Chemical Bonding & Molecular Theory

chemical bonding

when electrons frm different atoms interact with each other

bond length

distance between two nuclei at the point of minimum energy

types of bonds

ionic and covalent

valence electrons

electrons that can participate in the formation of a chemical bond

compounds

formed when two or more atoms of different elements chemically combine. they can’t be separated through mechanical means.

ionic bond

• formed by the transfer of electrons from one atom to another.

• caused by a positive ion (cation) and negative ion (anion).

• non-metal and metal atoms.

• forms crystals because of their strong bond.

• poor conductors when solid, good conductors when dissolved in water.

covalent bond

• formed when atoms share valence electrons to achieve a full outer shell.

• more soft and relatively flexible compared to ionic compounds.

• may are insoluble in water but those that dissolve don’t conduct electricity.

• has two kinds of covalent bonds; polar and non-polar.

polar covalent bond

• occurs between atoms with different electronegativities.

• one side of the compound has a higher electronegativity, where most valence electrons “hog” over.

• leads to partial charges and a dipole moment.

dipole moment

• separation of positive and negative charges in a molecule.

• occurs in polar molecules because of the uneven distribition of electron density.

nonpolar covalent bond

• atoms have identical or nearly similar electronegativity charges.

• charges are distributed evenly in the compound.

metallic bond

• forms when free electrons are shared by two metallic atoms.

• have moderately high melting points.

• malleable and ductile.

• good conductors of heat and electricity.

electron transfer

when one atom loses and electron and another atom gains the electron.

octet rule

the tendency of atoms to prefer to have eight electrons in the valence shell.

lewis dot symbol

the chemical symbol of an element surrounded by dots equal to the number of valence electrons present in the atoms of the element

Ns2Np6

• noble gas configuration.

• best exemplifies octet rule

lewis structure

a combination of lewis symbols that represents either the transfer or the sharing of electrons in chemical bonds

-ion

the suffix of common nonmetallic ions in ionic bonding.

VSEPR

• valence shell electron pair repulsion theory

• a set of procedures for predicting the molecular geometry of a molecule using the information contained in the molecule’s Lewis structure.

kinetic molecular theory

describes the miscroscopic properties of matter and how they translate to the state of other properties of matter.

statements of the kinetic molecular theory

• matter is composed of small particles

• molecules interact with one another through attractive forces

• molecules are always in constant random motion

intermolecular forces

• attractive forces between moecules

• the stronger the interaction, the smaller the distance

• solids; strong imf. liquids'; intermediate imf. gases; negligible

kinetic energy

• energy of the particles in motion

• the higher the kinetic energy, the more active the particles are

temperature

• measure of the average kinetic energy of molecules

• can be used to describe phase changes

ion-ion interaction

• interaction between two oppositely charged particles

• ionic bond holds together the particles in the ionic compound

ion-dipole interaction

• result of the electrostatic attraction of a molecule containing a dipole and an ion

• responsible for the dissolution of most ionic solids in polar solvents

• strength of imfa increases as the charge of the ion increases

hydrogen bond

• between polar molecules where on of the molecules has a hydrogen attached

• bonds with F, O, or N

• strongest type of dipole-dipole force

dipole-dipole forces

attractive force between polar molecules

dipole-induced-dipole force

attractive forces between polar and a nonpolar (neutral) molecule

london-dispersion force

• attractive forces between nonpolar molecules

• present in all particles or molecules

• weakest type of imf

van der waals

sum of all the attractive and repulsive forces between and with molecules

weakest to strongest imf

london dispersion < dipole-dipole < hydrogen bonding < electrostatic interactions

electrostatic interactions

ion-ion, ion-dipole, dipole-dipole, dipole-induced-dipole

stronger IMF

translates to greater surface area, higher melting/boiling point, greater viscosity, lower vapor pressure

crystalline formation

when IMFA creates a regular structural pattern

vapor pressure

• tendency of surface liquid to escape from the bulk liquid

• pressure exerted by a vapor in an equilibrium with its liquid phase in a closed system

• molecules with a stronger IMF have less tendency to escape into gas

boiling and melting point

condition at which boiling occurs based on the vapor pressure

capillarity

• tendency of liquids to rise or fall within a narrow tube

• phenomenon where liquids rise spontaneously in a cpillary

cohesion

attraction between like substances

viscosity

• a liquid’s resistance to flow

• molecules with a stronger IMF have greater resistance to flow

diffusion

spreading out of liquid particles to occupy available space

heat capactiy

heat required to raise the temperature of 1g of a substance by 1 degree

specific heat capacity

amount of heat required to raise the temperature of 1g of a substance by 1 degree Celsius

• water: 4.18 (J/g x C)

critical point

conditions in which the liquid and gaseous phase of a substance becomes indistinguisible

adhesion

attraction between unlike substances