Presentation on theme: "Chapter 5 The Periodic Law Modern Russian Table."— Presentation transcript:
Chapter 5 The Periodic Law
Modern Russian Table
Chinese Periodic Table
Orbital Filling Table
Periodic Table with Group Names
Chapter 5 The Periodic Law 5.1 History of the Periodic Table
Predecessors to the Modern Periodic Table Dobereiner’s Triads J.W. Dobereiner classified some elements into groups of three, which he called triads. similar chemical propertiessimilar chemical properties physical properties varied in an orderly way according to their atomic masses.physical properties varied in an orderly way according to their atomic masses.
Mendeleev’s Periodic Table Dmitri Mendeleev
Predecessors to the Modern Periodic Table Mendeleev’s Periodic Table repeated in an orderly way increasing atomic mass Dmitri Mendeleev realized that the chemical and physical properties of the elements repeated in an orderly way when he organized the elements according to increasing atomic mass. In 1869, Mendeleev published a table of the elements organized by increasing atomic mass. Mendeleev was a Russian scientist and is often referred to as the “Father” of the Periodic Table. PeriodicityPeriodicity is the tendency to recur at regular intervals.
Mendeleev’s Table Mendeleev’s Table "The chemical properties of the elements are a periodic function of their atomic weights"
Mendeleev's Periodic Table Mendeleev made some exceptions to place elements in rows with similar telluriumiodine's properties (tellurium & iodine's places were switched) Missing ElementsMissing Elements: gaps existed in Mendeleev’s table Mendeleev predicted the properties of the “yet to be discovered” elements (scandium, germanium and gallium) Vertical Vertical column s in atomic weight order Horizontal Horizontal rows have similar chemical properties
Problems with Mendeleev’s Table Moseley helped to clarify some of the problems… Why didn't some elements fit in order of increasing atomic mass? Why did elements exhibit periodic behavior?
Henry Moseley English physicist who determined the number of positive charges in the nucleus (protons) by measuring the wavelength of the x-rays given off by certain metals in He was killed by a sniper in Turkey in August 1915 during WWI. Many people think that Britain lost a future Nobel Prize winner. This is because Nobel Prizes, the most prestigious awards for scientific achievement are awarded only to living people.
Moseley and the Periodic Table Protons and Atomic Number: X-ray experiments revealed a way to determine the number of protons in the nucleus of an atom The periodic table was found to be in atomic number order, not atomic mass order!!! This explained tellurium-iodine anomaly ***Moseley was killed in battle in 1915, during WWI. He was 28 years old The Periodic Law The physical and chemical properties of the elements are periodic functions of their atomic numbers
Discovery of the Noble Gases Helium discovered as a component of the sun, based on the emission spectrum of sunlight Freidrich Dorn discovers radon William Ramsay discovers argon Ramsay finds helium on Earth Ramsay discovers krypton and xenon Sir William Ramsay
The LanthanidesThe Lanthanides Early 1900's the elements from cerium (#58) to lutetium (#71) are separated and identified. Also known as the rare earth elements, less than 0.01% naturally occurring. The ActinidesThe Actinides Discovery (or synthesis) of thorium, # 90 to lawrencium #103 Both groups pulled out of the table for space reasons. Periodicity: Elements with similar properties are found at regular intervals within the "periodic" table
Chapter 5 The Periodic Law 5.2 Electron Configuration & The Periodic Table
Sublevel Blocks on the Periodic Table
Easily lose 1 valence electron (Reducing agents) React violently with water React with halogens to form salts the Alkali Metals The Properties of a Group: the Alkali Metals
Easily loses 2 valence electron (Reducing agents) Harder, denser, stronger than Group 1 metals Higher melting points Less reactive than Group 1, but too reactive to be found free in nature the Alkali Earth Metals The Properties of a Group: the Alkali Earth Metals
Chapter 5 The Periodic Law 5.3 Electron Configuration & Periodic Properties
Half of the distance between nuclei in covalently bonded diatomic molecule "covalent atomic radii" Periodic Trends in Atomic Radius: decreases across a period Radius decreases across a period Increased effective nuclear charge due to decreased shielding increases down a group Radius increases down a group Addition of principal quantum levels Determination of Atomic Radius:
Table of Atomic Radii
How to Achieve an Octet… Atoms can form ions by gaining or losing electrons to obtain a stable outer configuration Cation- Positive ion (+) ion Anion- Negative ion (-) ion Ions attract (opposites attract)
Predicting Ionization Metals tend to lose electrons They form cations. Ex: Na, 1s 2 2s 2 2p 6 3s 1 becomes Na +1,1s 2 2s 2 2p 6 Nonmetals tend to gain electrons. They form anions. Ex: O, 1s 2 2s 2 2p 4 becomes O -2, 1s 2 2s 2 2p 6
Electron Transfer: Anions When an atom gains electrons it increases its negative charge so it becomes negatively charged. There are now more electrons than protons. X + e - = X – Ex: Nitrogen Atom+ 7 protons - 7 electrons Nitrogen Ion+7 protons - 10 electrons Neutral - 3 charge
Electron Transfer: Cations When an atom loses electrons, it loses negative charges so it becomes more positively charged. There are now more protons than electrons. X - (e - ) = X + Ex: Potassium Atom+ 19 protons - 19 electrons Potassium Ion+19 protons -18 electrons Neutral + 1 charge
Increases for successive electrons Increases for successive electrons taken from the same atom increase across a period Tends to increase across a period Electrons in the same quantum level do not shield as effectively as electrons in inner levels Irregularities at half filled and filled sublevels due to extra repulsion of electrons paired in orbitals, making them easier to remove decrease down a group Tends to decrease down a group Outer electrons are farther from the nucleus Ionization Energy Ionization Energy - the energy required to remove an electron from an atom
Ionization of Magnesium Mg kJ Mg + + e - Mg kJ Mg 2+ + e - Mg kJ Mg 3+ + e -
Table of 1 st Ionization Energies
Another Way to Look at Ionization Energy
increase across a period Affinity tends to increase across a period decrease down a group Affinity tends to decrease down a group Electrons farther from the nucleus experience less nuclear attraction Some irregularities due to repulsive forces in the relatively small p orbitals Electron Affinity Electron Affinity - the energy change associated with the addition of an electron
Table of Electron Affinities
Ionic Radii Cations Positively charged ions Smaller than the corresponding atom Anions Negatively charged ions Larger than the corresponding atom
Summation of Periodic Trends
Table of Ion Sizes
Electronegativity A measure of the ability of an atom in a chemical compound to attract electrons increase across Electronegativities tend to increase across a period a period decrease down a Electronegativities tend to decrease down a group or remain the same group or remain the same