Composition of Matter Atomic theory – the beginnings November 2nd, 2006 Composition of Matter Atomic theory – the beginnings

Drill When you compare atoms and compounds to the English language: elements are like __________ Compounds are like __________ Atoms are the smallest example of __________ Molecules are the smallest example of __________

How Chemists Figured out Atomic Theory Hypothesis (Hø) A prediction It’s possible to test it Explains observations * Scientific Law A fact of nature NOT an explanation BUT can be used as proof of an explanation 2. Theory An explanation Many observations support it

Hypothesis If I study and do my homework I will do well in Ms. Pallandre’s chemistry class You can test what the effect will be of studying and doing homework (indep. vars.) Dep. var. = grade Observation would be the grade & study habits

Theory Students that do well in school have good study habits People who study education have written papers saying this An explanation of why students do well

Chemistry History Saw that when elements were combined to form compounds, the ratios that were used up were whole numbers. John Dalton

JOHN DALTON’s ATOMIC THEORY What he was right about & wrong about 5 MAIN POINTS

Dalton’s atomic theory Elements are made of tiny particles called atoms All atoms of a given element are identical The atoms of a given element are different from those of any other element

Dalton’s atomic theory Atoms of one element can combine with atoms of other elements to form compounds. A given compound always has the same relative numbers of types of atoms. Atoms cannot be created, divided into smaller particles, nor destroyed in the chemical process. A chemical reaction simply changes the way atoms are grouped together.