Periodic Table Chapter 6

Periodic Table A chart that organizes all known elements into a grid of horizontal rows, periods, and vertical columns, groups, arranged by increasing atomic number.

Development of Modern Periodic Table Mendeleev, First atomic table, about 63 elements Organized by atomic mass Connected atomic mass to properties of elements

Medeleev

Periodic Law Henry Moseley, atomic number. Periodic Law: periodic repetition of chemical and physical properties of the elements.

Modern Periodic Table Increasing atomic number Horizontal rows called periods Vertical columns called groups or families Main group, representative, elements Transition Elements

Modern Periodic Table Metals: left side, good conductors, solids usually Metaloids: Stair step, similar properties of metals and nonmetals Nonmetals: right side, gases or dull solids, poor conductors

Alkali Metals Group 1A – excluding hydrogen Shiny, malleable, ductile, good conductors 1 valence electron, readily forms +1 cation Reacts violently with water Reactivity increases as you go down column.

Alkali Earth Metals Group 2A or 2 Ca, Ba, and Sr react with water 2 valence electrons, therefore form +2 cations.

Halogens Highly reactive group 7A or 17 Most are gasses 7 valence electrons, from -1 anion easily

Noble Gasses Group 8A or 18 Formally called inert gasses but actually can react, Xe Full outer energy level

Periodic Trends Atomic Radii Increase down family Why? Decreases down period Higher effective nuclear charge.

Ionization Energy (IE) Energy required to remove an electron from an atom. How strongly an atom’s nucleus holds onto its valence electron. ↑ IE, less likely to form positive ions As you move across period IE increases. Why? Increased Charge has stronger hold on electrons

Ionization Energy (IE) As you move down group the IE decreases. Why? Electron shielding, further away

Octet Rule States that all atoms tend to gain, lose, or share electrons in order to acquire a full set of eight valence electrons. Understanding octet rule helps determine ions. Metals form cations, nonmetals form anions.

Electronegativity Relative ability of the atoms to attract electrons in a chemical bond. Decreases down groups Increases across period Francium least electronegative Fluorine most electronegative