Chemistry Chapter 4 Arrangement of Electrons in Atoms electromagnetic radiation- a form of energy that exhibits wavelike behavior as it travel through space wavelength ( λ )- the distance between corresponding points on adjacent waves frequency ( f ) the number of waves that pass through a specific point in a specific time hertz ( Hz )- a frequency of one wave per second

Speed of Electromagnetic Radiation The speed ( c ) of all wavelengths of electromagnetic radiation = 3.0 x 108 m/s. c = fλ IF “c” is a constant, then wavelength varies inversely with the frequency of electromagnetic radiation.

Photoelectric Effect photoelectric effect- the emission of electrons from a metal when light shines on that metal quantum- the minimum amount of energy that can be gained or lost by an atom photon- a quantum of light energy ground state- the lowest energy state of an atom excited state- a higher energy state

Spectra line-emission spectrum- The specific colors (frequencies) of light emitted when an atom returns to the ground state from the excited state. It can be seen when the light is separated by a prism and will give an element a specific spectrum. continuous spectrum- the emission of a continuous range of frequencies of electromagnetic radiation

Section 2 The Quantum Model of the Atom Heisenberg Uncertainty Principle- it is impossible to determine simultaneously both the position and the velocity of an electron Quantum theory- describes mathematically the wave properties of electrons orbital- a three-dimensional region around the nucleus that indicates the probable location of an electron Each orbital can contain a maximum of 2 electrons.

Atomic Orbitals and Quantum Numbers quantum numbers- specify the properties of atomic orbitals and the properties of the electrons in the orbitals principal quantum number- indicates the main energy level occupied by an electron the number of electrons possible per energy level = 2 n2 where n = energy level angular momentum quantum number- indicates the shape of an orbital s, p, d, & f magnetic quantum number- indicates the orientation of an orbital around the nucleus of an atom spin quantum number- indicates the two fundamental states of spin of an electron

Orbitals There is a single “s” orbital per energy level for a maximum of 2 “s” electrons per level. the energy level for “s” orbitals = the period number There are 3 “p” orbitals per energy level for a maximum of 6 “p” electrons per level. the energy level for “p” orbitals = the period number There are 5 “d” orbitals per energy level for a maximum of 10 “d” electrons per level. the energy level for “d” orbitals is the period number minus 1 There are 7 “f” orbitals per energy level for a maximum of 14 “f” electrons per level. the energy level for “f” orbitals is the period number minus 2

Section 3 Electron Configurations electron configuration- the arrangement of electrons in an atom Rules governing electron configuration: 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 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

Electron Configuration Notation ORBITAL NOTATION: See pg 112-113. ELECTRON-CONFIGURATION NOTATION: See pg 113 [Ne] 3s23p4 Do Practice #1 & #2 on page 113.

Elements & Electron Configurations 1st period elements- see periodic table 2nd period elements 3rd period elements noble-gas configuration- refers to an outer main energy level occupied by eight electrons ( ns2np6 in most cases) 4th period elements 5th period elements Do Practice #1-4 on page 121.

Elements & Electron Configurations Elements of the 6th and 7th periods contain “f” orbitals. Do Practice #1 & 2 on page 122. Do Section Review #5 on page 122. Do Chapter review #33, 36, & 38 on pages 125-126. Review for Chapter 4 Test

Chapter 4 Test- (40 questions) Know the meaning of the formula c = fλ . Know the meaning of hertz, wavelength, photon, photoelectric effect, ground state, excited state. Know how EMR travels through space. Know how a line spectrum is produced. Know what must happen for an electron to move between the ground and excited states. Understand the Bohr model of atoms. Know the definition of electron cloud, the quantum numbers, orbital. Know how to calculate number of electrons per energy level.

Chapter 4 Test Understand the differences in the energies of different orbital sublevels. Know Aufbau principle, Hund’s rule, & Pauli exclusion principle. Identify elements using their electron configuration notation. Determine the electron configuration notation of elements. Know the definition of a noble gas. Write an electron configuration notation using an element’s orbital notation. Identify an element using its orbital notation diagram.