Isotope Formulae, Electron

Configurations & Orbital Diagrams

Isotope Formulae•Provide element’s symbol•Mass number

–mass# = #p+ + #n–written as a superscript to the left

•Atomic number–atomic# = #p+ or #e-

–written as a subscript to the left

Isotope Formulae

XMass#Atomic#

C126

Carbon has two naturally occurring isotopes:carbon-12 and carbon-13

C136

Isotope FormulaeGive the isotope formula for each of thefollowing:

H311. Hydrogen with 2 neutrons

2. Fluorine with 9 neutrons

3. Uranium with 143 neutrons

F189

U23592

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

1s1

energy level

sublevel/orbital

# of electrons

Electron Configurations

•Write the e- configurations of the next 9 elements (through Ne).

1s2He…1s22s1

Li…1s22s2

Be…1s22s22p1

B…

Look at the sumof the superscripts…

Electron Configurations1s22s22p2C…1s22s22p3N…1s22s22p4O…1s22s22p5

F…1s22s22p6

Ne…

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

1s2He…[He]2s1Li…[He]2s2Be…[He]2s22p1B…[He]2s22p2

C…

Electron Configurations…shorthand

[He]2s22p3

N…[He]

2s22p4O…

[He] 2s22p5F…[He] 2s22p6Ne…

Electron Configurations…shorthand

[Ne]3s1Na…[Ne]

3s23p2Si…

[Ne] 3s23p5Cl…[Ne] 3s23p6Ar…

Electron Configurations…shorthand

[Ar]4s2Ca…[Ar] 4s23d1Sc…[Ar] 4s23d5Mn…[Ar]

4s23d104p4Se…

Electron Configurations…shorthand

[Kr] 5s24d105p5I…[Xe] 6s25d1La…[Xe] 6s25d14f1Ce…[Xe] 6s24f145d10Hg…

Exceptional Electron Configurations…

shorthand[Ar]

4s23d4Cr…

[Ar] 4s23d9Cu…[Kr]

5s24d4Mo…

[Kr] 5s24d9Ag…

[Ar]

4s13d5[Ar]

4s13d10[Kr]

5s14d5[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)

E

1s

2s

2px 2py 2pz

3px 3py 3pz

3s

Orbital Diagram for H

E

1s

2s

2px 2py 2pz

3px 3py 3pz

3s

Orbital Diagram for He

E

1s

2s

2px 2py 2pz

3px 3py 3pz

3s

Orbital Diagram for Be

E

1s

2s

2px 2py 2pz

3px 3py 3pz

3s

Orbital Diagram for C

E

1s

2s

2px 2py 2pz

3px 3py 3pz

3s

Orbital Diagram for O

E

1s

2s

2px 2py 2pz

3px 3py 3pz

3s

Orbital Diagram for P

E

1s

2s

2px 2py 2pz

3px 3py 3pz

3s

Wrap-Up•Write the electron

configuration for nitrogen.•Write the orbital diagram for

nitrogen.