1. Atomic Structure
Unit 4: Ch 4.2, 20.1, , 4
Geo Ch

2. Reading the Periodic Table
Element name
Atomic #
Symbol
Atomic mass

3. Practice - Label this own on your own!
Element
Atomic #
Symbol
Atomic mass

4. What are different ways of identifying atoms?
Atomic Number: Equal to the number of protons (+)
Examples:
H = 1
C = 6
O = 8

5. What are different ways of identifying atoms?
Mass Number:
Unit of measurement = amu (atomic mass unit)
1 proton = 1 amu
1 neutron = 1 amu
1 electron = 0 amu (too light to count)
Reminder: Round to the closest whole number
Atomic Mass:
Another way to talk about mass
The average of the isotopes found in nature.

6. What are different ways of identifying atoms?
MASS NUMBER = PROTONS + NEUTRONS or NEUTRONS = MASS NUMBER – ATOMIC NUMBER Example: How many neutrons are in U-236?
Neutrons = 236 – 92 = 144 neutrons

7. Determining Charge
Electron =
negative
Proton = -3
positive =0

8. Practice – Determine charge on your own!1+

9. Ions The previous example had a charge
An atom that has a charge is called an ion
A positive ion = cation
A negative ion = anion

10. Ion Symbols Atomic number (protons) = 3 Charge = +3 + -2 = +1
Element symbol = Li
Ion symbol = Li+

11. Practice – Write ion symbol on your own!
Cl1-

12. Making Ions Changing number of neutrons = changing mass number
Changing number of protons = changing atomic number = different element
Changing number of electrons = making atom charge = ION!

13. Isotopes
Atoms of the same element do not always have the same number of neutrons
These are called isotopes
The atomic number (number of protons) DOES NOT change
The mass number (protons plus neutrons) DOES change
Mass number
Atomic number

14. Isotope Symbols
A – mass number
Z – atomic number
X – element symbol

15. Isotope Symbols What is the element symbol?
What is the name of the element (find on periodic table)?
What is the atomic number?
What is the mass number?
How many protons does this element have?
How many neutrons does this element have? Li
Lithium 3 7 4

16. Practice- Answer these questions on your own!
What is the element symbol?
What is the name of the element (find on periodic table)?
What is the atomic number?
What is the mass number?
How many protons does this element have?
How many neutrons does this element have? Ti
Titanium 22 48 26

17. Warm-Up Fill in the missing information: Element Atomic Symbol
Number of Protons
Number of Neutrons
Number of Electrons
Mass Number
Atomic Number
Isotope Symbol
Boron
Oxygen 18 B 5
Element
Atomic Symbol
Number of Protons
Number of Electrons
Atomic Number
Ion
Symbol
N-3
Boron, B, 5, 6, 5, 11, 5, B-11
Oxygen, O, 8, 10, 8, 18, 8, O-18
Nitrogen, N, 7, 10, 7, N3-

18. What holds the atom together?
Forces Resource 1
Forces Resource 2
Physical Science, pages

19. 1. Electric Force Can be positive (protons) or negative (electrons)
Opposites attract, likes repel
To become positively charged, atoms must ____ electrons.
To become negatively charged, atoms must ____ electrons.
Charge, force, distance relationship  Coulomb’s Law

21. 2. Strong Nuclear Force
Strong Nuclear force holds the nucleus together.
Doesn’t depend on charge
Short range
Strong! 100x stronger than electric force
Small vs. Large Nuclei
Small – fewer p  sm electric force, same strong nuclear force, more tightly held together
Large – more p  lg electric force, same strong nuclear force, less tightly held together, more likely to be unstable (radioactive)
Radioactive  decay vs. induced fission