共价键

[ noun ]
a chemical bond that involves sharing a pair of electrons between atoms in a molecule
<noun.phenomenon>

Bond \Bond\ (b[o^]nd), n. [The same word as band. Cf. {Band},
{Bend}.]
1. That which binds, ties, fastens, or confines, or by which
anything is fastened or bound, as a cord, chain, etc.; a
band; a ligament; a shackle or a manacle.

Gnawing with my teeth my bonds in sunder,
I gained my freedom. --Shak.

2. pl. The state of being bound; imprisonment; captivity,
restraint. ``This man doeth nothing worthy of death or of
bonds.'' --Acts xxvi.

3. A binding force or influence; a cause of union; a uniting
tie; as, the bonds of fellowship.

A people with whom I have no tie but the common bond
of mankind. --Burke.

4. Moral or political duty or obligation.

I love your majesty
According to my bond, nor more nor less. --Shak.

5. (Law) A writing under seal, by which a person binds
himself, his heirs, executors, and administrators, to pay
a certain sum on or before a future day appointed. This is
a {single bond}. But usually a condition is added, that,
if the obligor shall do a certain act, appear at a certain
place, conform to certain rules, faithfully perform
certain duties, or pay a certain sum of money, on or
before a time specified, the obligation shall be void;
otherwise it shall remain in full force. If the condition
is not performed, the bond becomes forfeited, and the
obligor and his heirs are liable to the payment of the
whole sum. --Bouvier. --Wharton.

6. A financial instrument (of the nature of the ordinary
legal bond) made by a government or a corporation for
purpose of borrowing money; a written promise to pay a
specific sum of money on or before a specified day, given
in return for a sum of money; as, a government, city, or
railway bond.

7. The state of goods placed in a bonded warehouse till the
duties are paid; as, merchandise in bond.

8. (Arch.) The union or tie of the several stones or bricks
forming a wall. The bricks may be arranged for this
purpose in several different ways, as in {English bond} or
{block bond} (Fig. 1), where one course consists of bricks
with their ends toward the face of the wall, called
headers, and the next course of bricks with their lengths
parallel to the face of the wall, called stretchers;
Flemish bond (Fig.2), where each course consists of
headers and stretchers alternately, so laid as always to
break joints; Cross bond, which differs from the English
by the change of the second stretcher line so that its
joints come in the middle of the first, and the same
position of stretchers comes back every fifth line;
Combined cross and English bond, where the inner part of
the wall is laid in the one method, the outer in the
other.

9. (Chem.) A unit of chemical attraction between atoms; as,
oxygen has two bonds of affinity. Also called {chemical
bond}. It is often represented in graphic formul[ae] by a
short line or dash. See Diagram of {Benzene nucleus}, and
{Valence}. Several types of bond are distinguished by
chemists, as {double bond}, {triple bond}, {covalent
bond}, {hydrogen bond}.
[1913 Webster +PJC]

10. (Elec.) A heavy copper wire or rod connecting adjacent
rails of an electric railway track when used as a part of
the electric circuit.
[Webster 1913 Suppl.]

11. League; association; confederacy. [South Africa]
[Webster 1913 Suppl.]

The Africander Bond, a league or association
appealing to African, but practically to Boer,
patriotism. --James Bryce.
[Webster 1913 Suppl.]

{Arbitration bond}. See under {Arbitration}.

{Bond creditor} (Law), a creditor whose debt is secured by a
bond. --Blackstone.

{covalent bond}, an attractive force between two atoms of a
molecule generated by the merging of an electron orbital
of each atom into a combined orbital in the molecule. Such
bonds vary in strength, but in molecules of substances
typically encountered in human experience (as, water or
alcohol) they are sufficiently strong to persist and
maintain the identity and integrity of the molecule over
appreciable periods of time. Each such bond satisfies one
unit of {valence} for each of the atoms thus bonded.
Contrasted with {hydrogen bond}, which is weaker and does
not satisfy the valence of either atom involved.

{double bond}, {triple bond}, a {covalent bond} which
involves the merging of orbitals of two (or three)
electrons on each of the two connected atoms, thus
satisfying two (or three) units of valence on each of the
bonded atoms. When two carbon atoms are thus bonded, the
bond (and the compound) are said to be unsaturated.

{Bond debt} (Law), a debt contracted under the obligation of
a bond. --Burrows.

{hydrogen bond}, a non-covalent bond between hydrogen and
another atom, usually oxygen or nitrogen. It does not
involve the sharing of electrons between the bonded atoms,
and therefore does not satisfy the valence of either atom.
Hydrogen bonds are weak (ca. 5 kcal/mol) and may be
frequently broken and reformed in solution at room
temperature.

{Bond of a slate} or {lap of a slate}, the distance between
the top of one slate and the bottom or drip of the second
slate above, i. e., the space which is covered with three
thicknesses; also, the distance between the nail of the
under slate and the lower edge of the upper slate.

{Bond timber}, timber worked into a wall to tie or strengthen
it longitudinally.
[1913 Webster +PJC]

Syn: Chains; fetters; captivity; imprisonment.