Chem 142 Midterm 1 [UW Colleen Craig]

Standing wave

A wave that oscillates in time but does not translate through space

Excited State

a state in which an atom has more energy than it does at its ground state

Wavelength of a particle equation

λ = h/mv

λ

wavelength

m

mass

v

velocity

Joule in expanded units is...

kgm^2/s^2

black body radiation

radiation off of a heated object [like yourself]

why does black body radiation appear continuous

Because the energy levels are so close, any ΔE is possible

E

energy

Node

A point of zero amplitude on a standing wave

Energy equation

E=hv

h

Planck's constant : 6.626 * 10^-34 Js

nu

frequency

photon

quantity 'hv'

Speed of light equation

C = λv [nu]

Valence Shell

outermost shell of an atom

If the Valence Shell is full

The atom is most stable [especially if s & p orbitals are the highest]

Why do blackbody radiators appear continuous?

Becasue the energy levels are so close

Quantization

occurring only in specific discrete values, not continuous

blackbody radiation

emission of light from hot objects

isoelectronic

having the same number of electrons

stable Lewis structures

- Octet rule must be satisfied on every atom

- No or minimized FC

- If FC- like charges apart and opposite charges together

Total nodes

n-1

Radial nodes

n-l-1

Angular nodes

l

n quantum number

principal energy level/shell

l quantum number

shape of orbital

between 0 and n-1

ml quantum number

orientation in space

between or equal to 1 and -1

ms quantum number

the spin

+/- 1/2

what is the n and l for something in the 3p orbitals

n = 3

l = 1

degenerate orbitals means

orbitals with the same energy

How many maximum electrons can you hold in n=3

18

bc, l = n-1, so 0,1,2: 2+6+10=18

s,p,d,f

1,3,5,7

Wave Particle duality

electrons and light can behave as both a wave and a particle

Atomic Spectrum of Hydrogen

When the emission spectrum of hydrogen in the visible region is passed through a prism, only a few lines are seen.

Absorption spectrum

Shows dark lines where the substance [atoms] between the source and detector absorbed the wavelengths.

emission spectrum

- a spectrum of the electromagnetic radiation emitted by a source.

- atoms can ONLY absorb EM energy at these discrete wavelengths

Bohr's Atomic Model

Proposed that the quantized spectrum from hydrogen was due to the electron moving between discrete energy states

Whats the relation between energy and wavelength?

inverse

define "relaxing"

Means going down an energy level [closer to the nucleus]

E=0 at n=

infinity, because there is no interaction between the electron and the nucleus., meaning that the electron has really high energy.

Why does the Bohr Model fail?

The Bohr model is based on the energy levels of one electron orbiting a nucleus at various energy levels. Any other electrons in the atom will repel the one electron and change its energy level.

Rydberg Equation

used to calculate the wavelengths of all the spectral lines of hydrogen

J=

kgm^2/s^2

ionization energy

The amount of energy required to remove an electron from an atom

Ground State

The lowest energy state of an atom

n=1

standing wave

a wave that appears to stand in one place, even though it is really two waves interfering as they pass through each other

Ervin Schrodinger and Louis De Broglie did what

exploited wave-particle duality to describe mater and energy in terms of wave mechanics

de Broglie equation

λ = h/mv

An electron can adopt only certain "standing wave" patterns of motion when...

subjected to a constraining potential

amu to mass

divide the amu by the Atomic Mass Unit to get it into grams

Ionization energy trend

increases up and to the right

Affinity energy trend

increases up and to the right

Size of atom trend [atomic radius]

Increases down and to the left

Electronic spin

- "They BEHAVE AS IF it were a bundle of spinning energy"

- Spin to the right as up, spin to the left as down

Hund's Rule

states that single electrons with the same spin must occupy each equal-energy orbital before additional electrons with opposite spins can occupy the same orbitals

orbitals are filled in order of...

increasing energy, not n

In multi electron atom, the orbitals in the same n level are not degenrate because of...

electron-electron repulsion

Aufbau Principle

An electron occupies the lowest-energy orbital that can receive it

Period (periodic table)

horizontal row

Groups (periodic table)

vertical columns

Valence shell

outermost shell of an atom

Pauli Exclusion Principle

An atomic orbital may describe at most two electrons, each with opposite spin direction

Dipole

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

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

ionic bond

Formed when one or more electrons are transferred from one atom to another.

metal and non metal

covalent bond

non metal and non metal

Resonance Structures

same atomic linkages, different bonding (single vs double) Real structure is an "average" of the available resonance structures

Structural Isomers

different atomic linkages. "Formal Charge" is used to determine most likely structure Conceptually, we think of the bonding as an average of these two structures

octet rule

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

duet rule

the observation that atoms such as hydrogen form stable molecules when they share two electrons

In a polyatomic molecule, teh center atom is usually...

- least electronegative

- make the most number of bonds

terminal molecule

it NEVER forms more than one bond

Formal Charge

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

Valence Shell Expansion

- For third row elements the energetic proxiity of the d orbitals means these orbitals can participate in bonding

- Why this occurs, more than 8 electrons can surround in a third-row element

- Typical atoms that demonstrate valence shell expansion are PS and large halogens (CL, BR, I)

molecular geometry (VSEPR)

shape of a molecule, based on the relative position of the atoms

Molecular geometry 2,3,4

linear, trigonal planar, tetrahedral

Basic VESPR Model steps

- Construct the lewis dot structure

- Arrange bonding/lone electron pairs, such that repulsion is minimized

- Name the structure from the position of the atoms

Valence Shell Electron Pair Repulsion Theory

The shape is created based off the electron pairs such that the least repulsion between them is possible

Light spectrum

Radio waves, microwaves, infrared, ROYGBIV[visible], ultraviolet, X-rays, gamma rays

The the two metals with a low boiling point are...

Mercury and Gallium [Cesium can metal in your hand ]

The most important info from the periodic table [according to Zumhdal]

is electronic configuration

Electronic affinity

The energy change associated with the addition of an electron to a GASEOUS ONLY atom

Koopman Theorem

The ionization energy of an electron is equal to the energy of the orbital from which it came

S

M

L

S -violet to green

M-blue to orange

L-green to red

ROYGBIV backwards

S: 400-500

M:450-630

L:500-700