1. The Modern View of Atomic Structure
Section 2.3
The Modern View of Atomic Structure

2. Three Subatomic Particles
Proton
Neutron
Electron

3. Proton Positively charged particle Located in the nucleus of the atom
Charge of x C
Expressed in multiples of the charge= +1

4. Electron Negatively charged particle Orbit the nucleus of the atom
Account for most of the volume of the atom
Charge of x C
Expressed in multiples of the charge = -1

5. Neutron Uncharged and electrically neutral particle
Located in the nucleus of the atom

6. The Atom

8. Every atom has an equal number of protons and electrons, and so atoms have no net electrical charge.

9. Mass of the Atom Expressed in the atomic mass unit (amu)
1 amu = x g
1 g = x 1023 amu

10. Particle Charge Mass (amu)
Proton
Positive (+1)
1.0073
Neutron
None (neutral)
1.0087
Electron
Negative (-1)
5.486 x 10-4

11. Atomic Number
References the number of protons in the nucleus of an atom of a particular element
Every element has a unique atomic number

13. Question
If Pb has an atomic number of 82, how many protons are in the nucleus of every atom of Pb?
How many electrons must be orbiting the nucleus of every Pb atom?

14. Mass Number
Total number of protons plus neutrons in the nucleus of an atom of an element.
Uses the number of neutrons in the most abundant form of the element

15. How many protons?
How many electrons?
How many neutrons?

16. Isotopes
Atoms with identical atomic numbers but different mass numbers