Exam 2 Chem

1 cal

4.184 J = 4.184 J/g*C

1000 calories

1 kcal = 1 Cal (food)

Exothermic

heat is released from the "system" (the reacting substances) into the "surroundings"

Endothermic

where a system absorbs heat energy from its surroundings

State function

Does not matter how you got there

Change in enthalpy

Extensive property

Heat of fusion

Melting

Heat of vaporization

Boiling

Qsys= -Qsurr

Qmetal= -Qwater

Enthalphy aka delta h

= qrxn/quantity (mols)

Bomb calorimeter

qrxn = -(qbomb + qwater)

qbomb

Cbomb * delta T

If no mass or water of a solution are given, solve for qbomb

qrxn = -qbomb

Coffee cup calorimeter

qrxn = -(qbomb + qsol)

Hz

1/s or s-1

Nm

1×10^-9 m

Pm

1×10^-12 m

Å

1 × 10^10 m

Amplitude relates to

Brightness

Visible light wavelengths

400nm (violet) to 750 nm (red), green light is shorter than red

Electromagnetic spectrum increasing frequency

Radio, microwaves, infrared, visible light, uv, X-ray, gamma rays

As an object is heated up, the light it emits changes from red to

Light blue

Photoelectric effect

Light of sufficient frequency shines on a metal surface and a current flows

Delta E of an atom is the same for E of photon

= hv or hc/y

Energy of radiation (photons) units

J/photon

Energy levels (n) also called

Stationary states

The smaller the n value,

The smaller the radius of the orbit, and the smaller the energy level

The electron in the atom does not radiate energy while

In orbit around the nucleus

Energy level n=1 can absorb a proton and go to n=2 if

The photon has the same amount of energy as (n2-n1)

Ionize

When an electron is ejected from an atom, final = infinity

Emission

Higher to lower

Absorption

Lower to higher

Rydberg equation

1/y=R(1/(n1)²+ 1/(n2)²), where n2 > n1 (wavelength in meters)

Lyman series produces UV

Terminates at n=1, 90-100nm

Balmer series produces visible light

Terminates at n=2 400-750nm

Infrared

Terminates at n=3 1000’snm

When electrons in the hydrogen atom drop from outer orbits to three specific energy levels,

Spectral lines are emitted

DeBroglie Wavelength

y = h/m*u where m = mass in KG not grams and u = speed in m/s and wavelength in m

Wave-particle duality

the concept that matter at the quantum level can exhibit both wave-like and particle-like properties, meaning that depending on the experimental conditions, a single entity can behave like a wave or a particle simultaneously

Heinsenberg’s Uncertainty Principle

it is impossible to know both the exact position and momentum of a particle simultaneously

Uncertainty of electron

Delta x = mdeltau greater than or equal h/4pi, m= MASS IN KG, u=uncertainty in speed/velocity, delta x= uncertainty in position

Quantum mechanics

Wave nature of objects on the atomic scale

Principal quantum number (n)

Level/shell of orbital (higher number is further away and higher energy level)

Angular momentum quantum number (l)

Sublevel/subshell of orbital, indicates shape, 0-n-1

L=0

S

L=1

P

L=2

D

L=3

F

Magnetic quantum number ml

Orientation of orbital, -L to 0 to +L

S orbital shape

Spherical

P orbital shape

Dumbbell

D orbital shape

Double dumbbell, clover

Total number of orbitals in a shell

n²

Maximum number of orbitals in a subshell

2 * L + 1

Spin quantum number ms

Magnetic field generated by electron, +1/2 or -1/2

For a given n value,

The higher the L value the higher the sublevel energy

Electron repulsions/ electron shielding

the phenomenon where inner shell electrons in an atom partially block the positive charge of the nucleus from the outer shell electrons, reducing the effective nuclear charge experienced by the outer electrons

An electron is attracted to the positive charge if the nucleus

Also known as Z nuclear charge

Higher nuclear charge lowers

Orbital energy, which stabilizes the atom by increasing electron attractions

Effective nuclear charge

Several electrons in same orbital repel a little and shield

Since p can hold 6 electrons while s can hold 2

More shielding will happen in p, so it is easier to remove an electron

Order of electron energy

S<P<D<F

Aufbau principle

Filling up orbitals with lowest energy

Hunds rule

One arrow in each first

As you go down a group

Atomic radius/size increases

As you go across a period

Atomic size/radius decreases and effective nuclear charge increases

Transition elements do not follow the pattern

• Small increase down a group from period 4 to 5 but none from 5 to 6

• Across a period, remain the same size since shielding counteracts increasing effective nuclear charge

As you go up a group

Ionization energy increases

As you go across a period (L to R)

Ionization energy increases

IE value greatly increases when

Removing a core (inner) electron

Electron affinity

Energy released when an electron is added to a neutral gaseous atom (negative number)

Second ea value is

An endothermic process

Metallic character

Acidity and Basicity

Removing an electron

Highest n value first then f,d,p,s

Adding an electron

Lowest n value with room then s,p,d,f

Isoelectric

Same number of electrons

Paramagnetic

Unpaired electrons & attracted by magnetic field

Diamagnetic

All of its electrons are paired & not affected by magnetic field

Ionic size/ radius

Cations (+) are smaller, anions (-) are bigger

For isoelectric ions,

The one with the most protons will be smallest