Atoms and Elements Chapter 2 Pgs. E34-E49

What are Atoms and Elements? pgs. E36-E43

Atoms aren’t a New Idea Democritus (400 B.C.), a Greek philosopher, had a theory that matter is made of tiny particles that can’t be divided and are too small to see. Aristotle also a Greek philosopher didn’t buy the theory Neither one based their theories on any experimental evidence.

Democritus

Aristotle

John Dalton Early 1800’s Proposed an atomic theory of matter that was based on experimental evidence. Dalton’s atomic theory is that all matter is made up of tiny particles called atoms.

Size of an atom. Atoms are tiny. Over five million atoms could fit on the head of a straight pin.

Subatomic Particles Atoms are teensy weensy; however, there are even smaller particles on the inside of the atom. nucleus – center of the atom proton – positive charged particle inside of the nucleus neutron – a particle inside of the nucleus with no charge electron –a particle outside the nucleus with a negative charge

Atoms Atoms are the smallest unit of an element that has all the properties of that element.

Niels Bohr proposed a model of the structure of an atom in 1913.

Niels Bohr’s Atom Structure Model Electrons circle the nucleus The electrons path is called an orbit/energy levels Low energy electrons orbit close to the nucleus High energy electrons orbit farther away from the nucleus

Protons and neutrons have a mass that is almost 2000 times the mass of an electron. Proton Man Electron Man

The attraction between the positive charge of the protons and the negative charge of the electrons is part of what holds atoms together.

If an atom has more protons than electrons it has a positive charge. If an atom has more electrons than protons it has a negative charge. An atom that has an equal amount of protons and electrons is a neutral atom

79 – atomic number = # of protons in one atom of that element Au – chemical symbol Gold- element name An element is a substance made up of only one kind of atom. Gold is an element

In your book look at the chart on Pg. E 41 to see some more common elements. Halogen/Salt Iodine I Metal Platinum Pt Gas Hydrogen H

Metalloid Antimony SB

Molecules Two or more atoms of the same kind linked together form a molecule that is in a pure state. Example: Oxygen O 2

A molecule is also formed when two or more elements are linked together. Explore here to view some molecules”

Properties of Metals Luster-shiny

Are ductile-able to be hammered thin

Are malleable-can be bent and molded

Conduct electricity and heat

What Are Compounds? Lesson 2 pgs. E46-E49

Dmitri Mendeleev Russian Chemist Organized elements into an orderly table in 1869.

The Period Table pgs. E46-E-47 Elements are arranged in order of atomic number. Elements with similar properties are in the same column Elements on the left side of the table, except hydrogen, are metals Elements on far right are nonmetals. Metalloids have properties of both metals and nonmetals.

Check out these interactive periodic tables to learn more about the elements. I liked the second one better. com/ ements/pages/pertable_j.htm

Compounds A substance made of the atoms of two or more elements. Use your periodic table on pgs. E46-E47 to see if you can match the compounds and their names

How to read a Formula for a compound 1.Chemical formulas are used to describe the types of atoms and their numbers in an element or compound. 2.The atoms of each element are represented by one or two different letters. 3.When more than one atom of a specific element is found in a molecule, a subscript is used to indicate this in the chemical formula.

2 atoms of Hydrogen + 1 atom of Oxygen = 1 molecule of water H 2 O H 2 O + + = =

More Chemical Compounds Carbon Dioxide > CO 2 Ammonia > NH 3 Sugar > C 6 H 12 O 6 Rubbing Alcohol > C 3 H 7 OH

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