applys to molecules with covalent bonds.
3. A molecule is polar if the shared electrons are every bit shared.
4. A molecule is nonpolar if the shared electrons are are equally shared.
5. Marsh gas gas (CH₄
   ) has a nonpolar covalent bond because information technology is a gas.

Solution: Only d) is truthful.

5. Match each cantlet or molecule with its corresponding letter(s):

• Nitrogen gas
• Argon
• Carbon monoxide
• Hydrogen gas

a) Nonpolar covalent bail

b) Polar covalent bond

c) Follows the Octet Rule

d) Noble gas

e) Ii lone pairs

f) Unmarried bail

Solution:

• Nitrogen gas: a), c), eastward)
• Argon: c), d)
• Carbon monoxide: b), c), e)
• Hydrogen gas: c), f)

Contributors and Attributions

• Camy Fung (UCD), Nima Mirzaee (UCD)