Electron Configuration Chemistry I Mr. Pena

Bohr’s Atom Model -Confines electrons in shells -Electrons loses energy due to movement. -Electrons can be in certain levels depending of the energy they have. -The region where we can find the electron with high probability is called the orbital.

Nature of the electron -Thompson’s work show that e - behave like particles. -In 1924, Louis de Broglie states that e - behave like waves based on Bohr’s model. -This was explained in the electromagnetic spectrum.

The frequency is mathematicaly related to the wavelenght: c=λ ﹒ v Where c=speed of light (3.0 x 10 8 m/s) λ= wavelenght v= frequency Electromagnetic Spectrum

All the frequencies or wavelenghts of electric radiation.

Electromagnetic Spectrum -The movement of electrons produced light when received and release energy. -In 1905, Albert Einstein proposed that light have properties of light and waves.

Light Emission

Electron in lowest possible energy is in ground state. Electron that gains energy move to excited state. Electron release energy as go back to ground state.

Light Emission E 1 =Energy in ground state E 2 =Energy in excited stated. Overall energy= E 1 -E 2

Quantum Numbers -Number that specifies the properties of the electrons. -There are 4 quantum numbers: n,, m and m s

n= level number (n=1 thru 7). (n-1)= Shape and type of orbital s=0 p=1 d=2 f= 3 m (from –,0,+ )=Magnetic quantum number m s = Magnetic spin. Only have two possible numbers (+1/2 and -1/2) Quantum Numbers

Electron configurations -Arrangements of electrons in an atom. -Each orbital can have only 2 electrons and with different quantum numbers. This is known as Pauli exclusion principle.

Electron configuration Types and shapes of orbitals

Electron configuration Aufbau principle -Electron fill lowest energy levels first. Ex. 1s<2s<2p<3s<3p

Electron configuration Notations There are 3 notations: 1) Long notation or electron configuration 1s 2 2s 2 2p 6 2) Orbital Notation

Electron configuration 3) Shorthand Notation or Noble Gas configuration. [Ne]3s 2 3p 4

Electron configuration Hund’s Rule -For atoms in ground state, the number of unpaired electrons is the maximum possible and have the same spin.

Electron configuration Orbital Filling Order (Diagonal Rule)

Electron configuration Example What is the electron configuration of an element with atomic number of 9 (Z=9) An element with z=9 is Fluorine. We start with the less energy level and orbital, so then is 1s 2 2s 2 2p 5. The orbital notation will be then