\( \newcommand{\xrightleftharpoons}[2]{\overset{#1}{\underset{#2}{\rightleftharpoons}}} \) \( \newcommand{\conc}[1]{\left[\mathrm{#1}\right]} \) \( \newcommand{\chem}[1]{\mathrm{#1}} \) \( \definecolor{green}{RGB}{0,128,0} \) \( \definecolor{blue}{RGB}{0,0,255} \)

Lecture 7

Electron Structure of the Atom

Shaun Williams, PhD

Electromagnetic Radiation and Energy

White Light

  • Is composed of different colors that can be separated by a prism
    • Water acts as a prism for sunlight, giving the effect of a rainbow
  • Sources of white light
    • Sun
    • Regular (incandescent) light bulbs
A picture of rainbow and a prism seperating white light into a rainbow.

Electromagnetic Radiation

An image of electromagnetic spectrum running Gamma ray to x-ray, ultraviolet, visible, infrared, microwave, and finally to radio frequencies.

Differentiating the Kinds of Electromagnetic Radiation - Wavelength

An image of an electromagnetic wave with the wavelength marked as the distance peak-to-peak of the wave.

Differentiating the Kinds of Electromagnetic Radiation - Frequency

An image of electromagnetic spectrum running Gamma ray to x-ray, ultraviolet, visible, infrared, microwave, and finally to radio frequencies.

Frequency, Wavelength, and the Electromagnetic Spectrum

An image of electromagnetic spectrum running Gamma ray to x-ray, ultraviolet, visible, infrared, microwave, and finally to radio frequencies.

Duality of Light

\(\lambda\), \(\nu\), and \(\chem{E_{photon}}\)

\[ c=\lambda \nu \;\;\;\;\;\;\; \chem{E_{photon}}=h\nu \]

Energy is Quantized!

An image of a prism breaking white light up into a continuous sepctrum (rainbow) and a prism breaking up the light from various atoms in line spectra.

The Bohr Model of the Hydrogen Atom

  • Niels Bohr hypothesized that electrons orbit the nucleus just as the planets orbit the sun (planetary model) and have fixed radii.
  • He labeled the electron orbits with a number, starting with 1 closest to the nucleus and increasing as the orbits get further away from the nucleus.
    • This number is known as the Principal Quantum Number (\(n\)).
The rings where Bohr pictured electrons existing around the nucleus with n=1 nearest the nucleus and the n-value increasing outward.

Bohr Model and Light

The Bohr model the atom with arrowing showing electrons jumping from rings further away in towards rings nearer the nucleus and giving off light.

The Modern Model of the Atom

  • The modern model of the atom is based on Schrödinger's mathematical model of waves
  • This model describes electrons as occupying orbitals, not orbits.
    • Orbitals
      • Three dimensional regions in space where electrons are likely to be found, not a circular pathway
    • Principal energy level
      • Orbitals of similar size
Representations of the spherical electron cloud of an s-orbital in quantum mechanics.

Energy Levels

n=1 has the lowest energy. There is a large energy gap to n=2 and then every smaller energy gaps to the subsequent energy levels.

Orbitals

Representations of the spherical electron cloud of an s-orbital, the bar-bell shaped electron clouds of the p-orbital, the clover-shaped electron cloud of the d-orbitals, and the double clover-shaped electron cloud of the f-orbitals.

\(s\)-Orbitals

Graphics of the electron clouds of the 1s, 2s, and 3s showing that as the leading number increased, the size of the orbital increases.

\(p\)-Orbitals

Graphics of the electron clouds of the 2px, 2py, and 2pz showing that they each have the same bar-bell shape but lie on the difference Cartesian axes. Combining them all leads to something that looks vaguely spherical.

\(d\)-Orbitals

Graphics of the electron clouds of the dyz, dxz, and dxy showing that they each have the same 4-leaf clover shape but lie on the difference Cartesian planes.

Graphics of the electron clouds of the dx2-y2 and dz2 showing that they each have the same 4-leaf clover shape but lie on the difference Cartesian planes as all the other d-orbitals.

Orbital Diagrams

A graphic showing the boxes of the orbitals at this appropriate energy. From lowest energy, the order is 1s, 2s, 2p, 3s, 3p, 4s, 3d, 4p...

Orbital Diagrams Rules

Filling Orbitals Diagrams

An orbitals diagram showing two arrows for electrons (one up and one down) in the 1s box, two in the 2s box, and 1 arrow up in each of the first two boxes of the 2p. This is the orbital diagram of carbon.

Orbital Diagrams for the 1st Ten Elements

The orbital diagrams for the first ten elements.

Orbital Diagrams Rules

The orbital diagram and electron configuration of the carbon atom described in this slide.

Periodicity of Electron Configurations

The Principal Quantum Number and Sublevel on the Periodic Table

The periodic table with the elements removing showing that the first two column as the s-block, the right six columns are the p-block, the 10 transition metal columns are the d-block, and the 14 inner-transition metal columns are the f-block.

Valence Electrons for Main-Group Elements

More on Valence Electrons

Abbreviated Electron Configuration

Electron Configurations for Ions

Periodic Trends of Atoms

The reaction of the various alkali metals with water showing that the heavier the alkali metal, the more violent the reaction with water.

Ionization Energy

  • Ionization Energy
    • A measure of the energy required to remove a valence electron from a gaseous atom to form a gaseous ion.
    • In general, atoms with low ionization energies do not bind their electrons very tightly, and are therefore, very reactive.
    • The general trend for ionization energy is for ionization energy to increase from bottom to top and from left to right across the periodic table.
A version of the periodic table showing the various elements ionization energies. The ionization energies are increasing from bottom to top and from left to right.

Atomic Size

  • Atomic size is often described in terms of atomic radius.
    • Atomic radius is the distance from the center of the nucleus to the outer edge of the atom.
A graphic of the Cl2 molecule showing a distance of 199 pm from nucleus to nucleus and therefore the Cl atom has a diameter of 99.5 pm.

Trends in Atomic Size

A verson of the periodic table showing the various elements atomic radii. The radii decrease from bottom to top and from left to right.

Ionic Size

A graphic showing that the lithium atom decreased in size when it loses and electron. It also shows that the fluorine atom increases in size when it gains an electron.

Ionic Size

A graphic showing the trend in size for all the ions in an isoelectronic series. The largest are the most negative ions while the smallest are the most positive ions.

/