Modern Atomic Theory
Modern Atomic Theory and The Periodic Table
A Brief History
n Atomic theory has changed over the past 2000 years:
– Early Greek Ideas:
– Dalton’s Model:
– Thomson’s Model:
– Rutherford’s Model:
Electromagnetic Radiation
n Basic wave characteristics:
– Wavelength ( )
– Frequency ( )
– Speed ( )
n Light is a form of ______.
n Light can also be considered to be composed of energy packets called ______, which behave like ______.
n Diagram:
The Bohr Atom
n Diagrams:
n German physicist Max Planck (1858 – 1947) observed the line spectrum of hydrogen and theorized that emitted energy is not a continuous stream but occurring in small discrete units called a ______.
n Danish physicist Niels Bohr (1885 – 1962) applied this concept to the single electron “orbiting” the nucleus in the hydrogen atom.
n The study of atomic spectra led Bohr to propose that:
– Electrons are found in ______in an atom.
– Spectral lines result from the radiation of quanta of energy when the electron ______.
n The lowest energy level is called ______.
n Any level above ground state is called an ______.
n The chemical properties of an element and its position on the periodic table depend on ______.
n Bohr’s ______for hydrogen does not work for any other element.
Quantum Theory
n In 1924, Louis de Broglie suggested that all matter has ______.
– Large objects have wave properties ______.
– Very small particles, ______, have observable wave properties.
n In 1926, Erwin Schrodinger created a mathematical model that described the wave behavior of the electron.
n This model can determine the ______of finding an electron in a certain region around the nucleus of the atom.
n This branch of physics is called ______.
n Electrons are found in ______-, a region in space around the nucleus where there is a high probability of finding an electron.
– When this mathematical orbital is visualized, the orbital looks like a
cloud (hence, the electron cloud).
n Modern atomic theory predicts the following:
n Electrons are found in discrete ______(n = 1, 2, 3…).
n Energy levels contain ______(s, p, d, f).
n Sublevels contain ______(s = 1, p = 3, d = 5, f = 7).
n Each orbital holds ______(s = 2e-, p = 6e-, d = 10e-, f = 14 e-)
n Electrons fill lowest energy sublevels first:
1s
2s 2p
3s 3p 3d
4s 4p 4d 4f
5s 5p 5d 5f
6s 6p 6d
7s 7p
Periodic Trends
Classification of Elements
n The Periodic Table Revisited.
– Russian chemist ______introduced the most successful arrangement of the elements to date in 1871.
– Vertical rows were arranged by ______.
– Horizontal rows were arranged by ______.
n ______arranged the first modern periodic table.
– This periodic table now contains information regarding the chemical symbol, atomic number, average atomic mass, physical state of each element, group’s numbers, electron configurations, as well as many other useful characteristics.
– Recently accepted names for elements 104-109 have been added.
– This periodic table is arranged mainly based on increasing ______.
n The modern periodic table is extremely useful in understanding and predicting properties of elements.
n Elements and Electron Configuration
– ______play the most significant role in determining the physical and chemical properties of an element.
– A relationship exists between the ______of the elements and their ______in the periodic table.
n Categories of elements.
– The noble gases.
• These are elements in which the outermost s and p sublevels are ______.
• These elements are also called the ______because they do not participate in many chemical reactions.
• Electron configurations:
n Categories of elements.
– The representative elements.
• In these elements, the outermost s or p sublevel is only partially filled.
• These are the ______elements.
• Electron configurations of the alkali metals:
• Electron configurations of the alkaline earth metals:
• Electron configurations of the halogens:
• The transition elements.
– These are the metallic elements in which the outermost s sublevel and nearby d sublevel contain electrons.
– These are the ______elements.
• The inner transition elements.
– These are the metallic elements in which the outermost s sublevel and nearby f sublevel generally contain electrons.
• Similarities within groups of elements.
– Alkali metals:
– Alkaline earth metals:
– Halogens:
– Noble gases:
• Summary statement:
Periodic Trends
• Trends in Atomic Size.
– The atomic radius is:
– The atomic radius of an element indicates its relative size.
• Group Trends:
• Periodic Trends:
• Trends in Ionization Energy.
– Ionization energy is:
• Group Trends:
• Periodic Trends:
• Trend in Ionic Size.
• Group Trends:
– Positive ions (cations) are always ______.
– Negative ions (anions) are always ______.
– Within a group:
• Period Trends:
• Trend in Electronegativity.
• Electronegativity is
• Group Trend:
• Periodic Trends:
• Range: 0.7 for Cesium to 4.0 for Fluorine.
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