1. Molecules and Molecular Compounds
8.1
Molecules and Molecular Compounds
Molecules and Molecular Compounds
How are the melting points and boiling points of molecular compounds different from those of ionic compounds?

2. Molecules and Molecular Compounds
8.1
Molecules and Molecular Compounds
In nature, matter takes many forms. The noble gases, including helium and neon, are monatomic. That means they exist as single atoms.
The noble gases, including helium and neon, are monatomic. That means they exist as single atoms. Helium, being less dense than air, is often used to inflate balloons. The colors produced in what we commonly call neon lights are a result of passing an electric current through one or more noble gases.

3. Molecules and Molecular Compounds
8.1
Molecules and Molecular Compounds
Some compounds are so different from ionic compounds that attractions between ions fail to explain their bonding.
The atoms held together by sharing electrons are joined by a covalent bond.

4. Molecules and Molecular Compounds
8.1
Molecules and Molecular Compounds
A molecule is a neutral group of atoms joined together by covalent bonds. Air contains oxygen molecules.
A diatomic molecule is a molecule consisting of two atoms. An oxygen molecule is a diatomic molecule.

5. Molecules and Molecular Compounds
8.1
Molecules and Molecular Compounds
A compound composed of molecules is called a molecular compound. Water and carbon monoxide are molecular compounds.
Water is a molecular compound with molecules composed of two hydrogen atoms and one oxygen atom. Carbon monoxide is a molecular compound with molecules composed of one carbon atom and one oxygen atom.

6. Molecules and Molecular Changes
8.1
Molecules and Molecular Changes
Molecular compounds tend to have relatively lower melting and boiling points than ionic compounds.

7. Molecules and Molecular Compounds
8.1
Molecules and Molecular Compounds
Sodium chloride, which is an ionic compound, and water, which is a molecular compound, are compared here. Interpreting Diagrams How do molecular compounds differ from ionic compounds?

8. Molecules and Molecular Changes
8.1
Molecules and Molecular Changes
Ethane, a component of natural gas, is also a molecular compound.
Ethane is a component of natural gas. Inferring What information about the ethane molecule given by its molecular formula C2H6 is also given by the drawing shown here?

9. 8.1
Molecular Formulas
Molecular Formulas
What information does a molecular formula provide?

10. A molecular formula is the chemical formula of a molecular compound.
8.1
Molecular Formulas
A molecular formula is the chemical formula of a molecular compound.
A molecular formula shows how many atoms of each element a molecule contains.

11. 8.1
Molecular Formulas
Ammonia (NH3) is used in solution as a cleaning agent. You can represent the ammonia molecule by its molecular formula, its structural formula, a space-filling molecular model, a perspective drawing, or by a ball-and stick molecular model.

12. 8.1 Formulas of Some Molecular Compounds Molecular Formulas
The formula of a molecular compound indicates the numbers and kinds of atoms. The arrangement of the atoms within a molecule is called its molecular structure. Using Models Which of these molecules has the greatest number of oxygen atoms?

13. 8.1 Section Quiz.
1. Compared to ionic compounds, molecular compounds tend to have relatively
low melting points and high boiling points.
low melting points and low boiling points.
high melting points and high boiling points.
high melting points and low boiling points.

14. 8.1 Section Quiz
2. A molecular compound usually consists of
two metal atoms and a nonmetal atom.
two nonmetal atoms and a metal atom.
two or more metal atoms.
two or more nonmetal atoms.

15. 8.1 Section Quiz
3. A molecular formula shows
how many atoms of each element a molecule contains.
a molecule's structure.
which atoms are bonded together.
how atoms are arranged in space.

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