1. The Atom
Grade 9 Science
Ms. Raper.

2. What is an Atom???
The word atom comes from the Greek word Atmos which means unable to be divided.
Democritus suggested that everything was made of tiny particles that could not be divided any further.
We now know that atoms can be split into smaller pieces.

4. Different Models of the Atom
John Dalton – the atom is like a billiard ball
Thompson – The atom is like a chocolate chip cookie.
Rutherford – the atom has a central nucleus with electrons around
Bohr – positive nucleus and then empty space where the negative electrons orbit

6. What does and Atom look like?
An atom has 2 main parts.
A nucleus
And orbits (shells)

7. The Nucleus Contains: Protons, these have a positive (+ve) charge
Neutrons, these have zero (0) charge.

8. Orbits (shells)
Orbiting the nucleus are negatively (-ve) charged particles called Electrons.
These electrons are held in their orbits because they are attracted by the +ve protons

9. Atoms are different…
Each element has its own unique number of Protons.
This identifies which element is which
Hydrogen has 1 proton
Carbon has 6.
This is called the atomic number (AN)

10. Each element has a place on the Periodic Table
This place depends on how many PROTONS are found in the nucleus of the atom
Protons give the atom MASS
1 proton has 1 mass weight.

11. Neutrons & Electrons Neutrons have no charge.
They have a mass of 1 mass unit
Electrons have a –ve charge.
2000 electrons weight the same as 1 proton
Proton
Neutron
Electron
Mass 1
1/2000
Charge
+ve
-ve

12. Atomic Number = Number of Protons
Atomic Mass = Number of protons and the number
of neutrons

14. Orbit
Proton
Nucleus
Neutron
Electron

15. Electron Arrangement
The orbits can only hold a certain number of electrons.
The first orbit closest to the nucleus can hold only 2 electrons
The second orbit can hold 8 electrons
The third orbit can hold 8 electrons

16. Number of electrons in Each Orbit.1 2 3 4
Total # of electrons able to fit in the orbit 8 18

17. Rules Atomic Number = 10 Atomic Mass = 20 Electrons = 10 2,8,0,0
The orbits must be filled in order.
First the orbit closest to the nucleus and then the next. And so on
Atomic Number = 10
Atomic Mass = 20
Electrons = 10
2,8,0,0
Element = ?

18. = # of protons & neutrons
Element #
Name
Symbol
Atomic Mass Number
= # of protons & neutrons
Atomic Number
= # of protons
Number of neutrons =
AMN - AN
Number of Electron
= number of protons
Electron Arrangement 1
Hydrogen H
1,0,0,0 2
Helium He 4
2,0,0,0 3
Lithium Li 6
2,1,0,0
Beryllium Be 9 5
2,2,0,0
Boron B 10
2,3,0,0
Carbon C 12
2,4,0,0 7
Nitrogen N 14
2,5,0,0 8
Oxygen O 16
2,6,0,0
Fluorine F 19
2,7,0,0
Neon Ne 20
2,8,0,0 11
Sodium Na 22
2,8,1,0

19. = # of protons & neutrons
Element #
Name
Symbol
Atomic Mass Number
= # of protons & neutrons
Atomic Number
= # of protons
Number of neutrons =
AMN - AN
Number of Electron
= number of protons
Electron Arrangement 12
Magnesium Mg 24
2,8,2,0 13
Aluminum Al 26
2,8,3,0 14
Silicon Si 28
2,8,4,0 15
Phosphorus P 30
2,8,5,0 16
Sulfur S 32
2,8,6,0, 17
Chlorine Cl 35 18
2,8,7,0
Argon Ar 39 20
2,8,8,0 19
Potassium K
2,8,8,1
Calcium Ca 40
2,8,8,2

20. What are these 3 Elements?

21. What are these 3 Elements?

22. P= N=