Check Understanding Question Task: Individually, read the following question and write down your answer in your notes, to check your understanding of physical and chemical change.

How can we know what atoms look like if we can’t see them? Focusing Question How can we know what atoms look like if we can’t see them?

Models or

How can we know what atoms look like if we can’t see them? Lead Gold *Alchemists tried to use experiments to turn lead into gold*

Introducing Atomic Theory How can we know what atoms look like if we can’t see them? Introducing Atomic Theory Greek philosopher Democritus in 400 B.C. used the word atomos to describe the smallest particles that could not be broken further. Atomos means “indivisible.”  Democritus stated that each type of material was made up of a different type of atomos. These different particles, he believed, gave each material its own unique set of properties.

How can we know what atoms look like if we can’t see them? Dalton’s Model -Each element is made up of atoms of the same mass (weight) -Different elements have different masses Each atom is a tiny sphere Billiard (pool) Ball Model

Hydrogen

How can we know what atoms look like if we can’t see them? Thompson’s Model -Conducted the Cathode Ray Experiment -Discovered that inside the atom are negatively charged electrons Raisin Bun

How can we know what atoms look like if we can’t see them? Rutherford’s Model Solar System Model -Conducted a Gold Foil Experiment -Discovered that the positive particles are in the center of the atom, which are called protons

How can we know what atoms look like if we can’t see them? Bohr’s Model Atomic Model -Suggested that electrons do not randomly travel in an atom -Electrons travel in electron shells

Rules for Creating Bohr Models of Elements How can we know what atoms look like if we can’t see them? Rules for Creating Bohr Models of Elements The row number of the periodic table that the element is in, tells you how many shells you need The 1st electron shell can only hold 2 electrons The 2nd and 3rd electron shells can only hold 8 electrons You indicate (write) the number of protons and neutrons in the nucleus