Unit 4 Electrons Chemistry Pre-AP

Electromagnetic Radiation

Radiation that exhibits wave-like behavior as it travels through space.

Visible Light

The very narrow part of the electromagnetic spectrum we can see.

Wavelength

On a wave, the distance between two crests or troughs. Symbol is λ (lambda).

Units of Wavelength

Distance measured in meters (m) or centimeters (cm).

Frequency

Number of wavelengths to pass a given point in one second. Symbol is f.

Units of Frequency

Measured in Hertz (Hz).

Amplitude

Wave's height from crest to origin or trough to origin.

Units of Amplitude

Displacement measured in meters (m) or centimeters (cm).

C (Speed of Light)

All forms of light travel at the same speed, 3.00 x 10^8 m/s

Wavelength and Frequency Relationship

Wavelength (λ) and frequency (f) are inversely related.

Photoelectric Effect

The emission of electrons from a metal when light shines on the metal.

Ultraviolet B

A type of ultraviolet radiation that has a wavelength of 3.24 x 10^-7 m.

Calculation of Frequency

C = λ x f, where C is the speed of light.

Calculation of Wavelength

Wavelength can be calculated using the formula λ = C / f.

Max Planck

German physicist who studied the emission of light by hot objects and contributed to the concept of quantum.

Inversely Related

As wavelength increases, frequency decreases, and vice versa.

Ultraviolet Radiation

Radiation from the sun that can burn the skin of most humans.

Intensity of Light

Wave theory predicted that light of any frequency could supply enough energy to eject an electron.

Quanta

the small distinct units

Planck-Einstein formula

E = h x f, where E is energy, h is Planck's constant, and f is the frequency of radiation.

Planck's constant

6.63 x 10-34 J-s.

Energy

directly proportional to frequency of light

Photon

A particle of electromagnetic energy having zero mass and carrying a quantum of energy.

Ground state

The lowest possible energy level of electrons in an atom.

Excited state

When electrons are at one or more quanta above their ground state.

Photon emission

When an electron loses energy to return to the ground state, a photon of light is emitted.

Atomic Emission Spectrum

A distinct color pattern unique to a substance, produced when passing electric current through a gas or vapor of a pure substance.

S Shape Orbital & # of Orbitals

Sphere, 1

P Shape Orbital & # of Orbitals

Dumbbell, 3

D Shape Orbital & # of Orbitals

Clover, 5

F Shape Orbital & # of Orbitals

Daisy, 7

Unique spectra

All elements emit light in unique, distinct patterns of visible light called atomic emission spectra.

Energy gap

The difference in energy between the excited state energy level and the ground state.

Calculation of energy

E = h x f, where E is energy, h is Planck's constant, and f is frequency.

h (planck's constant)

6.63 x 10^-34 Js

Light as a wave

Light can be bent and redirected or refracted.

Light behaves as both

a wave and a particle.

C

Speed of light, 3.00 x 10^8 m/s.

Electron Cloud: Quantum Model

The explanation for atomic emission spectra lead to an entirely new atomic theory.

Quantum Model

This breakthrough was significant because it predicted the location and properties of electrons in atoms with more than one electron.

Key attributes of the Atomic Quantum theory

Describes the wave-like properties of electrons and other small particles.

Heisenberg Uncertainty Principle

Heisenberg determined that it is impossible to determine simultaneously both the position and the velocity of an electron (or any other particle).

Wave functions

As a result of the Heisenberg Uncertainty Principle, the solutions to the Schrodinger equations called wave functions only give a probability of finding an electron at a given place around the nucleus.

Atomic orbitals

These regions are called atomic orbitals.

Quantum numbers

It takes four quantum numbers to completely describe the properties of atomic orbitals and the properties of the electrons in those orbitals.

Principal Quantum Numbers (n)

Identifies the main energy level of the orbital where the electron is located.

Primary energy levels

There are 7 possible primary energy levels to an atom.

Periods (rows)

Primary energy levels roughly correspond to periods on the periodic table.

Angular Momentum Quantum Number (l)

The angular momentum sublevel, symbolized by l, indicates the shape of the orbital.

Sublevels

orbitals of different shape within the same primary energy levels

Orbital Sublevels

correspond to a block on the periodic table.

Magnetic Quantum Number (m)

signifies the orientation of an atomic orbital around the nucleus.

Electrons in one orbital

holds 2 electrons.

Shape of orbitals

The shapes of orbitals are sphere, dumbbell, clover, and daisy.

Spin Quantum Number

The spin of an electron.

Electron Configuration

A way to express complete electron arrangement around an atom.

Ground-state configuration

These configurations are the ground-state configuration for each element.

Primary energy level

The large number in the electron configuration

Sublevel

The letter in the electron configuration that correspond to the section of the periodic table

Number of electrons in sublevel

The superscript in the electron configuration indicates the number of electrons in the sublevel.

Process to write electron configuration

Step 1: Determine total number of electrons in atom. Step 2: Identify the energy levels of the orbitals using the Periodic Table as a guide.

Aufbau Principle

An electron occupies the lowest energy level possible.

Maximum electrons in s sublevel

2

Maximum electrons in p sublevel

6

Maximum electrons in d sublevel

10

Maximum electrons in f sublevel

14

Noble Gas Configuration

A shorter way to write electron configuration in which a noble gas symbol substitutes for a portion of the configuration.

Orbital Notation

A graphical representation of electron configuration that illustrates all four quantum numbers for each electron.

Hund's Rule

Orbitals of the same sublevel are each occupied by one electron before any orbital is occupied by a second electron, and all electrons in singly occupied orbitals must have the same spin.

Pauli Exclusion Principle

No two electrons in an atom can have the same set of four quantum numbers.

Total of superscripts

Equals the atomic number in an atom.

Energy Level

The principal quantum number (n) that indicates the size and energy of an orbital.

Process to write orbital notation

Use horizontal lines to represent orbitals and arrows to represent electron spin.