Chemistry 8.1 Molecular Compounds

– These toy models are made from circular pieces joined together in units by sticks. Atoms can also be arranged in different ways to make a variety of products.

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• Molecules and Molecular Compounds

– How are the melting points and boiling points of molecular compounds different from those of ionic compounds?

• Monatomic elements

– Exist in nature as single atoms

– Example:

• noble gases

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– covalent bond

• atoms held together by sharing electrons

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– Molecule

• A neutral group of atoms joined together by covalent bonds. – Air contains oxygen molecules.

» O2

– diatomic molecule

• a molecule consisting of two atoms. – Examples:

» Oxygen

» Chlorine

» hydrogen

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• molecular compound – composed of molecules

» Held together by covalent bonds

– Examples:

» Water

» carbon monoxide

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– Molecular compounds

• tend to have relatively lower melting point than ionic compounds.

• tend to have relatively lower boiling point than ionic compounds.

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• Ethane, a component of natural gas, is also a molecular compound.

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• Molecular Formulas

– What information does a molecular formula provide?

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• molecular formula

– the chemical formula of a molecular compound.

– shows how many atoms of each element a molecule contains.

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• Formulas of Some Molecular Compounds 8.1

Quiz.

1. Compared to ionic compounds, molecular compounds tend to have relatively

A. low melting points and high boiling points.

B. low melting points and low boiling points.

C. high melting points and high boiling points.

D. high melting points and low boiling points.

2. A molecular compound usually consists of

A. two metal atoms and a nonmetal atom.

B. two nonmetal atoms and a metal atom.

C. two or more metal atoms.

D. two or more nonmetal atoms.

3. A molecular formula shows

A. how many atoms of each element a molecule contains.

B. a molecule's structure.

C. which atoms are bonded together.

D. how atoms are arranged in space.

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