I. Key Terms and Phrases

nucleus the central region of an atom that contains most of its mass and all of its positive charge

line spectrum the discrete spectrum of the wavelengths of light given off by atoms

Bohr orbit the circular orbits of electrons around the nucleus of an atom in Bohr's model

atomic number the number of protons in the nucleus of an atom

ground state the case when the electrons in an atom are in their lowest possible energy levels

excited state the case when one or more electrons in an atom are in energy levels above the ground state

principal quantum number an integer value that determines the total energy of a state of hydrogen and sets the boundaries for the values of other quantum numbers

orbital angular momentum quantum number an integer value that determines the orbital angular momentum of an electron in an atom and sets the boundaries for the magnetic quantum number

magnetic quantum number a quantity of integer value that determines the possible values of a component of the orbital angular momentum of an electron in an atom

electron spin quantum number a value that determines the intrinsic angular momentum of an electron

state of an atom the specification of the quantum numbers for every electron in an atom

probability cloud the interpretation of matter waves for the electrons around the nucleus of an atom

shell electrons with the same principal quantum number are in the same shell

subshell specification of the orbital angular momentum quantum number

Pauli exclusion principle the principle that only one electron can occupy a given state in an atom

electronic configuration specification of n, , and the number of electrons in each subshell

periodic table a table of the elements that organizes them by their chemical properties

laser light amplification by the stimulated emission of radiation

II. Important Equations

Name/Topic	Equation	Explanation
Bohr's model		The radii of the Bohr orbits of single-electron atoms.
Bohr's model		The allowed energy levels of single-electron atoms in Bohr's model.
hydrogen spectrum		The wavelengths in the spectrum of hydrogen.
orbital angular momentum		The magnitude of the orbital angular momentum from the associated quantum number.
magnetic quantum number		The magnetic quantum number specifies one component of the orbital angular momentum.

III. Know Your Units

Quantity	Dimension	SI Unit
Rydberg constant (R)	[L-1]	m-1

IV. Tips

The radius of the smallest Bohr orbit, for n = 1, is called the Bohr radius; it is typically denoted as a₀ and has a value of

V. Additional Tools

Recording Calculator
This is a 'printing' scientific calculator. It allows you to check your calculations by reviewing your work.

Scientific Calculator
This is a standard scientific calculator.

Graphing Calculator
This is a simple graphing calculator, the JavaScript resource of the month for several months at Developer.com.

Physical Constants
This is a searchable database of physical constants.

Conversion Engine
This conversion factor tool gets almost 1000 hits a day and has been featured by Microsoft.

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