Structure of the Atom

1
Structure of the Atom

• Sections 17.1-17.4

2
Review

• Elements are made up of only one type of atom.
• All elements are listed on the Periodic Table.
• Each element is represented by its atomic symbol.

3
Atomic Symbols

• Some symbols come from the elements name.
• Example C is for Carbon
• Others come from the elements Latin name.
• Example
• Au is for Gold (aurum)
• Pb is for Lead (plumbum)

4
About Atoms

• Atoms are so small they cant be seen with
  visible light.
• Photographs of atoms can be seen by a scanning
  tunneling microscope.
• The atom is actually made up of smaller subatomic
  particles.
• Proton
• Electrons
• Neutrons

5
The Nucleus

• Nucleus contains protons and neutrons.
• The electrons can be found surrounding the
  nucleus in the electron cloud.
• Electrons are very far away from the nucleus.
• There is actually a lot of empty space between
  the nucleus and electrons.

6
Subatomic Particles
7
Isotopes

• The number of protons tells us the atomic number
  of the atom.
• The mass number is the total number of protons
  and neutrons in the nucleus.
• Atoms can have different numbers of neutrons.
• Atoms that have different numbers of neutrons are
  called isotopes.

8
Isotopes

• There are three known isotopes of Hydrogen.

H H H
2
1
3
1
1
1
1 proton 0 neutrons
1 proton 1 neutron
1 proton 2 neutrons
9
What do these numbers mean?
Mass Number

• Li

7
Element Symbol
3
Atomic Number
How many protons does lithium have? How many
neutrons does lithium have?
10
Atomic Mass

• The atomic mass is NOT the same as the mass
  number.
• The atomic mass shown on the periodic table is an
  average of all the isotopes of that element.