This document discusses the structure of atoms. It explains that atoms are made up of a nucleus containing protons and neutrons, surrounded by an electron cloud containing electrons. The atomic number is the number of protons, which determines the element. The mass number is the total number of protons and neutrons. Examples are provided to demonstrate how to determine the atomic number and mass of different elements using their nuclear symbols or the periodic table.

1. Atomic Structure
Atomic Number and Atomic Mass

2. Structure of the Atom
• Atom – smallest particle of an element that can exist
alone
– Two regions of an atom
• Nucleus
– Center of atom
– Protons and neutrons
• Electron “cloud”
– Area surrounding nucleus
containing electrons

3. Structure of the Atom
• Proton – Positive charge (+), 1 atomic mass unit (amu);
found in the nucleus
– amu -Approximate mass of a proton or a neutron
• Neutron – Neutral charge (0), 1 amu; found in the
nucleus
• Electron – Negative charge (-), mass is VERY small

4. • Atomic Number
– Number of protons in nucleus
– The number of protons determines identity of the element!!
• Mass Number (Atomic Mass)
– Number of protons + neutrons
– Units are g/mol

5. – Nuclear Symbol Notation

6. Find out the Atomic number and Atomic
Mass of Sulfur using the given Atomic
model.

7. Atomic Number= 16
(Since it has 16 protons in the Nucleus)
Atomic Number = 16+16 = 32
( Since 16 proton and 16 neutrons are
present in the nucleus)
16 Electrons are present in shells of
Sulfur

8. Let complete the given
information
Aluminum (Al)
Protons = 13
Electrons =
Neutrons = 14
Atomic Number =
Atomic Mass =
Let complete the given
information
Aluminum (Al)
Protons = 13
Electrons = 13
Neutrons = 14
Atomic Number = 13
Atomic Mass = 13+14= 27

9. • Nuclear Symbol notation (no
periodic table)
– Protons =
– Electrons =
– Neutrons =
– Atomic Number =
– Atomic Mass =
A
g
108
47

10. • Nuclear Symbol notation (no
periodic table)
– Protons = 47
– Electrons = 47
– Neutrons = 108-47=61
– Atomic Number = 47
– Atomic Mass = 108
A
g
108
47

11. • use the periodic table
– Protons =
– Electrons =
– Neutrons =
– Atomic Number =
– Atomic Mass =
Uranium-235

12. • use the periodic table
– Protons = 92
– Electrons = 92
– Neutrons = 235-92= 143
– Atomic Number = 92
– Atomic Mass = 235
Uranium-235

13. Use the periodic table
– Charge =
– Protons =
– Electrons =
– Neutrons =
– Atomic Number =
– Atomic Mass =
K
39 1+

14. Use the periodic table
– Charge = +1
– Protons = 19
– Electrons = 18
– Neutrons = 39-19=20
– Atomic Number = 19
– Atomic Mass = 39
K
39 1+