Unit 2: Molecular and Ionic Compound Structure and Properties

chemical bonds

the attractive forces that hold atoms together

ionic bond

A chemical bond resulting from the attraction between oppositely charged ions.

covalent bond

A chemical bond that involves sharing a pair of electrons between atoms in a molecule

metallic bond

a bond formed by the attraction between positively charged metal ions and the electrons around them

Lewis symbol

the representation of an atom that shows valence electrons as dots around the symbol of the element

octet rule

States that atoms lose, gain or share electrons in order to acquire a full set of eight valence electrons

lattice energy

the energy released when one mole of an ionic crystalline compound is formed from gaseous ions

single bond

a covalent bond in which two atoms share one pair of electrons

double bond

A covalent bond in which two pairs of electrons are shared between two atoms

triple bond

a covalent bond in which two atoms share three pairs of electrons

bond length

the average distance between the nuclei of two bonded atoms

bond polarity

a measure of how equally or unequally the electrons in any covalent bond are shared

polar covalent bond

A covalent bond in which electrons are not shared equally

nonpolar covalent bond

a covalent bond in which the electrons are shared equally by the two atoms

Electronegativity

A measure of the ability of an atom in a chemical compound to attract electrons

polar molecule

A molecule that has electrically charged areas.

Dipole

created by equal but opposite charges that are separated by a short distance

formal charge

The number of valence electrons in an isolated atom minus the number of electrons assigned to the atom in the Lewis structure

resonance structure

one of the two or more equally valid electron dot structures of a molecule or polyatomic ion

bond angle

the angle formed by two bonds to the same atom

VSEPR theory

Valence-shell electron-pair repulsion theory; because electron pairs repel, molecules adjust their shapes so that valence electron pairs are as far apart as possible

electron domain

in the VSEPR model, a region about a central atom in which an electron pair is concentrated

bonding pair

an electron pair found in the space between two atoms

nonbonding pairs

two paired valence electrons that tend not to participate in a chemical bond

bond dipole

separation of electrical charge created when atoms with different electronegativities form a covalent bond

hybrid orbitals

orbitals of equal energy produced by the combination of two or more orbitals on the same atom

Hybridization

the mixing of several atomic orbitals to form the same total number of equivalent hybrid orbitals

sp hybridization

linear; bond angle: 180

a type of bonding where the 2s orbital mixes with only one of the three p-orbitals resulting in two sp orbitals and two remaining unchanged p orbitals

sp2 hybridization

1. Trigonal planar structure

2. sp2 hybridization creates 3 identical orbitals of intermediate energy and length and leaves one unhybridized p orbital

3. 3 effective pairs of electrons surround the carbon (double bond treated

as one effective pair)

sp3 hybridization

A type of hybridization that results from the combination of the s orbital and all three p orbitals in the second energy level of carbon, resulting in four hybrid orbitals and occurs when a carbon atom is bonded to four other atoms. The geometric arrangement of those four hybrid orbitals is called tetrahedral.

sigma bond

a bond formed when two atomic orbitals combine to form a molecular orbital that is symmetrical around the axis connecting the two atomic nuclei

pi bond

a bond that is formed when parallel orbitals overlap to share electrons.

metallic solids

solids that have metal atoms occupying the crystal lattice and held together by metallic bonding

ionic solids

solids whose composite units are ions; they generally have high melting points

covalent network solids

solids in which the units that make up the three-dimensional network are joined by covalent bonds

molecular solids

solids whose composite units are molecules

crystalline solid

A solid that is made up of crystals in which particles are arranged in a regular, repeating pattern

amorphous solid

A solid made up of particles that are not arranged in a regular pattern

Alloys

a mixture composed of two or more elements, at least one of which is a metal

substitutional alloy

some of the host metal atoms are replaced by other metal atoms of similar sizes

interstitial alloy

a mixture formed when small atoms fill holes in a metallic crystal

electron sea model

Proposes that all metal atoms in a metallic solid contribute their valence electrons to form a "sea" of electrons, and can explain properties of metallic solids such as malleability, conduction, and ductility.