1. Atomic Structure Hmmmm… Imagine cutting a gold bar in half.
Then cut in half again.
…and again.
How small could you cut up that gold and it still be gold?

2. Atoms
An atom is the smallest particle into which an element can be divided and still be the same substance.
Atoms make up elements and elements combine to form compounds.

3. element – Substance made up
atom – The smallest particle that can
exist on its own.
element – Substance made up
of only one type of atom.
compound – Substance made up of two or more different elements that are chemically joined together.

4. Atoms An atom is made of 3 parts:
Protons (+)
Neutrons (neutral)
Electrons (-)
Protons and neutrons make up the nucleus of the atom
Electrons orbit around the nucleus like planets around the sun

5. Notice that the electrons are not apart of the nucleus
Subatomic Particles
Protons
Neutrons
Electrons
Nucleus
Notice that the electrons are not apart of the nucleus

6. Protons Positive Charge
Atomic Structure
Protons
Positive Charge
The number of protons determines which element it is.
All elements have different numbers of protons
1 amu
Composed of quarks

7. Rutherford’s Gold Foil Experiment 1919
In Rutherford’s gold foil experiment ( ),positively
charged particles
were aimed at atoms of gold.
mostly went straight through the atoms.
were deflected only occasionally.
Conclusion:
There must be a small, dense, positively charged nucleus in the atom that deflects positive particles that come close.
Rutherford proposed that the atom must consist mainly of empty space with the mass concentrated in a tiny central core—the nucleus

8. What makes one element different from another element?
Number of protons.
Atomic Structure

9. Neutron Neural charge Located in the nucleus 1 amu Composed of quarks
Atomic Structure
Neutron
Neural charge
Located in the nucleus
1 amu
Composed of quarks
Neutrons were discovered by James Chadwick in Have mass like proton, but no charge.

10. Electrons Smallest subatomic particle. 1/1800 the mass of a proton.
Atomic Structure
Electrons
Smallest subatomic particle.
1/1800 the mass of a proton.
Orbit nucleus.
Negative Charge

11. Discovery of the Electron-Thomson 1897

12. Electrons are found in different levels around the nucleus.
Atomic Structure
Electrons are found in different levels around the nucleus.
These are called Energy Levels or shells.
Each energy level also has “sublevels” or orbitals

13. Atomic Structure

15. Electrons are found in the surrounding the nucleus.
Atomic Structure
Electrons are found in the
Electron cloud
surrounding the nucleus.

16. Each Energy Level Can Hold A Certain Number of Electrons!
Atomic Structure
Each Energy Level Can Hold A Certain Number of Electrons!
Only TWO on the first level!

18. Atoms Activity: Use your notes to draw an atom and label its parts.
3 Protons (+)
3 Neutrons (neutral)
3 Electrons (-)
Nucleus
Your drawing should fill an entire page and it should be colored/shaded.

19. Atomic Structure

20. Atomic Structure

21. 1 Atomic Mass Sum of Protons & Neutrons Atomic Number
Atomic Structure
Atomic Number
Number of Protons 1 H
Atomic Mass
Sum of Protons & Neutrons 1
The # of Protons determines the identity of an element. All elements have different number of protons.

22. How can I find out how many electrons an atom has?
Atom= neutral
So, the number of protons = electrons.
Atomic number tells you the number of protons
So, it also tells you the number of electrons!
Atomic Structure

23. Isotopes

25. Isotopes
iso = same
atoms of the same element with different numbers of neutrons
have different atomic masses but the same atomic number
some are stable, some are radioactive (carbon-12 and carbon-14)

27. Most isotopes are stable but radioactive isotopes are unstable and break down into more stable forms by emitting particles and energy (radiation).
Radiation can be detected, so radioactive isotopes are useful as labels in scientific research and medical diagnostic procedures.

28. Let’s Do some practice problems 