Pre-IB Chemistry 1: Harris Unit 6

The Photoelectric Effect

refers to the emission of electrons from metal when light shines on it

Frequency (v)

number of waves passing through a given point within a second (SI unit = Hz, waves per second)

Wavelength (λ)

the distance between corresponding points on adjacent waves

Electromagnetic Radiation

type of radiation behaving as waves

Quantum

minimum amount of energy able to be emitted or absorbed by an atom

Ground State

lowest energy state of an atom

Photon

particle of electromagnetic radiation without mass and containing a quantum of energy

Excited state

state in which an atom has a higher potential energy

Bohr Model of Hydrogen Atom

• electrons can only circle nucleus only in allowed paths called orbits

• energy of the electron is higher when the electron is in orbits that are successively farther from the nucleus

Louis de Broglie

• suggested that electrons be considered waves confined to the space around an atomic nucleus

Diffraction

bending of a wave as it passes by the edge of an object or through a small opening (electron wave can be diffracted)

Interference

when waves overlap (electron waves can interfere with each other)

Werner Heisenberg

proposed that any attempt to locate a specific electron with a photon knocks the electron off its course

Heisenberg uncertainty principle

it is impossible to determine simultaneously both the position and velocity of an electron or any other particle

Quantum theory

• foundation laid by Heisenberg uncertainty

  principle and the Schrödinger wave equation

• describes mathematically the wave properties of electrons and other very small particles

Atomic Orbital

three-dimensional region around the nucleus that indicates the probable location of an electron

principal quantum number (n)

indicates the main energy level occupied by the electron

angular momentum quantum number (l)

indicates the shape of the orbital

magnetic quantum number (m)

indicates the orientation of an orbital around the nucleus

spin quantum number (s/ms)

has only two possible values—(+1/2 , −1/2)—which indicate the two fundamental spin states of an electron in an orbital

Electron Configuration

arrangement of electrons in an atom

ground-state electron configuration

lowest-energy arrangement of the electrons for each element

Aufbau principle

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

Pauli exclusion principle

no two electrons in the same atom can have the same set of four quantum numbers

Hund’s rule

orbitals of equal energy 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 state

Orbital Notation

• An unoccupied orbital is represented by

  a line, with the orbital’s name written

  underneath the line.

• An orbital containing one electron is

  represented as one arrow with a line under it

• An orbital containing two electrons is represented as two arrows with a line under them

• The lines are labeled with the principal

  quantum number and sublevel letter

Electron-Configuration Notation

the number of electrons in a sublevel is shown by adding a superscript to the sublevel designation

highest-occupied energy level

electron-containing main energy level with the highest principal quantum number (inner shell electrons are not in this level)

Noble gas notation

• A noble-gas configuration refers to an outer main energy level occupied, in most cases, by eight electrons

• EX of this notation: Mg= [Ne] 3s²

Electron dot structure

amount of valence electrons

Finding valence electrons

all groups but transitional metals = group (only ones place) #

• except for He having only 2 valence electrons while being in Group 18, which would, in theory, actually = 8 valence electrons

Valence electron

outermost electrons

Electrons filling principal energy levels to the max

2n²

Electromagnetic spectrum wavelength values

• Gamma Rays: 10^-15 (on) to 10^-10

• X rays: 10^-10 to 10^-8

• Ultraviolet Light Rays: 10^-9  to 10^-7

• Visible Light Rays: 10^-7 to 10^-6

• Infrared Heat Waves: 10^-6 to 10^-4

• Microwaves: 10^-4 to 10^-1

• TV and FM Waves: 1 to 10^1

• AM Radio waves: 10^1.5 to 10^3

• Long radio waves: 10^3 to 10^5

Electromagnetic spectrum frequency values

• Gamma Rays: 10^25 (on) to 10^19.5

• X rays: 10^20 to 10^16

• Ultraviolet Light Rays: 10^17 to 10^15

• Visible Light Rays: 10^15

• Infrared Heat Waves: 10^15 to 10^11

Orientations possible for each sublevel

• s- 1

• p- 3

• d- 5

• f- 7

Sublevel designations

the different shapes and properties of electron orbitals within each energy level