Chemical Bonds concept 2.3

Chemical bond

Attraction that holds atoms together

Covalent bond

Bond formed by sharing electrons

Molecule

Two or more atoms held together by covalent bonds

Single covalent bond

One shared pair of electrons

Double covalent bond

Two shared pairs of electrons

Valence

Bonding capacity of an atom

Valence of carbon

four

Electronegativity

Ability of an atom to attract electrons

Nonpolar covalent bond

Electrons shared equally

Polar covalent bond

Electrons shared unequally

Partial charges

δ− and δ+ in polar molecules

Ionic bond

Bond formed by transfer of electrons

Ion

Charged atom or molecule

Cation

Positively charged ion

Anion

Negatively charged ion

Water effect on ionic bonds

Water weakens ionic bonds by reducing attraction

Importance of weak bonds

Allow reversible interactions essential for life

Hydrogen bond

Attraction between a hydrogen atom and an electronegative atom

Where hydrogen bonds form

Between molecules or within large molecules

van der Waals interactions

Weak attractions from temporary charge differences

Importance of molecular shape

Shape determines biological function

What determines molecular shape

Arrangement of electron orbitals

Tetrahedral shape

Common shape of carbon-based molecules

Water molecule shape

V-shaped (104.5° angle)

Shape specificity

Molecules interact based on complementary shapes

Chemical reaction

Process that breaks and forms chemical bonds