AP CHEM UNIT 2 NOTES

Electronegativity

the tendency for an atom to attract an electron while in a chemical bond (must be comparitive)

When an atom has both a high ionization energy and a high electron affinity, it will have?

high electronegativity in a chemical bond

which is the most electronegtaive ?

Flourine

the least electrongetaivte?

FrankiumFrancois

What does electronegtaivity do across a period?

increase

what does electronegativity do down a group?

decrease

mettalic

nuclei of metal atoms are attracted to delocalized electrons that move in a swarm

ionic

metals transfer electrons to a non metal to form ions that are electrotastically attracted and form a lattice structure

covalent

the oribitals in non metal atoms overlap and share electrons

non-polar covalent

the electrons are shared equally between atoms (the electrical charge is = districuted)

polar covalent

the electrons are sgared unequally between atoms (uneven districution)

partial pos charge

low electronegativity

partial neg charge

high electronegtaivuty

dipole moment

dipole arrow points toward more electronegative atom. It is a vector quantity that represents the polarity of a bond.

0-0.4 bond difference?

nonpolar covalent

0.4-1.7 bond difference?

polar covalent bond

1.7-3.3 bond difference?

ionicbond

properties of metallic

electrons delocalized from nuclei, high melting and boiling point, good conductivity, shiny, malleable

properties of ionic

electrons transferred between ions, very high melting and boiling points, conducts when melted or dossolved, brittle

polar covalent properties

electrons shared unequally, low boiling and melting points, poor conductor

nonpolar covalent

electrons shared equally, very low melting and boilin gpoint, poor conductor

metallic

ionic

polar covalent

nonpolar covalent

why do bonds form between atoms?

decrease PE and become more stable

bond length

the distance between atoms at the point of equilibroum between repulsion and attractive forces

what happens to PE at close distances

repulsion causes high PE

what happens to pe at far distances

attractive forces increase

when is pe at minimum

the attractive and repulsive forces balance each other

bond energy

the energy needed to break a chemical bond

bonds with higher energy

have smaller bond lengths and are more stable than bonds with lower energy.

the weaker the coloumbic force and the lower the bond energy

the larger the distance between atoms

the greater difference in coulombic force and the higher the bond energy

the larger the electronegativity

bond order

the number of bonding electron pairs at a bonding sites

sigma bond

a bond forms w/ maximum overlap between orbitals (all single bonds)

pi bond

a bond forming from the overlap of two different lobes of orbitals

as bond order increases

the bond length decreases while the bond energy increases

single bond consists of

1 sigma bond - 2 electrons - 1 bond order

double bond consists of

1 sigma bond and 1 pi bond - 4 electrons - 2 bond order

triple bond

1 sigma bond and 2 pi bonds - 6 electrons - 3 bond order

largest bond length and smallest bond energy

smaller bond length and larger bond energu compared to single bonds

smallest bond length and largest bond energy for a bond type.

lattice energy

the energy required to separate one mole of an ionic compound into its gaseous ions. It reflects the strength of the ionic bonds within the crystal lattice.

when does lattice energy increase

the charges if ions increase, the radius of ions decreases

property of bonds with high LE

stronger/harder materials, higher melting points, lower solubility

when does the strength of a metallic bond increase

increasing cation charge and the # of valence electrons and decreasing cation radius

alloy

a mixture containing at least one metal

substitutional alloy

an alloy composed of atoms of similar sizes

interstitial alloy

an alloy composed of atoms of different sizes

Lewis symbol

an element or ion symbol that uses a dot to represent a valence electron

odd number of electrons LDS

it is impossible to satisfy the octet rule if the number of valence electrons is uneven

incomplete octet

it isimpossible to satisfy the octet rule because the valence shell does not have a full complement of eight electrons.

a more dominant LDS structure has a?

formal charge closes to zero and the negative formal charges are on the more electronegative atoms

formal charge

the theoretical charge assigned to an atom in a molecule, based on the assumption that electrons in a bond are shared equally.

calculate formal charge

valence electrons - 1/2(bonding electrons) - nonbinding electrons

resonance

a phenomenon where a molecule can be represented by two or more valid Lewis structures, differing only in the placement of electrons.

drawing resonance

just change where double/triple bonds are

bond order

number of lines(bonds) - number of connections (to atoms)

hypervalent species

central atoms in period 3 or lower in the periodic table are large enough to bond with more than 5 valence electrons

LDS drawing tip

when there is a charge, you must subtract/add those electrons from the total to draw the striucture

VSEPR theory

the Valence Shell Electron Pair Repulsion theory, which predicts the geometry of molecules based on electron pair repulsions.

electron geometry

an area of electron densiry - depends on # of electron domains

electron domain

an area of electron density (all bonds)

a molecule is polar if

the bond dipoles unevenly cancle out

a molecule is nonpolar if

the bond dipoles evenly cancel out.

molecules w/ symmetrical geometries

are nonpolar when all the attarcted atoms are the same

molecular geometry

the three dimensional arrangement of a molecule in space

linear

trigonal planar

Bent

tetrahedral

trigonal pyramidal

bent

Trigonal Bipryamidal

seesaw

T-shaped

linear

octahedral

square pyramidal

square planar

T-shaped

linear

hybridization

process where electron orbitals w/ similar energies mix to form new orbitals of equal energies

hybrid orbitals

oribitals of equal energy produced through the combination of orbitals on the same atom

which are stronger, pi or sigma bonds

pi bonds are weaker due to less oribital overlap, they are only present with sigman bonds

the presense of pi bonds lead to ?

structural isomers

structural isomers

compounds with the same moleculra formula but different structures