1. Distinguish Between Atoms
Chapter 5 Section 3

2. The structure of the atom
Amu = atomic mass unit
The atom has three subatomic particles
The protons (+ charge) and 1 amu
The neutrons (0 charge) and 1 amu
The electrons (- charge) and 0 amu
The protons and the neutrons are located in the center (nucleus) of the atom.
The electrons are moving around the nucleus.
All of the mass of the atom is located in the nucleus.

3. The Atomic Model of the Helium Atom
2 P +
2 N
1st shell e-
2 electrons
nucleus

4. Subatomic Particles Subparticle Charge Location in the atom Mass (amu)
Electrons
negative (-)
Around nucleus
0 amu
Protons
Positive (+)
Nucleus
1 amu
Neutrons
neutral (0)

5. Identifying Atoms
The Atoms in the periodic table
The atoms in the periodic table have a neutral charge.
Number of protons (+) = number of electrons (-)
An oxygen atom has 8 protons (+8) and 8 electrons (-8)
(+ 8) + (-8) = 0

6. Na 22.99 11 Atomic Number of an element.
It is the number of protons in the nucleus.
Atomic number = Number of protons
It is the number on top of the chemical symbol in the periodic table. 11 Na
22.99

7. The periodic table is organized by increasing atomic number.
Why atoms of one element are different from atoms of another element?
Atomic number = ID of an element
Atoms are different because they contain different number of protons (different atomic number).
All oxygen atoms have 8 protons in the nucleus.
All hydrogen atoms have 1 proton in the nucleus.
The periodic table is organized by increasing atomic number.

8. The nucleus of the atom has protons and neutrons.
How to find the number of neutrons of an atom
Mass number is the number of protons and neutrons in an atom.
Mass number is the rounded number under the chemical symbol.
Mass number = Number of protons +
Number of neutrons
Number neutrons = Mass number
- Atomic number

9. Atomic Number and Mass Number11 Na 23
Number of protons
Atomic Number
Sodium
Symbol
MASS NUMBER

10. Possible Test Question (PTQ)
How many protons does Zn have?
Assuming that the Zn atom is neutral, how many electrons does it have?
How many neutrons does Zn have if the mass number is 65? 30 Zn
65.39