Chemistry-an atom focused approach Ch. 3

electromagnetic radiation

forms of energy

electromagnetic spectrum

range of the frequencies of electromagnetic radiation

Maxwell's theory of the properties of light

radiation can travel through space (or a transparent medium) on two perpendicular axes: the magnetic field and electric field

Wavelength (λ)

the distance between two wave crests

Frequency (∨)

the number of crests that pass by a stationary point per second

all forms of radiation

travel at the speed of light (c), 2.998 * 10⁸ m/s

the relationship between wavelength and frequency is

inverse, λ = c/v

atomic emission spectra

element spectra, each element emits a characteristic spectrum

atomic absorption spectra

narrow dark lines on a continuous spectrum. Dark lines are in the same position as the emission spectra colored lines

Blackbody radiators

something that perplexed physicist because of its ability to absorb all light at cold temperatures, as well as emitting radiation dependent on temperature alone (i.e. temp = frequency)

no radiant energy

is truly continuous

objects only emit electromagnetic radiation

in integral multiples of an elementary unit, called a quantum

energy =

hv
h= planck's constant 6.626 * 10 ^-34 j•s
v = frequency
relating energy of a quantum to the energy of a wavelength

Quantized

having values of a whole number of a base value

quantum theory

energy is released or absorbed in discrete packets, or quantums, of energy

photon

tiny packets of radiant energy

photoelectric effect

electrons are emitted by metals or semi conductor materials when illuminated by or absorb electromagnetic radiation

incident radiation

radiation acting on something

threshold frequency (v₀)

minimum frequency at which photoelectrons are emitted

photoelectrons

electrons released by light

work function (φ)

in regard to material, the minimum quantity of energy required to emit photoelectrons from a photoelectric material

work function (φ) =

hv₀, work function value measures the force of attraction between an atoms nuclei and the electrons surrounding it

the higher the frequency above the work function threshold

the greater the kinetic energy of the ejected electron

work function (φ) of target metal

hv- KE electron

Different electron "falls"

produce different wavelengths (when electrons are excited, they jump to a higher energy state. The fall is when they fall back to their ground state)

larger electron transitions

release greater amounts of energy

empirical equation

equation derived solely from experiments w/o a theory backing it

Balmer equation for 4 brightest hydrogen emissions

λ (nm) = (364.56m^2/ m^2 - n^2) where n=2 and m>2

The Rydberg equation

gave a more general empirical formula where n₁ doesn't have to = 2, which allowed scientist to predict other series of hydrogen emission lines
the equation is 1/λ = Rh (1.097 * 10 ^-2 nm) (1/n₁² -1/n₂²) where n₂ > n₁

wavenumber

the inverse of the wavelength, directly proportional to the energy of an electron

In the Rydberg equation, the n₁ and n₂ correspond to

energy levels inside a hydrogen atom. the energy an atom emits or absorbs is the same as the difference in energy between a pair of energy levels

The Bohr Model

Electrons revolve around the nucleus of an atom at available, discrete orbitals
Orbits represent discrete energy levels in the atom
assigned orbits go from n=1, with larger orbital values being higher (less electron) energy

Can find energy in an electron using:

-2.187 * 10 ^-18 J (1/n^2), as n approaches ∞ E approaches 0

Zero energy

it means that the electron approaching n=∞ no longer exists as a part of the hydrogen atom. The hydrogen atom now exists as two separate particles: the H+ ion and the free electron

Energy equation has negative constant

because we want to measure the additional energy input help to help pry a negative electron from its positively charged nucleus

Bohr's model provides

theoretical framework to explain past scientists, only good for atoms or ions with one electron stably orbiting the nucleus

An electron moving through two different energy levels

ninitial = the initial electron energy state
nfinal = the final energy state
∆E = -2.78 * 10 ^-18 (1/nfinal² - 1/ninitial²)
When electron moves farther from nucleus 1/nfinal < 1/ninitial, therefore, it is a negative times a negative, making the overall equation positive, representing an increase in energy level
1/nfinal > 1/ninitial, indicates a decrease in energy level, showing an electron moving from a higher orbital level to a lower one

Ground state

when electron is at lowest energy level
ex. Hydrogen at n = 1, can't get to a lower orbital

Excited State

when electron is at higher energy level
ex. Hydrogen electron in orbital > n=1

Electron absorbing a quantum of energy

jumps to a higher energy level, matching energy difference of states

Electron emitting a quantum of energy

falls to a lower energy level, matching energy difference of states

Electron transition

movement of electrons to any two different energy levels

ionization

absorption of enough energy to separate the electron from the atom

De Broglie observations

electrons can act as particles of matter as well as wave
wavelength is inversely proportional to energy

de Broglie equation for calculating waves in motion

λ = h/mu
where h = planck length (6.626 *10-³⁴ J s)
m = mass (kg)
u = speed (m/s)
product of mass and speed is the particle's momentum

more momentum

shorter wavelength

matter wave

particle with wave like properties, explain stability of electron levels

de Broglie said orbiting electrons behave

like circular waves oscillating around the electron

Stable pattern of circular waves only

achieved if the circumference is a whole number multiple of wavelength

Orbit circumference

nλ,
n = the number of matter wave wavelength in orbit's circumference

Erwin Schrodinger

Developed the Schrodinger wave equation to describe the behavior of matter waves and the atomic model of hydrogen

Schrodinger wave equation

the solutions to the equations are called wave functions

Wave Functions- φ

describes how matter waves of an electron in an atom vary in the size and location inside the atom

orbitals (φ)

clarified by max born, space within the atoms where the probability of finding an electron is higher,
Have distinctive shapes, orientations, and average distances from the nucleus,
helpful in calculating the probability of electron transitions between orbitals when absorbing or emitting quantum of energy

quantum numbers

unique combination of 3 numbers, all of which are solutions to the schrodinger equation

n, principle quantum number

a positive integer that represents a relative size or energy of an orbital or group of orbitals,
orbitals with the same n value are in the same shell