Elements Ch4.1 8th Pdf

Chapter 4 Section 1

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Describe pure substances

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Describe the characteristics of elements, and give examples

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Explain how elements can be identified

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Classify elements according to their properties

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Element: a pure substance that cannot be separated into simpler substances by physical or chemical means

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Pure substances = one type of particle  The Atom

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Each element has its own characteristic properties

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Characteristic properties include physical (P) and chemical (C) properties (ex: boiling point, density (P); reactivity, flammability (C))

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Some elements share similar properties (examples…)

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Physical properties:  Color, hardness, texture  Melting point, boiling point, density

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Chemical properties:  Flammability  Reactivity (with oxygen)  Reactivity (with acid)

*Figure 2 in text, p. 91 (Cobalt, Iron, Nickel)

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3 major categories:  Metals ▪ Properties: shiny, conduct heat & electricity ▪ Ex: Iron (Fe), Nickel (Ni), Cobalt (Co)  Nonmetals ▪ Properties: dull, do not conduct heat & electricity well ▪ Ex: Sulfur (S), Iodine (I), Neon (Ne)  Metalloids ▪ Properties of both metals & nonmetals ▪ Ex: Silicon (Si), Boron (B), Antimony (Sb)

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What elements are we primarily composed of and in what amounts?  Oxygen 64.6%  Carbon 18.0%  Hydrogen 10.0%

 Nitrogen 3.1%  Calcium 1.9%

 Phosphorus 1.1%  Other 1.3%

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Can you name the 8?  Oxygen 46.6%

 Aluminum 8.1%  Iron 5.0%  Calcium 3.6%  Sodium 2.8%  Potassium 2.6%

 Magnesium 2.1% *What’s missing? Calculate…

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Silicon!  27.7%

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What group of elements are good conductors of electric current?

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What group of elements are brittle & non malleable?

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Shiny?

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Poor conductors of thermal energy?