Elements, Atoms & Molecules

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Elements

Back 1

Pure substances that cannot be broken down into any other substance.

Identified by its physical & chemical properties

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Atom

Back 2

Basic particle from which all elements are made.

Smallest unit that still maintains the properties of that element.

Contains protons and neutrons surrounded by a cloud of moving electrons

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Molecules

Back 3

Groups of 2 or more atoms held together by a chemical bond

Ex. ) Water (H2O)

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Compounds

Back 4

2 or more elements chemically combined in a set ratio. They have properties that are different from those of the uncombined elements

Ex.) Table sugar
Carbon
Hydrogen
Oxygen

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Mixtures

Back 5

2 or more substances - elements, compounds - that are together, but not chemically combined. The substances maintain their individual properties, not combined in a set ratio. They can be separated into their component parts

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Heterogeneous

Back 6

You CAN "SEE" the different parts

Ex.) soil
salad

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Homogeneous

Back 7

You CANNOT "SEE" the different substances

Ex.) Kool Aid
Air

Front 8

Modern Atomic Theory

Back 8

Developed & revised over the last 2 centuries as a series of models.

Was developed from experimental evidence.

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Nucleus

Back 9

Contains neutrons & protons

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Neutrons

Back 10

Electrically neutral particle, no charge

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Protons

Back 11

Positively charged particles in the nucleus

Front 12

Electrons

Back 12

Negatively charged particles circulating (moving) in a large cloud layer outside the nucleus. The outer most electrons make the element chemically reactive.