Chapter 4: Atomic structure (or go right to the stacks)

1. Atoms
2. Subatomic particles: electrons, protons, and neutrons [Practice ]
3. Atomic structure [Practice ]
4. Atomic number [Practice ]
5. Atomic mass number [Practice ]
6. Isotopes [Practice ]
7. Atomic mass

Chapter 4

4-1 Atoms

- Atoms are the smallest part of a substance that retains that substance's properties.

4-2 Electrons, Protons, and Neutrons [Practice]

- Electrons (e-) have a negative charge. They were discovered by J. J. Thompson.

- Protons (p+) have a positive charge.

- Neutrons (n^0) have no charge. They were discovered by James Chadwick.

- The nucleus was discovered by Ernest Rutherford in his famous gold foil experiments.

4-3 Atomic Structure [Practice]

- Atoms are made up of protons and neutrons in the nucleus and electrons outside of the nucleus.

- Protons and Neutrons are made up of three quarks each.

4-4 Atomic Number [ Practice]

- An element's atomic number is equal to the number of protons (or electrons) in one atom of that element.

4-5 Mass Number [ Practice]

- Mass numbers are in Atomic Mass Units (AMU's)

- The mass of one proton or neutron is 1 AMU.

- To find the number of neutrons in an atom: (atomic mass number) - (atomic number) = (number of neutrons)

4-6 Isotopes

- For one atom to be an isotope of another, they must share the same number of protons but have different mass numbers (and therefore different numbers of neutrons).

4-7 Atomic Mass

- The reason that the mass numbers on the periodic table are not whole numbers is that they are average masses of all of that element's naturally occuring isotopes.

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