1. Section 2-1 The Chemistry of Life A. Biggs
The Nature of Matter
Section 2-1
The Chemistry of Life
A. Biggs

2. Atoms Atoms are extremely small- 100 million make a row 1cm long
Consists of subatomic particles
Proton - in the nucleus ; has a positive charge
Neutron- in the nucleus carries no charge
Electron- orbits the nucleus & has a negative charge
Atoms

3. Elements are pure substances that consist entirely of one type of atom
Over 100 elements are known
Only about 2 dozen are found in living organisms
Elements are represented by one and two – letter symbols.
Elements

4. An Element in the Periodic Table6 C
Carbon
12.011
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5. The Periodic Table Elements are arranged in increasing atomic number.
Horizontal rows are called periods.
The properties of the elements change as you move across the table.
Vertical columns are called groups or families.
Elements in the same group have similar properties.
The atomic number is the same as the number of protons in the nucleus.
The Periodic Table

7. Isotopes Atoms of elements that have a different number of neutrons
The sum of the protons and neutrons in the nucleus is the atom’s mass number
Isotopes are identified by their mass number
Isotopes have the same chemical properties as the element- because they have the same # of electrons
Isotopes

8. Some isotopes have unstable nuclei and break down at a constant rate over time
This rate is called the
Half-life
Radioactive Isotopes

9. The radiation can be dangerous, but it can also be helpful
Dating fossils
Killing bacteria
Treating cancer
Used as tracers to follow movement of substances in organisms

10. Formed by the chemical combination of two or more elements in definite proportions
Chemical Compounds

11. Chemical formula – shorthand for the name H2O NaCl
The physical and chemical properties of compounds are usually different from elements

12. Chemical Bonds Atoms in compounds are held together by chemical bonds
Bond formation involves the electrons that surround the nucleus
Electron available to form the bonds are called valence electrons
Two main types of bonds
Ionic Bonds
Covalent Bonds
Chemical Bonds

13. Ionic bonds form when one or more electrons are transferred from one atom to another
The atom that loses the electron becomes +
The atom that gains the electron becomes –
NaCl ( Sodium Chloride is an example of ionic bond)
Strong bonds of attraction
Ionic Bonds

15. Covalent Bonds Covalent bonds form when electrons are shared by atoms
When atoms share two electrons a single covalent bond
If four electrons are shared double covalent bond
If six electrons triple covalent bond
Molecules are the formed by covalent bonds
smallest unit of most compounds
Covalent Bonds

16. Van der Waals Forces Intermolecular forces of attraction
Not as strong as ionic or covalent bonds, but they can hold molecules together.
Van der Waals Forces