Ch 5 The Periodic Law 5.1 History of the Periodic Table Mendeleev Proposed/arranged elements into rows based on increasing mass (like periods) and into columns due to similar properties (like groups) Prediction, not all elements discovered yet Left spaces for new elements!

Mosley Working with Ernest Rutherford and spectra of metals Saw arranged by increasing nuclear charge, p+ Led to atomic number (not atomic mass) to organize periodic table Periodic Law: elements arranged in order of increasing atomic number, there is a periodic repetition of physical/chemical properties

Noble Gases (18 or 8A, full p) Added to periodic table, missed because unreactive Lanthanides (4f) 14 elements atomic # 58-71 Added in 1900s Actinides (5f) 14 elements atomic # 90-103 Belong in pd 6-7 and groups 3-4, but placed below periodic table Periodicity Arrangement of e- around nucleus

5.2 E- Configuration and the Periodic Table Recall e- configurations/shapes See pattern of e- configuration in periodic table!

s- orbital Alkali: Group 1 or 1A Alkaline earth metals: Group 2 or 2A From Arabic al aquali= the ashes Metals with 1e- Highly reactive metals Alkaline earth metals: Group 2 or 2A Harder/denser with 2e- Still reactive H and He: s-block but gases/ do not share properties

d- block elements Transition metals: Group 3-12 (B group elements) Metals 80% periodic table Properties: good conductors heat/electricity, reflect light with luster/sheen, ductile, malleable

p-block: Group 13-17 or 3A-7A Main- group elements Non metals or metalloids Halogens: Group 7A or 17 are the most reactive non-metals Noble gas: Group 18 or 8A are the most stable elements

f-block Inner transition metals Below main body of periodic table 14e- Previously called rare-earth metals (misleading bc more abundant than other elements) Lanthanides Actinides

5.3 E- Configuration and Periodic Properties Atomic Radii: ½ distance between nuclei of identical bonded atoms Period: decreases as move from left to right in period Group: increases as move down group Same for atomic size!!!

Ionization: Energy to remove e- Period: increases from left to right in period Group: decrease from top to bottom in group

Electron affinity: E added when an e- is added to neural atom; energy given off is neg # Period: most periods except halogens gain e-; decreases left to right Group: added with greater difficulty down a group usually, increases down group

Ionic radii: cations are smaller, anion are larger Period: cations/anions decrease in size from left to right in period Group: increase in ionic radii from top to bottom in group

Electronegativity: how easy to attract e- Period: increases from left to right in a period Group: decrease from top to bottom in a group