Chemistry Chapter 5

What did Bohr propose and his model of the atom?

Bohr Proposed that an electron is found Only in specific circular paths, or orbits, around the nucleus

Energy level

The fixed energies an electron can have

Energy levels

1.An electron can move from one energy level to another
2.The electrons in an atom can't exist between energy levels
3. To move from 1 energy level to another, an � must gain or lose just the right amount of energy

Quantum

The amount of energy required to move an electron from one energy level to another energy level

The energy of an electron is...

Quantized

Electron energy

1.The amount of energy an � gains or loses in an atom is not always the same
2. Higher energy levels are closer together
3. The higher the energy level occupied by the � the less energy it takes the � to move from that energy level to the next higher ener

Problem with Bohrs model

It failed to explain the energy absorbed and emitted by atoms with more than one �

What does the quantum mechanical model determine about the electrons in an atom?

The quantum mechanical model determines the allowed energies and electron can have and how likely it is to find the � in various locations around the nucleus of an atom

Quantum mechanical model

The modern description of the electrons in atoms. came from the mathematical solutions to the Schr�dinger equation

How do sublevels of principal energy levels differ?

Each energy sublevel corresponds to one or more orbitals of different shapes. The orbitals describe where an electron is likely to be found

Atomic orbital

For each energy level, the Schr�dinger equation also leads to a mathematical expression. Describing the probability of finding an electron at various locations around the nucleus

What are the three rules for writing the electronic configurations of elements?

Three rules- the aufbau principle, the Pauli exclusion principle, & Hunds rule tell you how to find the � configuration of atoms.

Cr � configuration
Cu � configuration(exceptions to rule)

Cr- 1s2, 2s2, 2p6, 3s2, 3p6,3d5, 4s1
Cu-1s2, 2s2, 2p6, 3s2, 3p6, 3d10, 4s1

What causes atomic emission spectra?

When atoms absorbs energy, their � move to higher energy levels. These electrons lose energy by emitting light when they return to lower energy levels

Amplitude

Maximum displacement between the crest and the middle

Wavelength

Distance between two crest or successive pieces. Measured in meters or nanometers

Frequency

Number of waves per second. Measured and hertz(Hz)

Speed-C

Speed =Wavelength x frequency ( indirectly related)

Spectrum

When sunlight passes through a prism, the different wavelengths separate into a spectrum of colors

How did Einstein explain the photonelectric effect?

To explain the photonelectric effect, Einstein proposed that light could be described as quanta of energy that behave as if they were particles. Can be called photons

Photonelectric effect

� are rejected when light shines on a metal. � only eject if the metal & wavelength are right

Lights nature

It has a dual nature. Acts as particles and waves

How are the frequencies of light emitted by an atom related to changes of electron energies?

The light emitted by an electron moving from a higher to a lower energy level has a frequency directly proportional to the energy change of the electron

How does quantum mechanics differ from classical mechanics?

Classical mechanics adequately describe the motions of bodies much larger than atoms, while quantum mechanics describes the motions of subatomic particles and atoms as waves

Revising the atomic model

1.Bohr proposed that an electron is found only in specific circular path, or orbits, around the nucleus.
2.The quantum mechanical model determines the allowed energies and electron can have and how likely it is to find the electron in various locations ar

Electron arrangement in atoms

Three rules- The aufbau principal, the pauli exclusion principle and the hunds rule-tell you how to find the electron configuration of atoms

Atomic emission spectra and the quantum mechanical model

1. When atoms absorb energy, their � move to higher energy levels. These electrons lose energy by emitting light when they return to lever energy levels.
2. To explain the photoelectric effect, Einstein proposed that light could be described as quanta of

Bohr

Believed that if the electrons stayed in the lowest possible orbit, ground state, atom was stable
If the atom absorbed energy, it could move to an outer energy level which he referred to as the excited state.( unstable)

Quantum mechanical model(Charged cloud model)

