Chemistry Unit 6 - Chemical Bonding

Chemical Bond

mutual attraction between nuclei and valence electrons of different atoms that binds the atoms together

How do atoms bond?

Through electrical attraction

Why do atoms bond?

To achieve greater stability (less potential energy) and fill their valence shell

Ionic bond

electrical attraction between cations (+ ions, metals) and anions (- ions, nonmetals) where cations give electron(s) to anions

Covalent bond

electrons shared between two atoms

bone is generally not a pure covalent bond

between nonmetals

How can bond types be predicted?

compare electronegativity values

higher electronegative atom has stronger attraction for electrons

Nonpolar Covalent bond value

[0, 0.4]

Polar covalent bone value

(0.4, 1.7)

Ionic bond value

greater than 1.7

δ+ meaning

partial positive

bond length

distance between bonded atoms at minimum potential energy

bond energy

energy required to break chemical bond and form neutral isolated atoms

How do shared electrons modify orbitals?

orbitals overlap

octet rule

atoms tend to form compounds so that each has 8 electrons in its valence shell

exceptions to octet rule

hydrogen (1 bond), helium (2 electrons to obtain stability), beryllium (2 bonds), boron (3 bonds)

expanded octet

atoms can accommodate more than 8 electrons (sulfur, phosphorus, etc.)

a single covalent bon involves the sharing of…

two electrons

ionic compound

combination of positive and negative ions to form a neutral compound with equal positive and negative charges

formula unit

lowest possible ratio of elements in an ionic compound

crystal lattice structure

3D arrangement of cations and anions attracted to each other

lattice energy

energy requires to break apart the crystal lattice

ionic compound characteristics

high melting points, brittle, hard, conductive in liquid state

molecular compounds

independent, neutral units

molecular compound characteristics

low melting and boiling points, less brittle, non-conductive

metallic bonding

a type of chemical bonding that occurs between metal atoms, characterized by a sea of delocalized electrons

sea of electrons

mobile electrons surrounding metal atoms to form a metallic bond

properties of metals

shiny, malleable, ductile, conductive , strong metallic bond

VSEPR

valence shell electron pair repulsion

predicts molecular geometry based on electron pair repulsion

Hybridization

“mixing” atomic orbitals to form new orbitals

number of hybrid orbitals formed = number of atomic orbitals mixed

dipole

asymmetrical distribution of electrons in molecule

net dipole = polar molecule

no net dipole = nonpolar molecule

dipole-dipole force

attraction between polar molecules

dipole-induced dipole

polar molecule induces dipole on another atom

hydrogen bonding

H-N, H-O, H-F

strong force resulting from H bonding to electronegative atoms

london dispersion forces

temporary force of nonpolar molecules due to electron movement

2 electron domains

linear

2 electron domains, 2 bonding domains, 0 nonbonding domains

linear (180°)

3 electron domains

trigonal planar

3 electron domains, 3 bonding domains, 0 nonbonding domains

trigonal planar (120°)

3 electron domains, 2 bonding domains, 1 nonbonding domains

bent (<120°)

4 electron domains

tetrahedral

4 electron domains, 4 bonding domains, 0 nonbonding domains

tetrahedral (109.5°)

4 electron domains, 3 bonding domains, 1 nonbonding domains

trigonal pyramid (107°)

4 electron domains, 2 bonding domains, 2 nonbonding domains

bent (104.5°)

5 electron domains

trigonal bipyramid

5 electron domains, 5 bonding domains, 0 nonbonding domains

trigonal bipyramid (120° and 90°)

6 electron domains

octahedral

6 electron domains, 6 bonding domains, 0 nonbonding domains

octahedral (90°)

2 electron domains hybridization

sp

3 electron domains hybridization

sp²

4 electron domains hybridization

sp³

5 electron domains hybridization

sp³d

6 electron domains hybridization

sp³d²