# Isotope Formulae, Electron Configurations & Orbital Diagrams

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Isotope Formulae, Electron Configurations & Orbital Diagrams

Isotope Formulae Provide element’s symbol Mass number Atomic number
mass# = #p+ + #n written as a superscript to the left Atomic number atomic# = #p+ or #e- written as a subscript to the left

X C C Isotope Formulae Mass# Atomic# 12 6 13 6
Carbon has two naturally occurring isotopes: carbon-12 and carbon-13 C 12 6 C 13 6

Isotope Formulae Give the isotope formula for each of the following: H 3 1 1. Hydrogen with 2 neutrons F 18 9 2. Fluorine with 9 neutrons U 235 92 3. Uranium with 143 neutrons

Valence Electron(s) The electron(s) farthest from the nucleus or in the outermost energy level.

Aufbau Principle Comes from German word meaning “to build”
Electrons will occupy lower energy orbitals first

Pauli Exclusion Principle
An atomic orbital can hold at most two electrons. If an atomic orbital holds two electrons, they must have opposite spins.

Hund’s Rule When filling atomic orbitals of equal energy, place electrons with parallel spins in the orbitals first. Then, place the oppositely spinning electrons in to the orbitals.

Electron Configurations
Also describe where electrons live within an atom It’s like a translation of quantum numbers. They give the energy level, atomic orbital, and number of electrons residing in the orbital and energy level.

Electron Configurations
Energy level May be any positive integer Just like the principal quantum number

Electron Configurations
Atomic Orbital or Sublevel Represented by letters: s, p, d, f Translates azimuthal number and magnetic number s is the same as l = 0 p is the same as l = 1 d is the same as l = 2 f is the same as l = 3

Electron Configurations
Number of Electrons in either an atomic orbital or a sublevel max of 2 in the s sublevel max of 6 in the p sublevel max of 10 in the d sublevel max of 14 in the f sublevel

Electron Configurations
Use the periodic table to guide you in writing electron configurations. Find the link between 2,6,10, and 14 and the periodic table.

Electron Configurations
Hydrogen energy level 1s1 # of electrons sublevel/orbital

Electron Configurations
Write the e- configurations of the next 9 elements (through Ne). He… 1s2 Li… 1s22s1 Look at the sum of the superscripts… Be… 1s22s2 B… 1s22s22p1

Electron Configurations
1s22s22p2 N… 1s22s22p3 O… 1s22s22p4 F… 1s22s22p5 Ne… 1s22s22p6

Electron Configurations
Shorthand configurations are written by assuming that you can let the symbol of the noble gas preceding the valence electrons represent the e- configuration to that point.

Electron Configurations …shorthand
He… 1s2 Li… [He]2s1 Be… [He]2s2 B… [He]2s22p1 C… [He]2s22p2

Electron Configurations …shorthand
[He]2s22p3 O… [He] 2s22p4 F… [He] 2s22p5 Ne… [He] 2s22p6

Electron Configurations …shorthand
Na… [Ne]3s1 Si… [Ne] 3s23p2 Cl… [Ne] 3s23p5 Ar… [Ne] 3s23p6

Electron Configurations …shorthand
Ca… [Ar]4s2 Sc… [Ar] 4s23d1 Mn… [Ar] 4s23d5 Se… [Ar] 4s23d104p4

Electron Configurations …shorthand
[Kr] 5s24d105p5 La… [Xe] 6s25d1 Ce… [Xe] 6s25d14f1 Hg… [Xe] 6s24f145d10

Exceptional Electron Configurations…shorthand
Cr… [Ar] 4s23d4 [Ar] 4s13d5 Cu… [Ar] 4s23d9 [Ar] 4s13d10 Mo… [Kr] 5s24d4 [Kr] 5s14d5 Ag… [Kr] 5s24d9 [Kr] 5s14d10

Orbital Diagrams Show the electron configuration while illustrating the Aufbau Principle, Pauli Exclusion Principle, and Hund’s Rule Place energy on the y-axis Use lines to represent orbitals Use up and down arrows to indicate spin

Orbital Diagrams (template)
3px 3py 3pz 3s E 2px 2py 2pz 2s 1s

Orbital Diagram for H 3px 3py 3pz 3s E 2px 2py 2pz 2s 1s

Orbital Diagram for He 3px 3py 3pz 3s E 2px 2py 2pz 2s 1s

Orbital Diagram for Be 3px 3py 3pz 3s E 2px 2py 2pz 2s 1s

Orbital Diagram for C 3px 3py 3pz 3s E 2px 2py 2pz 2s 1s

Orbital Diagram for O 3px 3py 3pz 3s E 2px 2py 2pz 2s 1s

Orbital Diagram for P 3px 3py 3pz 3s E 2px 2py 2pz 2s 1s

Wrap-Up Write the electron configuration for nitrogen.
Write the orbital diagram for nitrogen.

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