Chemistry Chapter 14 - The Periodic Table A Brief History Dimitri Mendeleev (Russian chemist) First person to publish the classification of the elements that became the Periodic Table -Arranged in order of atomic mass -Elements with similar properties in same horizontal rows -Left empty places for future elements to be discovered Problems arose...Iodine was smaller in mass than Tellurium but had properties similar to Chlorine and Bromine

Henry Moseley Arrange elements by atomic number instead of mass Modern Periodic Law: The chemical and physical properties of the elements are periodic functions of their atomic numbers. Period: A horizontal row on the periodic table. Group: A vertical column on the periodic table. Also known as a family. Transition Elements: Any element with an atom that has an incomplete d subshell or that gives rise to a cation or cations (positive ion) with incomplete d subshells.

Periodic Properties of the Elements Ionization Energy: The energy required to remove the most loosely held electron from the outermost energy level of that atom in the gaseous phase. M(g) + energy --> M + (g) + e - First Ionization Energy: The energy required to remove the first outermost electron. Second Ionization Energy: The energy required to remove the second outermost electron. and so on...

Ionization Energy increases from left to right on the Periodic Table. Ionization Energy increases with every subsequent electron removed. Ionization Energy decreases as you go down the Periodic Table within a group - Shielding Effect. Ionization Energy table on Page 370. Electronegativity: A measure of the ability of an atom of an element that is chemically combined with another element to attract electrons to itself. -Devised by Linus Pauling Metals generally have low electronegativity values, halogens have higher electronegativity values.

Covalent Atomic Radius: The effective distance between the nucleus of the atom and its valence shell when the atom has formed a covalent bond by the sharing of electrons. van der Waals Radius: Half the distance between the nuclei of identical atoms at their point of closest approach when no bond is formed. Ionic Radius: The effective distance from the nucleus of an atom to its outer shell of electrons -Decreases within a Period -Increases within a Group -No clear pattern within a Period -Increases within a Group

Isoelectronic Species: Atoms or ions that have the same electron configuration N -3, O -2, Ne, Na +1, Mg +2, Al +3 is an isoelectronic series. As we move from left to right above, the size of the particle decreases. As atomic number increases within an isoelectronic series, radius decreases.

Metallic vs. Nonmetallic Character Metals are on the left side of the Periodic Table Nonmetals are on the right side of the Periodic Table Metalloids (properties of both metals and nonmetals) are adjacent to the stair-step line in the p block of elements. Most metallic character = lower leftmost side of Periodic Table Most nonmetallic character = upper rightmost side of Periodic Table See Figure on Page 382.