Chapter 4

Periodic Properties of the Elements

The Development of the Periodic TableDmitri Mendeleev and Julius Lothar Meyer independently came to the same conclusion about how elements should be grouped.Mendeleev was born in Siberia and studied at St. Petersburg State University where he became a Professor of General Chemistry once he finished his degree. J. Lothar Meyer came from a medical family of Oldenburg, Germany, and first pursued a medical degree. In medical school he became interested in chemistry, especially physiological topics like gases in the blood.

Development of the Periodic TableBoth were writing text books when they realized if the elements were arranged in order of increasing atomic mass, there was a periodicity to the properties. Lothar Meyer (18301895) and Dmitri Mendeleev (18341907) both worked at the University of Heidelberg under the direction of Robert Bunsen, only 5 years apart.

Mendeleevs table as published in 1869, with many gaps and uncertainties The Development of the Periodic Table

Table Rotated 90 degrees shown in text books in 1898 (From F. Wilhelm Ostwald, Grundriss der Allgemeine Chemie.) The Development of the Periodic Table

Mendeleevs Periodic Law allows us to predict what the properties of an element will be based on its position on the table.It doesnt explain why the pattern existsQuantum Mechanics is a theory that explains why the periodic trends in the properties existThe Development of the Periodic Table X-ray experiments by Henry Moseley showed elemental properties vary with atomic numbers and not mass. Elements in modern periodic tables are arranged in order of atomic number and not atomic mass.

The Development of the Periodic Table

IUPAC Periodic Table of the Elements

The Development of the Periodic Tablelead-208 nuclei were bombarded with zinc-70 nuclei in a heavy ion accelerator.Element 112, copernicium was first made by research scientists at the Heavy Ion Research Laboratory in Darmstadt, Germany in 1996.A single atom of copernicium-277 resulted.Atoms of copernicium-281 and copernicium-284 have been recorded more recently as decay products of flerovium. Copernicium is named after astronomer and mathematician Nicolaus Copernicus.

The Development of the Periodic TableElement 114, flerovium was made by fusion of calcium-48 with plutonium-244. In 1998 a beam of calcium ions was accelerated in the Russian Dubna cyclotron to 10% of the speed of light before hitting the plutonium target. The experiment ran 6 months. In the first 40 days, 5 x 1018 calcium ions were fired at the plutonium, resulting in a single atom of flerovium-289, which existed for 30.4 seconds before decaying.Later, two atoms of flerovium-288 were made, allowing an approximate half-life of 2 seconds to be estimated for this isotope. Enough has been made to determine it exists, but too little assess its properties with certainty.

The Development of the Periodic TableElement 116, livermorium, was first made in Dubna, Russia in July 2000 in a collaboration between the Joint Institute for Nuclear Research in Dubna and Lawrence Livermore National Laboratory, Calif.In 2011 The International Union of Pure and Applied Chemistry (IUPAC) finally, after years of work, accepted the discovery.This was a fusion between a calcium-48 beam with curium-248. In the first exp. a single atom of livermorium-292 was detected and it existed for 46.9 ms before decaying to flerovium-288. In an experiment that lasted a year, two further atoms of Lv-292 were made. One existed for 125.5 ms and the second for 55.0 ms. By 2005, 30 atoms of livermorium had been made.

Effective Nuclear ChargeEach electron in a multielectron atom experiences both the attraction to the nucleus and repulsion by other electrons in the atomThese repulsions cause the electron to have a net reduced attraction to the nucleus it is shielded from the nucleus

The closer an electron is to the nucleus the more attraction it experiences.Inner [core] electrons are better at shielding valence electrons [outer] than valance electrons are at shielding each other. Zeff = Z S where Z = atomic number and S = screening constantEffective Nuclear Charge

Effective Nuclear Charge

Effective Nuclear Chargeelectrons in orbitals in the same shell (n) dont shield each other as well as the inner [core]electrons increasenot muchchange

Trends in Atomic Radius

Figure 8.5 from Raymond Chang Chemistry

Neutral Atomic Radiielectrons in orbitals in the same shell (n) dont shield each other as well as the inner [core] electrons decreaseincrease

Size Comparison of Cations and Anions

Ion Sizeremove an electron and the cation gets smaller because there are more protons to pull the electrons in tighteranions increaseincreasecations decreaseadd an electron and the anion gets larger because there are fewer protons to hold the electrons in close

Trends in First Ionization Energy

Trends in First Ionization Energy

Ionization Energyenergy required to remove an electron from a neutral atom.increaseincrease

Electron AffinityM(g) + 1e M1(g) + EADefined to give off energy (), but may actually require energy (+)The more energy that is released the more negative the number, the larger the electron affinitysome alkaline earth metals and all Nobel gases require energy The ease with which an atom gains an electronElectron Affinity the energy change that occurs when an electron is added to a gaseous neutral atom

Trends in Electron Affinity Energies

Trends in Electron AffinityAlkali metals decrease EA down the columnGenerally EA becomes more negative from left to rightHighest EA in any period = halogenGroup 5A generally lower EA than expected because extra electron must pairGroup 2A and 8A generally positive EA because the added electron goes into higher energy level or sublevel

Trends in Metallic Characters

* Figure 7.1 Discovering the elements. * Figure 7.4 Variations in effective nuclear charge for period 2 and period 3 elements.