ap chem unit 2

bro you're cooked

Electronegativity

The ability of an atom to attract shared electrons in a bond.

Coulomb's Law and EN

EN depends on nuclear charge and distance to electrons so more protons and smaller radius increase electronegativity.

EN trend down a group

Electronegativity decreases down a group because atoms get larger and inner electrons shield outer electrons.

EN trend across a period

Electronegativity increases across a period because nuclear charge increases and atomic radius decreases.

Nonpolar covalent bond

Equal sharing of electrons between atoms with similar electronegativity for example C C or H H.

Polar covalent bond

Unequal sharing of electrons that creates partial charges for example H O or C F.

Ionic bond

Transfer of electrons from a metal to a nonmetal forming cations and anions.

Metallic bond

Valence electrons are delocalized in a sea of electrons that binds metal cations together.

Bond polarity and EN difference

Greater difference in electronegativity leads to more polarity and a larger dipole moment.

Approximate EN difference guide

Small difference implies nonpolar moderate difference implies polar and large difference suggests ionic though it is a continuum.

Partial charges δ+ and δ-

Polar bonds create small positive and negative charges on atoms shown as delta plus and delta minus.

Dipole moment

A measure of bond polarity pointing from positive to negative center.

Continuum of bonding

Bonding ranges from covalent to ionic with degrees of mixed character rather than a sharp divide.

How to predict bond type

Use element types and electronegativity check for metal plus nonmetal ionic and nonmetal plus nonmetal covalent.

Ionic compound properties

Brittle solid high melting point soluble in water conducts electricity when molten or dissolved.

Covalent compound properties

Often low melting point do not conduct electricity and can be gases liquids or solids.

Metallic compound properties

Good conductor malleable ductile and shiny due to mobile electrons.

Valence electrons

Electrons in the outermost shell that participate in bonding and determine reactivity.

Sea of electrons

Description of metallic bonding where electrons are free to move among metal ions creating conductivity.

Electronegativity and Coulomb's law

Stronger nuclear charge and closer electron distance increase attraction for electrons and raise EN.

Deciding ionic vs covalent

Look at element types and properties like conductivity solubility and melting point to classify bonding.

Order of increasing polarity

C C < C H < C O < C F < Ca C.

Classify H2

Nonpolar covalent equal sharing of electrons.

Classify CH4

Nonpolar covalent C H bonds are effectively nonpolar.

Classify H2O

Polar covalent O is delta minus H is delta plus giving a molecular dipole.

Classify NBr3

Polar covalent N is delta minus Br is delta plus with bond dipoles that may not cancel.

Classify NaF

Ionic bond forming Na plus and F minus with high lattice energy.

Classify ZnCl2

Ionic compound zinc cations and chloride anions form a salt.

Classify CuZn

Metallic alloy with delocalized electrons and metallic properties.

Classify Al

Metallic bonding in the solid metal with conductivity and malleability.

Bond dipole vs molecular dipole

Bond dipoles may cancel depending on molecular geometry and give no net molecular dipole.

Using properties to identify bonding

Check melting point solubility and conductivity to decide if bonding is ionic covalent or metallic.