1. Chapter 3 Atoms and Elements
3.3
The Atom
Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition Copyright © 2012 by Pearson Education, Inc.

2. Dalton's Atomic Theory In Dalton's atomic theory, atoms
are tiny particles of matter
of an element are similar to each other and different from other elements
of two or more different elements combine to form compounds
are rearranged to form new combinations in a chemical reaction
Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition Copyright © 2012 by Pearson Education, Inc.

3. Subatomic Particles Electrical Charges
Atoms contain subatomic particles.
Protons have a positive (+) charge.
Electrons have a negative (–) charge.
Neutrons are neutral.
Like charges repel and unlike charges attract.
Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition Copyright © 2012 by Pearson Education, Inc.

4. Rutherford's Gold Foil Experiment
In Rutherford’s gold foil experiment, positively
charged particles
were aimed at atoms of gold
mostly went straight through the atoms
were deflected only occasionally
Conclusion:
There must be a small, dense, positively charged nucleus in the atom that deflects positive particles that come close.
Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition Copyright © 2012 by Pearson Education, Inc.

5. Rutherford's Gold Foil Experiment
Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition Copyright © 2012 by Pearson Education, Inc.

6. Structure of the Atom An atom consists of
a nucleus that contains protons and neutrons
electrons in a large, empty space around the nucleus
Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition Copyright © 2012 by Pearson Education, Inc.

7. Mass of the Atom Atomic mass unit
1 atomic mass unit (amu) has a mass equal to 1/12 of the mass of the carbon-12 atom.
a proton has a mass of about 1 (1.007) amu.
a neutron has a mass of about 1 (1.008) amu.
an electron has a very small mass, amu.
Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition Copyright © 2012 by Pearson Education, Inc.

8. Subatomic Particles in the Atom
Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition Copyright © 2012 by Pearson Education, Inc.

9. Learning Check
Which of the following subatomic particles fits each of the descriptions below:
proton, neutrons, or electrons
A. found outside the nucleus
B. has a positive charge
C. has mass but no charge
Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition Copyright © 2012 by Pearson Education, Inc.

10. Solution
Which of the following subatomic particles fits each of the descriptions below:
proton, neutrons, or electrons
A. found outside the nucleus electrons
B. has a positive charge protons
C. has mass but no charge neutrons
Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition Copyright © 2012 by Pearson Education, Inc.