Chemical Bonds - Denton Independent School District...Chemical Bonds Student notes for Pre-AP...

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