Periodic Table Trends

• Arrangement of the elements in order of their atomic numbers so that elements with similar properties fall in the same column, or group

•What is it?

• Group: vertical column of periodic table• Period: horizontal row of periodic table• Valence Electrons: electrons that occupy the highest energy level

• Up to 8• Atoms want to have full valence shell

• Ion: atom that has gained or lost an electron• Cation: atom loses electron; has + charge• Anion: atom gains electron: has - charge

• Important Terms

• Silvery appearance• Can be cut by knife• Highly reactive with water• Usually not found in nature as a pure element• Always forms cations with +1 charge

• NOTE: Hydrogen, even though it is listed in group one, is NOT an alkali metal

• Alkali metals•Group 1

• Similar to alkali metals, but harder, denser, and stronger

• Also not usually found in nature as a pure element• Always forms cations with +2 charge

• Alkaline-earth metals•Group 2

• Good conductors of electricity• High luster• Less reactive than alkali and alkaline-earth metals

• Some do not easily form compounds!• Forms cations with varying charges

• Transition metals•Groups 3-12

• Most reactive non-metals• React with metals to form salts• Always form anions with -1 Charge

• Halogens•Group 17

• All electron shells full• Little to no chemical reactivity• Always has neutral charge

• Noble Gases•Group 18

• Do not easily fit in any particular group, so these elements are usually separated in it’s own area on the periodic table

• All actinides are radioactive• Only 4 are found naturally

•Lanthanides and Actinides

• Distance from the nucleus to the outer edge of electron cloud

• Increases as you go read down the group• Decreases as you read across the period

• Why?

• Atomic radiiPeriodic Properties

• Distance from the nucleus to the outer edge of electron cloud after an atom has gained or lost an electron

• Groups 1-13 form cations (+)• Groups 15-17 form anions (-)

• Increase as you go read down the group• Cationic radii decrease as you read across the period• Anionic radii increase as you read across the period

• Why?

• Ionic radii

Periodic Properties

• The energy needed to remove an electron from an atom

• Decreases as you read down a group• Increases as you read across a period

• Why?

• Ionization energyPeriodic Properties

• Energy change that occurs when an electron is gained by a neutral atom

• Represented as a negative number• Decreases slightly as you read down a group• Greatly increases as you read across a period

• Why?

• Electron AffinityPeriodic Properties

• The ability of an atom to attract an electron; only a property of atoms in compounds

• Decreases as you read down a group• Increases as you read across a period

• Why?

• ElectronegativityPeriodic Properties