1. Matter and Atoms ____________ are smallest parts of matter. ATOMS
The positively charged center of an atom is called a ____________
NUCLEUS
The nucleus is surrounded by negatively charged particles called _________.
ELECTRONS
The three particles that make up an atom are:
PROTONS, NEUTRONS and ELECTRONS

2. Matter and Atoms **These particles are called SUBATOMIC PARTICLES**
Mass of Particle
Charge
Location in the atom
Proton 1 +
In Nucleus
Neutron
None
Electron -
Outside Nucleus

3. Matter and Atoms
What is the charge of the NUCLEUS in at atom? (circle one)
POSITIVE
Label the following diagram of an atom:
Electron Nucleus
(outside nucleus) (central part)
Proton Neutron
(makes up nucleus) (makes up nucleus)

4. Counting Atoms What does the atomic number of the atom tell you?
Number of protons in nucleus
Number of electrons outside nucleus
a. How many protons and electrons does the element copper have? 29
b. How many protons and electrons does the element iron have? 26

5. Counting Atoms
*** THE NUMBER OF PROTONS IN THE NUCLEUS OF AN ATOM AND THE NUMBER OF ELECTRONS AROUND THE NUCLEUS DETERMINES WHAT THE ELEMENT IS. FOR EXAMPLE, THE ELEMENT HYDROGEN AND ONLY THE ELEMENT HYDROGEN WILL HAVE 1 PROTON AND 1 ELECTRON***

6. Counting Atoms
If the element Carbon (C) has the atomic number of 6, how many protons does it have ____________. How many electrons ____________.
6 protons
6 electrons
***THE NUMBER OF ELECTRONS = THE NUMBER OF PROTONS***

7. Counting Atoms Refer to your periodic table. Atomic Number 2 He 4.002
Symbol
Atomic Mass
Using the information above and your periodic table to answer the following questions:
a. What is the atomic number of Aluminum (Al)? 13
b. How many protons does (Ne) have? 10
c. How many electrons does Helium (He) have? 2
d. What is the atomic number of Einsteinium (Es)? 99
e. How many protons does Calcium (Ca) have? 20
f. How many electrons does Phosphorus (P) have? 15 2 He
4.002

8. The Atom: A Cloudy View
*An electron cloud is a region where electrons are most probably found. The electron cloud surrounds the nucleus of an atom.

9. Energy Levels and Electrons
Within the electron cloud, electrons are at various distances from the nucleus.
Electrons close to the nucleus have LOW energy
Electrons farther away from the nucleus have HIGHER energy.
What are the MAXIMUM electrons in each energy level?
a. 1st energy level
2 electrons
b. 2nd energy level
8 electrons
c. 3rd energy level
18 electrons
d. 4th energy level
32 electrons
e. 5th energy level
f. 6th energy level
g. 7th energy level
h. 8th energy level
Electrons with LOW energy
Electrons with HIGHER energy

10. Mass of Atoms
**ATOMIC MASS: the average mass of all the isotopes of that particular element.
**The atomic mass of Helium (He) is If you round it to the nearest whole number that would be the MASS NUMBER. So the mass number of Helium is 4. 2 He
4.002
Atomic Mass

11. Use your periodic table to determine the following:
What is the atomic mass of Oxygen (O)?
16.00
What is the mass number of Oxygen (O)? 16
What is the atomic mass of Nitrogen (N)?
14.01
What is the mass number of Nitrogen (N)? 14

12. Mass Number
The sum of the number of protons (atomic number) and the number of neutrons in an atom is called the MASS NUMBER. OR
Mass Number = Number of Protons (Atomic Number) + Number of Neutrons
What is the mass number of an element with 8 protons and 6 neutrons? 14
How many neutrons are in an atom with a mass number of 19 and 9 protons? 10

13. Use your periodic table for the following:
What is the atomic number of Magnesium (Mg)? 12
What is the mass number of Mg? 24
How many protons are in Mg?
How many neutrons are in Mg?
How many electrons are in Mg?

14. Isotopes of an Element
The definition of an isotope is atoms of the same element that have different numbers of neutrons.
Why isn’t the atomic mass of an element a whole number?
It is the average mass of an element of its isotopes.
How are isotopes of an element alike and how are they different?
The number of neutrons and mass number are different. The element name, symbol and atomic number are the same.

15. Isotopes of an Element Example of isotope:
Potassium (K) has the atomic number of 19. This will never change. However, there are situations where Potassium could have an atomic mass of (equals mass number of 39 and 20 neutrons). Potassium could also have an atomic mass of (equals mass number of 40 and 21 neutrons). Whenever you have an element that has at least two different values of neutrons, you have what is called an ISOTOPE.