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Chemical Bonds
Student notes for
Pre-AP Chemistry
Chemical Bond is
link between atoms that results from mutual attraction of their nuclei for the electrons.
classified by the way the valence electrons are distributed around the nuclei of the combined atoms.
the bond usually results in a lower energy state in the bonded atoms rather than the individual atoms.
Energy Flow of bonds
Breaking bonds energy absorbed
Forming bonds energy released
3 Types of Chemical Bonds
Ionic Bond
Covalent Bond
Metallic Bond
Ionic Bonds
involves a transfer of valence electrons.
chemical bond results from electrostatic
attraction between positive and negative ions.
Ionic Compounds
made of positive and negative ions.
Positive and negative charges must be
equal.
forms crystalline structures.
known as salts
representative particle is called a formula
unit. A formula unit is the simplest whole
number ratio of ions in an ionic compound.
Common Characteristics of Ionic
Compounds
high melting point and boiling point.
hard and brittle crystalline solids.
many are soluble in water.
good conductors of electricity when in the
molten state or dissolved in water.
Metallic Bonds
properties of metals are very different than
ionic or covalent compounds.
metal atoms contain a smaller number of
valence e than vacant in highest energy
level orbitals.
Metal atoms have
relatively low ionization energies and
electronegativities.
room in vacant highest energy level
orbitals to share many electrons from
surrounding atoms.
e are delocalized.
all valence e are shared by all the
atoms.
Metallic Bonds
chemical bond resulting from the attraction
between positive ions and surrounding
mobile electrons.
Strength of bond varies with nuclear
charge and number of valence electrons.
Characteristics of Metallic Bonds
high electrical conductivity
high thermal conductivity
Malleability
Ductility
high luster
Covalent Bonds
involves a sharing of valence electrons
electron clouds overlay causing an
increase in e cloud density
attraction of nuclei to high e density
region holds atoms together
Covalent Compounds
made of atoms
forms solids, liquids, and gases
representative particle is called a
molecule. A molecule is the smallest unit
quantity of a compound which can exist by
itself and retain ALL the properties of the
original substance.
Common Characteristics of
Covalent Compounds
low melting point and boiling point
poor conductor of electricity
can be solids, liquids, or gases
many are insoluble in water
Octet Rule
compounds form so that each atom, by
gaining, losing, or sharing electrons, has
an octet (8) electrons in the highest
occupied energy level
Lewis Structures
uses dots to represent e
dot-pairs or dashes represent bonding pair
between atoms
dot-pairs adjacent to only one atom
represents non-bonding pairs (unshared
pairs, lone pairs)
Single Bond
sharing of one pair of electrons between two
atoms
Double Bond
sharing of two pairs of electrons between
two atoms
Triple Bond
sharing of three pairs of electrons between
two atoms