Elements compounds and mixtures

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Lead has two charges listed, +2 and +4. This is a sample of lead (II) chloride (PbCl2). Two or more elements bonded in a whole-number ratio is a COMPOUND.

This compound is formed from the +4 version of lead. This is lead (IV) chloride (PbCl4). Notice how both samples of lead compounds have consistent composition throughout? Compounds are homogeneous!

منگل، 18 ذو القعد، 1436

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Types of Compounds

Ionic: made of metal and nonmetal ions. Form an ionic crystal lattice when in the solid phase. Ions separate when melted or dissolved in water, allowing electrical conduction. Examples: NaCl, K2O, CaBr2

Molecular: made of nonmetal atoms bonded to form a distinct particle called a molecule. Bonds do not break upon melting or dissolving, so molecular substances do not conduct electricity. EXCEPTION: Acids [H+A- (aq)] ionize in water to form H3O+ and A-, so they do conduct.

Network: made up of nonmetal atoms bonded in a seemingly endless matrix of covalent bonds with no distinguishable molecules. Very high m.p., don’t conduct.

منگل، 18 ذو القعد، 1436

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Ionic Compounds

منگل، 18 ذو القعد، 1436

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Molecular Compounds

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Network Solids

Network solids are made of nonmetal atoms covalently bonded together to form large crystal lattices. No individual molecules can be distinguished. Examples include SiO2 (quartz). Corundum (Al2O3) also forms these, even though Al is considered a metal. Network solids are among the hardest materials known. They have extremely high melting points and do not conduct electricity.

منگل، 18 ذو القعد، 1436

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Examples of some formula

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منگل، 18 ذو القعد، 1436

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Mixtures

Heterogeneous mixtures are not uniform throughout.

Homogeneous mixtures are uniform throughout.

Homogeneous mixtures are called solutions.

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منگل، 18 ذو القعد، 1436