covalent bonding

why covalent bonds form

Covalent bonds form because they give atoms a more stable arrangement of electrons. Look at the oxygen atoms in the Figure 1.2. Alone, each oxygen atom has six valence electrons. By sharing two pairs of valence electrons, each oxygen atom has a total of eight valence electrons. This fills its outer energy level, giving it the most stable arrangement of electrons. The shared electrons are attracted to both oxygen nuclei, and this force of attraction holds the two atoms together in the oxygen molecule.

covalent compounds and diatomic elements

The two atoms that are held together by a covalent bond may be atoms of the same element or different elements. When atoms of different elements form covalent bonds, a new substance, called a covalent compound, results. Water is an example of a covalent compound. A water molecule is modeled in the Figure 1.1. A molecule is the smallest particle of a covalent compound that still has the properties of the compound. Q: How many valence electrons does the oxygen atom (O) share with each hydrogen atom (H)? How many covalent bonds hold the water molecule together? A: The oxygen atom shares one pair of valence electrons with each hydrogen atom. Each pair of shared electrons represents one covalent bond, so two covalent bonds hold the water molecule together. The diagram in the Figure 1.2 shows an example of covalent bonds between two atoms of the same element, in this case two atoms of oxygen. The diagram represents an oxygen molecule, so its not a new compound. Oxygen normally occurs in diatomic (two-atom) molecules. Several other elements also occur as diatomic molecules: hydrogen, nitrogen, and all but one of the halogens (fluorine, chlorine, bromine, and iodine). Q: How many electrons do these two oxygen atoms share? How many covalent bonds hold the oxygen molecule together? A: The two oxygen atoms share two pairs of electrons, so two covalent bonds hold the oxygen molecule together.



sharing electrons

A covalent bond is the force of attraction that holds together two atoms that share a pair of valence electrons. The shared electrons are attracted to the nuclei of both atoms. This forms a molecule consisting of two or more atoms. Covalent bonds form only between atoms of nonmetals.

instructional diagrams

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in covalent bonds, the atoms that form bonds

a) may be metals or nonmetals.

b) transfer electrons.

-->  c) may both be the same element.

d) all of the above

electrons in covalent bonds are attracted to the nucleus of just one atom.

a. true

-->  b. false

a covalent bond always includes a pair of electrons.

-->  a. true

b. false

elements that form diatomic molecules include

a) oxygen.

b) hydrogen.

c) chlorine.

-->  d) all of the above

the formation of one or more covalent bonds always results in a covalent compound.

a. true

-->  b. false

which of the following is a covalent compound?

-->  a) h2o

b) nacl

c) o2

d) two of the above

diagram questions

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