Shows where the highest probability at any given moment of finding an electron. This region is called an electron cloud and represented by a probability plot

Max born

Used Schr�dinger's equation to calculate the probability of finding an electron

Quantum numbers

1. Principle quantum numbers(n)- energy levels(1-7)
2. 2nd quantum number(l)- sublevel (# of sublevels=n)
3. 3rd quantum number(m)- orbital
4. 4th quantum number(s)- spin of �( � will spin in different cycles)

Orbital

Region of space that can occupied by a maximum of 2 electrons

s p d f

S=Spherical shaped, p= dumbbell shaped. All ground level

g h i

Excited state level

Number of orbitals

S-1 orbital, P-3 orbital, D-5 orbitals, F-7 orbitals, G-9 orbitals, H-11 orbitals

Pauli exclusion principle

No two electrons can have the same set of #4 quantum numbers(all others can be the same)

Aufbau principle

Electrons occupy orbitals with the lowest energy first

Hunds rule

When electrons occupy orbitals of equal energy(same sublevel) one electron enters each orbital, all with parallel spins, until there is one electron and each and then they pair up

Orbital diagrams

S=1 box, p=3 boxes, d=5 boxes, f=7 boxes

Short cut for orbital diagram

Always use the closest Nobel gas( in brackets) then count the rest as normal

Nobel gases

Are all stable- octane shells( s&p full)

Valence shell

Outermost energy level(highest)

Valence electrons

Electrons located in the outermost shell. 8� max

Electromagnetic radiation

Radiant energy

Types of electromagnetic radiation

Radio,Rada, Microwaves, Infrared, Visible, UV, X-rays, GammaRay's( Flows from lowest to highest)

Visible radiation

It's a combination of electric and magnetic fields, results in a regular repeating pattern

Visible radiation types

Red, orange, yellow, green, blue, indigo, violet(ROYGBIV)

Characteristics of waves

1.wavelength(m,nm)
2. Frequency(Hz)
3. Speed(m/s)
4. Amplitude

Atomic emission spectrum

Energy emitted from an atom that produces spectral lines

Absorption spectrum

Energy absorbed by an atom when exposed to always links of light- missing lines

Visible spectrum

Has wavelengths between 400 and 700 nm
1 m equals 1�10 to the ninth nanometers

Bohr explained the hydrogen spectrum by?

Using ideas from the quantum theory developed by Max Planck

Quantum theory

Energy is given often in packets called Quanta or photons

Max Planck

1.Stated that energy given off is directly related to the frequency
2. He created the Planck's constant(e=h x frequency)

Planks ideas

His ideas were used to explain why electrons were in energy levels with a definite amount of energy. And to move levels a specific amount of energy had to be absorbed or emitted.
Since those ideas we have found in addition to energy levels there sublevels

Sublevels and orbitals

Help explain the additional spectral lines in atoms other than hydrogen

Ground state

When electrons occupy the lowest possible energy levels(Stable atoms)

Excited state

Electrons are in higher energy levels because they have absorbed energy(Unstable atom)

Electron transition

Electrons go back to the ground state and when they become stable they give off energy and light is given off

Light energy

Planck stated that light energy has a wave that had particle like characteristics

deBroglie

He reasoned that if Planck was correct maybe a particle can have wavelike characteristics

Wave-particle duality of nature

And nature things can have both wave and particle properties examples are light and electrons

Newtonian Classical mechanics

Refers to visible objects at ordinary velocities

Quantum mechanics

Refers to very small objects with velocities at or near the speed of light

Heisenberg uncertainty Principal

It is impossible to know the precise location and velocity of a subatomic particle at the same time. To determine the location you have to interact with it and that changes the velocity

Schr�dinger's work

Investigated the wavelike character of electrons; and he developed equations to describe their wave behavior

Emitting

Is when you go from a higher level of energy to a lower

Absorbing

Is when you go to a higher level of energy from a lower level