1. Atoms

2. What are atoms? All matter is made of atoms.
An atom is the smallest piece of an element. It is one million times smaller than the width of a piece of hair.
Each type of atom represents a different element on the Periodic Table.

3. Atoms Each atom is different because of the number of protons it has.
This is called the atomic number.
Atoms are arranged on the Periodic Table by their atomic number, or, by the number of protons in the nucleus.

4. What are the main sections of an atom. What are the parts of an atom
What are the main sections of an atom? What are the parts of an atom? Where can each part be found?
An atom has a nucleus in the center surrounded by the electron cloud.
An atom has three parts: protons, neutrons and electrons.
Protons and neutrons are found in the nucleus.
Electrons whiz around outside of the nucleus in the electron cloud.

5. Na Cl 11 17 Find the atomic numbers for
Sodium (Na) and for Chlorine (Cl).
Na Cl
What do these numbers represent?
The number of protons!

6. Sodium – soft, silver metal that can be cut with a butter knife and explodes when in contact with water
Chlorine – pale, green, poisonous gas that was used in chemical warfare in the past

7. Does an atom have mass?
Atoms are so small that their mass is measured in atomic mass units, amu.
Each proton is 1 amu.
Each neutron is 1 amu.
An electron is 0 amu.
Where is most of the mass of an atom?
0 amu
1 amu
1 amu

8. Atomic Mass The mass of an atom is in its nucleus.
The mass is equal to the number of protons and neutrons.
Protons + Neutrons = Atomic Mass
The unit for atomic mass is the atomic mass unit.

9. Atomic Mass
The number of neutrons in an atom is not given on the Periodic Table.
To determine the number of neutrons you round the atomic mass and subtract the atomic number.

10. Atomic Mass rounded atomic mass – atomic number = number of neutrons
(protons + neutrons) – protons = neutrons

11. Atomic Mass
Examples
Sodium, Na, is atomic #11 and has a mass of amu
23 – 11 = 12 neutrons
Chlorine, Cl, is atomic #17 and has a mass of amu
35 – 17 = 18 neutrons

12. Na has 11 protons and 12 neutrons. What is its atomic mass?
Cl has 17 protons and 18 neutrons. What is its atomic mass?
23 amu 35 amu

13. Does an atom have charges?
Protons are positive (+)
Neutrons are neutral (0)
Electrons are negative (-)
Is the nucleus charged?
Is the electron cloud charged? - +

14. Does an atom have charges?
Protons are positive (+)
Neutrons are neutral (0)
Electrons are negative (-)
The nucleus is positive.
The electron cloud is negative.
Because an atom has the same number of + protons and - electrons, an atom is neutral. - +

15. Electron Clouds
The electron cloud is the area surrounding the nucleus. The electrons whiz around here.
Most of the area is empty space!
Electrons are arranged in shells (orbitals) in energy levels called shells.
The shell farthest from the nucleus is called the valence orbital. The electrons here have the most energy.
When the shell is full, it is said to be complete.

16. Electron Configuration
Electrons fit into the shells around a nucleus in an arrangement called the electron configuration.
Electrons farther from the nucleus are called valence electrons. They have more energy.

17. Electron Configuration
Example: Sodium (Na) has an electron configuration of
2 electrons in K shell
8 electrons in L shell
1 electron in M shell

18. Electron Configuration
Example: Chlorine (Cl) has an electron configuration of
2 electrons in K shell
8 electrons in L shell
7 electrons in M shell

19. Electron Configuration
What happens when you add the numbers in the electron configuration?
Na = 11
Cl = 17

20. Electron Configuration
K shell – closest to nucleus, holds 2 electrons
L shell – holds up to 8 electrons
M shell – holds up to 8 or up to18 electrons
There are also N, O, P and Q shells for a maximum of 7 energy levels.
Look at your valence electrons. Are you complete?

21. Are the shells “complete”? Sodium:
2 electrons in K shell
full
8 electrons in L shell
1 electron in M shell
not full
Since this last shell
is not full, the atom is
not complete!

22. Are the shells “complete”? Chlorine
2 electrons in K shell
full
8 electrons in L shell
7 electrons in M shell
not full
Since this last shell
is not full, this atom
Is not complete!

23. Valence Electrons
Electrons in the shell farthest from the nucleus are called valence electrons.
These electrons form chemical bonds with other atoms and give elements their chemical properties.
Atoms combine with other atoms to complete their outermost or last energy level to become more stable.

24. How many valence electrons do you have?
Na has 1 Cl has 7

25. Na has 1 valence electron. Cl has 7 valence electrons.
Write Na on your board. Write Cl on your board.
Draw one dot to the right of Draw two dots to the left,
the symbol. two dots on top, two dots on
the bottom, and one dot to the right of the symbol.
Lewis Dot Structures

26. Chlorine, what do you want more than anything in the whole wide world?

27. Sodium, you are in danger!
Why?

28. More on Atoms
Because atoms have the same number of positive protons and negative electrons, atoms are neutral. They have no charge.
If an atom loses or gains electrons, it is called an ion.
An ion is a charged particle.

29. Ions
If an atom loses an electron (-), would it be a positive or negative ion?

30. Ions
If an atom loses an electron (-), would it be a positive or negative ion?
Positive because you are taking away a negative charge so there are more protons than electrons
Example: Sodium has 11 protons and 11 electrons. If it loses an electron, it has 11 positive protons but only 10 negative electrons.

32. Ions
If an atom gains an electron (-), would it be a positive or negative ion?

33. Ions
If an atom gains an electron (-), would it be a positive or negative ion?
Negative because you are adding a negative charge so there are more electrons than protons
Example: Chlorine has 17 protons and 17 electrons. With an additional electron, chlorine has 17 positive protons and 18 negative electrons.

34. Chlorine, add an electron to your Lewis Dot Structure.
What type of ion are you? Draw that sign on your board.
Sodium, erase your electron from your Lewis Dot Structure.

35. What happens to opposites?

36. When atoms bond, they create a new substance. Na + Cl → ?