Periodic Table

History Dmitri Mendeleev (1869) arranged the known elements based on atomic mass Elements with similar properties occurred in regular intervals (periodic)

Henry Mosely 1914- rearranged the table based on atomic number once protons were discovered

Atomic number- number of protons in one atom of the element Chemical symbol- Sometimes one letter, sometimes two letters, first letter is always capitalized Atomic mass- average mass for all naturally occurring isotopes; this is not the same as mass number

Element arrangement

Metals left of the zigzag few electrons in outer energy level most are solid at room temperature shiny, good conductors, ductile (can be made into a wire), malleable

Nonmetals right of the zigzag (except hydrogen) have almost complete or complete outer level of electrons many are gasses at room temperature dull, poor conductors, not ductile, not malleable

Metalloids border the zigzag line half complete set of electrons in outer level semiconductors share properties with metals and nonmetals

A period is a row (left to right) Seven of them Periods A period is a row (left to right) Seven of them properties like conductivity and reactivity change across the period Densest elements are in the middle

Groups Groups are columns (top to bottom) 18 groups Also called family Elements in the same group have similar physical and chemical properties Same number of valence electrons (electrons in the outermost shell)

Valence electrons allow chemical bonding Group 1 has 1 valence electron Group 18 has a full set of valence electrons Group 1 is very reactive, while group 18 does not react with other elements

Group 2 = alkaline-earth metals Groups 3-12 = transition metals Main Names Group 1 = alkali metals Group 2 = alkaline-earth metals Groups 3-12 = transition metals Groups 13-16 = named for top element in that group (ex: carbon group) Group 17 = halogens Group 18 = noble gases

Exothermic reactions- energy is released Chemical Reactions Exothermic reactions- energy is released Product can give off light and/or heat Endothermic reactions- energy is absorbed Energy is in the reactants

During chemical reactions bonds between atoms break During chemical reactions bonds between atoms break. Then, the atoms rearrange to make new substances. The new substance has different physical and chemical properties that the original. Examples: precipitate forms, odor change, gas produced, etc.

Ways to speed up a reaction Increasing concentration Increasing surface area (crushing/grinding) Increase temperature Adding a catalyst

Chemical formulas Symbols and numbers that represent substances Examples: Water = H2O Salt = NaCl Glucose = C6H12O6 Baking Soda = NaHCO3

Chemical Equations

RAP Reactants  Product

Subscript Coefficient The law of conservation of mass means the same number of atoms must be on both side of the equation. Coefficient Subscript

Video Help Beginning help: https://www.youtube.com/watch?v=yA3TZJ2em6g More examples: https://www.youtube.com/watch?v=eNsVaUCzvLA