5 Periodic Law Henry Moseley, atomic number. Periodic Law: periodic repetition of chemical and physical properties of the elements.
6 Modern Periodic Table Increasing atomic number Horizontal rows called periodsVertical columns called groups or familiesMain group, representative, elementsTransition Elements
7 Modern Periodic TableMetals: left side, good conductors, solids usuallyMetaloids: Stair step, similar properties of metals and nonmetalsNonmetals: right side, gases or dull solids, poor conductors
8 Alkali Metals Group 1A – excluding hydrogen Shiny, malleable, ductile, good conductors1 valence electron, readily forms +1 cationReacts violently with waterReactivity increases as you go down column.
9 Alkali Earth Metals Group 2A or 2 Ca, Ba, and Sr react with water 2 valence electrons, therefore form +2 cations.
10 Halogens Highly reactive group 7A or 17 Most are gasses 7 valence electrons, from -1 anion easily
11 Noble GassesGroup 8A or 18Formally called inert gasses but actually can react, XeFull outer energy level
12 Periodic Trends Atomic Radii Increase down family Why? Decreases down periodHigher effective nuclear charge.
13 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 ionsAs you move across period IE increases.Why?Increased Charge has stronger hold on electrons
14 Ionization Energy (IE) As you move down group the IE decreases.Why?Electron shielding, further away
15 Octet RuleStates 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.
16 ElectronegativityRelative ability of the atoms to attract electrons in a chemical bond.Decreases down groupsIncreases across periodFrancium least electronegativeFluorine most electronegative