Electronic Structure

• Electronic structure: the arrangement and energy of electrons.

Waves

• Electromagnetic radiation moves as waves through space at the speed of light.

• Wavelength ($\lambda$): the distance between corresponding points on adjacent waves.

• Frequency ($v$): the number of waves passing a given point per unit of time.

• The longer the wavelength, the smaller the frequency. Example:

  • Top wave = low frequency, long wavelength

  • Bottom wave = high frequency, short wavelength

Electromagnetic Radiation

• All electromagnetic radiation travels at the same velocity.

• The speed of light $(\:c\:)$ is $3.00\times 10^{8}$ $m/s$

  • $c=\lambda v$

  • $3.00\times 10^{8}$ $m/s$ = (wavelength)(frequency)

The Photoelectric Effect

• Energy is proportional to frequency

  • $E=hv$

  • Plank’s constant ($h$) is $6.626\times 10^{-34}$ $J\sdot s$

Electron Configuration

• Describes where electrons are located around the nucleus of an atom.

• Moves diagonally

• 1s² → 2s² → 2p⁶ → 3s² → 3p⁶ → 4s² → 3d¹⁰ → 4p⁶ → 5s² → 4d¹⁰ → and so on

Electron Configuration Examples

• H: 1s¹

  • Has 1 total electron

• He: 1s²

  • Has 2 total electrons

• Li: 1s²2s¹

  • Has 3 total electrons

• Be: 1s²2s²

  • Has 4 total electrons

• B: 1s²2s²2p¹

  • Has 5 total electrons

• C: 1s²2s²2p²

  • Has 6 total electrons

• N: 1s²2s²2p³

  • Has 7 total electrons

• O: 1s²2s²2p⁴

  • Has 8 total electrons

• F: 1s²2s²2p⁵

  • Has 9 total electrons

• Ne: 1s²2s²2p⁶

  • Has 10 total electrons

Row and Energy Levels

• The periodic table is broken up into four blocks: s, p, d, and f.

  • Columns 1-2 and He are a part of the s block

  • The transition metals (columns 3-12) are the d block

  • Columns 13-18 make up the p block

  • The lower elements are part of the f block

• The row indicates the highest occupied electron level.

• The columns gives the outermost electron configuration (the superscript)

Quantum Mechanics

• Quantum mechanics: describes the movement of electrons.

Quantum Numbers

• Orbitals: describes a spatial distribution of electron density.

• An orbital is described by a set of four quantum numbers.

Principal Quantum Number (n)

• The principle quantum number, n, describes the energy level on which the orbital resides.

• The values of n are integers greater or equal to 1.

  • n = 1, 2, 3, … $\infty$ $\geq 1$

• These correspond to the values in the Bohr model.

Angular Momentum Quantum Numbers (l)

• This quantum number defines the shape of the orbital.

• Allowed values of l are integers ranging from 0 to n-1

• Letter designate the different values of l. This defines the shape of the orbitals.

  Value of l	Letter used
  0	s
  1	p
  2	d
  3	f

Magnetic Quantum Number (m_l)

• The magnetic quantum numbers described the three-dimensional orientation of the orbital.

• Allowed values of m_l are integers ranging from -l to l including 0.

  • $-l\leq m_{l}\leq l$

• There can be up to 1 s orbital, 3 p orbitals, 5 d orbitals, and 7 f orbitals.

• Orbitals with the same value of n form an electron shell.

• Different orbitals types within a shell are subshells.

Summary

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Orbitals

s Orbitals

• The values of $l$ for s orbitals is 0

• Spherical in shape

• Radius of the sphere increases with the value of n

p Orbitals

d Orbitals

f Orbitals

Spin Quantum Number, m_s

Orbital Diagrams