• smallest part of element (pure substance) that has all the same properties of that element
– For example, if you take a lump of coal (the element carbon)
– break it into smaller and smaller pieces, the smallest piece that still acts like coal is one atom of carbon.

• 2 main parts
– nucleus
– electron cloud
Electron
Cloud
• Empty Space!

• Nucleus is the core of the atom
• Contains 2 subatomic particles:
– Protons
– Neutrons

Sub-atomic particle
• Charge = + (positive)
• Mass = 1 amu
* a tomic m ass u nit
• Location = nucleus
• Every atom of the same element has the same number of protons – example:
– All carbon atoms have 6 protons
– All Hydrogen atoms have 1 proton

How do we know how many protons there are in a single atom of an element?
• Use your periodic table!
• The atomic number tells you how many protons there are!
A

• Oxygen?
• Nickel?
• Hydrogen?
•2 protons in it’s nucleus?
•11 protons in it’s nucleus?
•5 protons in it’s nucleus?

• Do any two elements have the same number of protons? Why/why not?

Sub-atomic particle
• Charge = 0 (neutral)
• mass = 1 amu
a tomic m ass u nit
• Location = nucleus

How do we know how many neutrons there are in a single atom of an element?
• Use your periodic table!
First:
With your team, determine the number of protons in your assigned element and place them in the nucleus of your atom

Look at the atomic mass of your element and round it to the nearest whole number.
This number shows you how many TOTAL subatomic particles should be in the nucleus of your atom.
Iron has an atomic mass of 55.847 – this number rounds to
____???____.
A
Thought question:
How can you make your atom’s nucleus have the correct number of particles?

Protons + Neutrons = The atomic mass of an atom – all calculable mass is contained in the nucleus!
OR
The atomic mass (rounded) – atomic number (or protons)
= the number of neutrons!
How many neutrons does your element have?
Raise your hand when you are ready for me to check your work!
A

1. Which 2 subatomic particles are found in the nucleus and what are their electrical charges?
2. Using an element key, how can you determine the number of protons an element has?
3. Using an element key, how can you determine the number of neutrons an element has?
4. What is special about the number of protons an atom has?
5. Where is all of the mass found in an atom?