1. Matter & The Atom

2. Matter
The term matter describes all of the physical substances around us: your table, your body, a pencil, water, and so forth

3. Matter Anything that has mass and takes up space (has volume)
Made up of different kinds of atoms

4. Matter is made of atoms

5. Definition of an Atom
the smallest component of an element having the chemical properties of the element

6. Definition of an Element
a substance that cannot be broken down into other substances by chemical or physical means

7. Atomic Structure
Nucleus
Protons
Neutrons
Electrons

8. Atomic Structure

9. Atomic Structure Electrons Tiny, very light particles
Have a negative electrical charge (-)
Move around the outside of the nucleus

10. Atomic Structure Protons Much larger and heavier than electrons
Protons have a positive charge (+)
Located in the nucleus of the atom 

11. Atomic Structure Neutrons Large and heavy like protons
Neutrons have no electrical charge
Located in the nucleus of the atom 

12. Describing Atoms Atomic Number = number of protons
In a neutral atom, the # of protons = the # of electrons

13. Describing Atoms
Atomic Mass Number - equal to the number of protons plus neutrons.

14. Ions An atom that carries an electrical charge is called an ion
If an atom gains electrons, the atom becomes negatively charged (more negative charges than positive charges)
If it loses an electron, it becomes positively charged

15. Ions (cont.) The number of protons does not change in an ion
The number of neutrons does not change in an ions
So, both the atomic number and the atomic mass remain the same.

16. Ions
This atom has lost an electron. Now it has one more proton than electron.
One more proton means one more positive charge.
This makes the total charge of the atom POSITIVE.
This atom has gained an electron. Now it has one less proton than electron.
One less proton means one less positive charge.
This makes the total charge of the atom NEGATIVE.

17. Isotopes The number of protons for a given atom never changes.
The number of neutrons can change. 
Two atoms with different numbers of neutrons are called isotopes

18. Isotopes (cont.) Have the same atomic number (number of protons)
Have different atomic mass numbers (number of protons + neutrons)

19. Isotopes

20. Models
In the case of atoms, scientists use large models to explain something that is very small
Models of the atom were used to explain data or facts that were gathered experimentally.
So, these models are also theories

21. Models of the Atom Bohr
Electrons move in definite orbits around the nucleus

22. Modern Model of the Atom The electron cloud
Sometimes called the wave model
Spherical cloud of varying density
Varying density shows where an electron is more or less likely to be