Chapter 4 Arrangement of Electrons in Atoms

4-1 The Development of the New Atomic Model Rutherford’s atomic model – nucleus surrounded by fast- moving electrons- not complete model

Electromagnetic Radiation- form of energy that exhibits wavelike behavior Ex: visible light, microwaves, x-rays Wave Nature of Light

Electromagnetic Spectrum- encompasses all forms of EM radiation

Electromagnetic Spectrum

Wavelength ( λ ) - shortest distance between equivalent points on a continuous wave Measured crest to crest or trough to trough

Frequency ( ν ) - number of waves that pass a given point per second 1 Hertz (Hz) = 1 wave per second; SI unit of frequency

Amplitude- wave’s height from the origin to a crest or from origin to trough Speed of light = wavelength x frequency C = λν

Photoelectric Effect- electrons are emitted from a metal’s surface when light of a certain frequency shines on the surface Ex: calculator with photoelectric cell

Particle Nature of Light Quantum concept- produces glowing light of hot objects Quantum- minimum amount of energy that can be gained or lost by an atom

E quantum = hv E = energy V = frequency h = Planck’s constant; x Js J is joule; SI unit for energy

Photon- particle of EM radiation with no mass that carries a quantum of energy E photon = hv

Ground State- lowest allowable energy state of an atom Excited State- when an atom gains energy

Line Emission Spectrum- set of frequencies of the EM waves emitted by atoms of the element Unique to each element, used for identification Continuous spectrum

Bohr Model of the Atom- proposed that hydrogen atom has only certain allowable energy states

Sect. 4-2: The Quantum Model of the Atom Electrons as waves…De Broglie applies light’s wave-particle duality to electrons/Bohr’s model

Heisenberg Uncertainty Principle – impossible to know position and velocity at same time Schrödinger wave equation

Quantum theory – describes mathematically the wave properties of electrons Orbital – probable location of electron around nucleus

Atomic Orbitals and Quantum numbers Quantum numbers – specify properties of atomic orbitals and electrons in orbitals solutions to Schrödinger wave equation

Principal quantum number (n) – represents main energy level (shell) & tells how many sublevels Positive integers (1,2,3,etc.) Total # orbitals per shell = n 2 Total # electrons per shell =2n 2

Angular momentum quantum number (l) – indicates shape of orbital (sublevel) l = zero and all positive integers less than or equal to n-1 l=0, s orbital (spherical) l=1, p orbital (dumbbell) l=2, d orbital l=3, f orbital

Magnetic quantum number (m) – indicates the orientation of orbital around nucleus range from -2 to +2, depending on sublevels

Spin Quantum number – indicates spin state of electron can only equal ½ or -½ orbital holds 2 max electrons & they must have opposite spins

Sect. 4-3: Electron Configurations Electron configuration – arrangement of electrons in an atom

Rules for Electron Configurations Aufbau principle – lowest energy level fills first Pauli exclusion principle – electrons in same orbital, opposite spin Hund’s rule – orbitals of equal energy must all have 1 electrons before a second can be added

Orbital Notation (Diagram) – lines, arrows, principal quantum #, and sublevel letter Electron Configuration Notation – principal quantum #, sublevel letter, and superscript (# e-) Noble Gas Notation – shortened version of electron configuration notation

Deviations from normal electron configurations (more stable with pulling one from s to half- fill or fill d) Chromium Copper