Molecules/Energy/Polarity

In bonded atoms, are electrons usually shared equally

Unless the two atoms are identical, one atom typically has more electron-attracting power (or electronegativity) then the other

What happens to an atom with a higher electronegativity in a molecule

it has a negative partial charge because it is "holding on to" more than half of the electrons being shared in the molecule

What happens to an atom with a lower electronegativity in a molecule

it has a positive partial charge because it is "holding on to" less than half of the electrons being shared in the molecule

Name and bond angle of molecule with a steric number of 2

linear; 180; non-polar

What is the relationship between electron density and bond order

more electrons= higher bond order

Partial Charge equation

partial charge= Va-Na-paBa Va= number of valence electrons Na= number of unbonded electrons (loan pairs) pa= (ENa/ENa+ENb) Ba= number of bonding electrons (number of bonds)

What phase of matter has the strongest intermolecular forces

solid

Name and bond angle of molecule with a steric number of 4

tetrahedral; 109.5; non-polar

Enthalpy

the amount of energy released or absorbed in a chemical process; represented by ΔH

Bond energy

the energy required to break 1 mol of a specific chemical bond

If two covalent bonds are compared, how is it determined which is more polar

the one that results in partial charges with larger magnitude is considered more polar

What must the magnitudes of the different atoms' partial charges in a molecule equate to

the overall net charge of the molecule; thus if the net charge is zero the magnitude of both atom's partial charges must be equal

What is the relationship between bond order and bond length

the smaller the BO the longer the bond length

What does it mean when ΔH is negative

there is a release of energy during a chemical process and the reaction is exothermic

What is the relationship between AVEE and EN

they are proportional with one another with some slight deviation. On avg. the difference between EN and AVEE is a factor of 1.8

Name and bond angle of molecule with a steric number of 3

trigonal planar; 120; non-polar

Name and bond angle of molecule with a steric number of 4 loan pair 1

trigonal pyramidal; 109; polar

Endothermic reaction

when energy (heat/light) is absorbed

exothermic reaction

when energy is released (usually in the form of heat or light)

dipole moment equation and explanation of variables

μ= q * d μ= dipole moment q=magnitude of the two charges d= the distance (vector) between two charges

Bonds that have a higher bond energy...

Are stronger bonds

What is the "best" lewis structure

-the one with the fewest charges

7-Step method

1) Electrons needed for Octet/Duet rule2) Valence electrons3) Electrons shared= #1-#24) Bonds= #3/25) Add loan pairs6) Partial charge (higher X = partial charge negative; lower x = partial charge positive)7) Formal charges= valence electron- electrons assigned (box)

How do you draw a reaction energy diagram

1) consider the reaction taking place 2) break apart all of the reactant molecules and calculate their ΔH. Pay attention to coefficients 3) represent the atoms in terms of their moles 4) resemble those atoms into the product molecules and calculate their ΔH. Pay attention to coefficients 5) Calculate difference between the ΔH values

covalent bond

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

polar covalent bond

A covalent bond in which electrons are not shared equally; there is a difference in electronegativity between the atoms

Electronegativity

A measure of the ability of an atom to attract electrons

Equation for AVEE and description of its components

AVEE= (aIs+bIp) /(a+b) a and b are the numbers of electrons in the s and p subshells of the valence see, Is and Ip are the ionization energies of those subshells

What is the periodic trend of AVEE and why

Across period: increases as you move right to left b/c core charge/nuclear charge increases Down a row: decreases because distance from nucleus increases

Why do homonuclear molecules have non polar bonds

Because there is no difference in electronegativity

How do you calculate bond order for regular lewis structures and resonance structures

Both: count the number of bonds and divide that number by the number of regions they are in

How to determine if you can expand an octet

Check to see if valence electron capacity for central atom has been reached. If not, you can rearrange the number of bonds used

How can a lewis structure demonstrate covalent and ionic bonds

Covalent: Based on the electron density-if the different atoms are all connected within the "cloud" of electron density Ionic: Based on the electron density- when the atoms of the lewis structure are detached and in separate "clouds" of electron density Ionic also based on charges : + and - charge indicate ionic

Is breaking bond endo or exothermic? Why?

Endothermic because energy is needed (or absorbed) too break atoms, being held together by bonds, apart

Is bond forming endo or exothermic? Why?

Exothermic because when bonds are formed they release energy (the same amount of energy required to break them)

exceptions to the octet rule

H= 2 electronsBe= 4 electronsB= 6 electrons

What does the average ionization energy of the valence electrons tell you/give insight to?

How tightly an atom holds its valence electrons Higher a valence electron's ionization energy, harder to remove it/tighter it is held

In terms of AVEE why is Na more likely to become NA+ than O is to form O+

O AVEE is greater than Na AVEE. More energy is required to remove an e from O than Na

What is the periodic trend of electronegativity

Same as AVEE

Why does H(g) has a ΔH=0 and H2(g) has a ΔH=-435.30?

There is no change in enthalpy b/c there is no chemical change in the production of H(g)

non polar covalent bond

a bond between identical atoms

dipole moment

a measure of the separation and magnitude of the positive and negative charges in polar molecules

Name and bond angle of molecule with a steric number of 3 loan pair 2

bent; 109; polar

Name and bond angle of molecule with a steric number of 3 loan pair 1

bent; 120; polar

What does it mean when ΔH is positive

energy is being absorbed during a chemical process and the reaction is endothermic

How do you calculate bond length for resonance structures

find the average of the lengths of different bonds associated with the structure

Intermolecular forces

forces of attraction between molecules

What phase of matter has the weakest intermolecular forces

gas

Atoms with a smaller atomic radius...

have shorter bonds and are therefore stronger