3 Elements and Compounds - This Old Earth

3 Elements and Compounds

This reclining Buddha in

Thailand is made of gold.

Chapter Outline

3.1 Elements 3.2 Introduction to the Periodic Table 3.3 Compounds and Formulas

Elements and Atoms

An element is a fundamental substance that cannot be broken down by chemical means

into a simpler substance.

Elements are the building blocks of matter.

Elements can occur naturally or be synthesized in labs. The smallest unit of an element that retains its properties and chemical behavior is called an atom.

Atoms are made up of subatomic particles, but they do not have the properties of the element.

Elements

Currently, 118 elements are known. 88 of these elements are naturally occurring.

At room temperature, only bromine (Br) and mercury (Hg) are liquids.

11 elements are gases: hydrogen (H2), nitrogen (N2), oxygen(O2), fluorine (F2), chlorine (Cl2), helium (He), neon (Ne), argon (Ar), krypton (Kr), xenon (Xe) and radon (Rn).

Elements

Ten elements make up almost 99 % of the mass of the Earth's crust, seawater and atmosphere.

Oxygen accounts for about 20 % of the atmosphere and is found in nearly all rocks, sand and soil.

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