1. The Nucleus
Chapter 14
Section 2

2. What is an Atom? Most basic units of matter
Everything in world made up of atoms
Air you breathe
Desk you are sitting in
Your body
Smallest particle of an element with all the properties of the element that can combine with other atoms to form a molecule

3. How many different types of Atoms are there?
92 naturally occurring atoms
25 synthetic atoms (made by scientists in laboratory)

4. What is an Element? Matter made of atoms of only one kind
Example: piece of aluminum foil
Element Aluminum—many of same kind of atom
Each atom has same properties: shiny, metal, flexible

5. Parts of the Atom Particle Charge Location Weight Proton Positive (+)
Nucleus
1 amu
Neutron
Neutral
(no charge)
Electron
Negative (-)
Electron cloud
0.018 amu
amu = atomic mass unit

6. Two-Dimension Model
Protons & neutrons placed together in center—nucleus
Electrons orbit nucleus in space called electron cloud
Electron cloud organized into energy levels
1st level—can hold 2 e-
2nd level—can hold 8 e-
3rd level—can hold 18 e-

7. Identifying Numbers
How does the nucleus in an atom of one element differ from the nucleus of an atom of another element?
Atoms of different elements contain different numbers of protons

8. Identifying Numbers
Atomic Number —number of protons in the nucleus of an atom
Hydrogen, smallest atom, has 1 proton
Uranium, heaviest natural atom, has 92 protons
atoms are identified by the number of protons
The number never changes without changing identity of element

9. Identifying Numbers
Isotopes –atoms of the same element that have different numbers of neutrons
element carbon has 6 protons (atomic number)
Isotopes of carbon can have 6, 7, or 8 neutrons
Mass number—number of neutrons plus the number of protons

10. Isotopes of Carbon
Carbon-12
Carbon-13
Carbon-14
Mass Number 12 13 14
# protons 6
# neutrons 7 8
# electrons
Atomic Number
Average atomic mass—average mass of the mixture of an element’s isotopes

11. Synthetic Elements
Elements that are made in labs by smashing atomic particles into a target element
Elements with atomic numbers 93 to 112, and 114 are synthetic elements