1. Structure of Atoms
Page 55 of INB

2. Why do isotopes of the same element have different masses?
Essential Question:
Why do isotopes of the same element have different masses?

3. Parts of the atom:
Nucleus: center of the atoms contains protons and neutrons.
Proton has a positive charge, neutron has no charge (neutral).
Electrons move around the outside of nucleus, orbit, almost no mass.
Unreacted atoms have a neutral charge.
# protons = # electrons
# of protons determine the element.
If an atom gains or loses an electron it is called an ion.

4. Atomic Number:
Tells the number of protons in the nucleus, and equals the number of electrons in a neutral atom.
All atoms of the same element have the same atomic number.
Atomic number can not change, because it would change the element.

5. Mass Number:
Equals the # of protons plus the number of neutrons.
Mass # can be different, because the number of neutrons can be different.

6. Isotopes: Atoms with different # of neutrons.
Atoms of the same element can have different masses, because of different # of neutrons.
Can be written two different ways
Uranium-235 or 235 U 92
Number of neutrons can be calculated by subtracting atomic number from mass number.

7. Atomic Structure Review.
List the 3 subatomic particles and their charges.
How can you determine the number of protons, electrons, and neutrons from the atomic number and mass number.
How can the mass of atoms of the same element have different masses.
Determine the # of protons and # electrons for the following.
a) Carbon b) Chlorine c) Argon d) Mercury
Calculate the number of neutrons for the following isotopes.
Carbon-14 b) Nitrogen-15 c) Sulfer-35 d) Calcium-45

8. Atomic Structure Review.
List the 3 subatomic particles and their charges.
How can you determine the number of protons, electrons, and neutrons from the atomic number and mass number.
How can the mass of atoms of the same element have different masses.
Determine the # of protons and # for the following.
a) Carbon b) Chlorine c) Argon d) Mercury
Calculate the number of neutrons for the following isotopes.
Carbon-14 b) Nitrogen-15 c) Sulfer-35 d) Calcium-45