Chapter 2: Small Molecules and the Chemistry of Life
All matter is composed of atoms. Atoms are
composed of:
• Electrons—negligible mass; negative charge
• The atomic nucleus:
• Protons—have mass, positive charge
• Neutrons—have mass, no charge
Element: fundamental substance containing only one kind of atom.
The number of protons (atomic number) identifies an element.
Number of protons and electrons determines how an element behaves in
chemical reactions.
Mass number = protons + neutrons
Isotopes: Forms of an element with different numbers of neutrons, and
thus different mass numbers.
Example: carbon isotopes
12^C has 6 neutrons
13^C has 7 neutrons
14^C has 8 neutrons
Hydrogen bonds are weak.
There are 6 electrons its valent compound.
All matter is composed of atoms. Atoms are
composed of:
• Electrons—negligible mass; negative charge
• The atomic nucleus:
• Protons—have mass, positive charge
• Neutrons—have mass, no charge
Element: fundamental substance containing only one kind of atom.
The number of protons (atomic number) identifies an element.
Number of protons and electrons determines how an element behaves in
chemical reactions.
Mass number = protons + neutrons
Isotopes: Forms of an element with different numbers of neutrons, and
thus different mass numbers.
Example: carbon isotopes
12^C has 6 neutrons
13^C has 7 neutrons
14^C has 8 neutrons
Hydrogen bonds are weak.
There are 6 electrons its valent compound.
