1. Science Virtual Friday, April 11 Ms. Kaufman
Atomic Structure
Science Virtual
Friday, April 11
Ms. Kaufman

2. What is an atom?
Atom: the smallest unit of matter that retains the identity of the substance
First proposed by
Democritus around
420 B.C.
“Atomos” in Greek
means indivisible

3. Atomic Structure Atoms are composed of 2 regions:
Nucleus: the center of the atom that contains the mass of the atom
Electron cloud: region that surrounds the nucleus that contains most of the space in the atom
Nucleus
Electron
Cloud

4. What’s in the Nucleus?
The nucleus contains 2 of the 3 Subatomic Particles:
Protons: positively (+) charged subatomic particles
Neutrons: neutrally ( ) charged subatomic particles

5. What’s in the Electron Cloud?
The 3rd Subatomic Particle resides outside of the nucleus in the electron cloud
Electron: the subatomic particle with a negative charge and relatively no mass

7. How do these particles interact?
Protons and neutrons live compacted in the tiny positively charged nucleus accounting for more than 99% of the mass of the atom
The negatively charged electrons are small and have a relatively small mass but occupy a large volume of space outside the nucleus

8. How do the subatomic particles balance each other?
In an atom:
The # of protons = the # of electrons
If 20 protons are present in an atom then 20 electrons are there to balance the overall charge of the atom—atoms are neutral
The neutrons have no charge; therefore they do not have to equal the number of protons or electrons

9. O Oxygen 8 15.99 Atomic Number Element Symbol Element Name Atomic Mass
Atomic Math Challenge 8
Atomic Number O
Element Symbol
Oxygen
Element Name
15.99
Atomic Mass

10. How do we know the number of subatomic particles in an atom?
Atomic number: this number indicates the number of protons in an atom
Ex: Hydrogen’s atomic number is 1
So hydrogen has 1 proton
Ex: Carbon’s atomic number is 6
So carbon has 6 protons
**The number of protons identifies the atom.
Ex. 2 protons = He, 29 protons = Cu

11. How do we know the number of subatomic particles in an atom?
Mass number: the number of protons and neutrons in the nucleus
Ex: Hydrogen can have a mass of 3.
Since it has 1 proton it must have 2 neutrons
# of neutrons = mass # - atomic #

12. Determining the number of protons and neutrons
Li has a mass number of 7 and an atomic number of 3
Protons = 3 (same as atomic #)
Neutrons= 7-3 = 4 (mass # - atomic #)
Ne has a mass number of 20 and an atomic number of 10
Protons = 10
Neutrons = = 10

13. What about the electrons?
The electrons are equal to the number of protons
So e- = p+ = atomic #
Ex: He has a mass # of 4 and an atomic # of 2
p+ = 2
no = 2
e- = 2

14. Determine the number of subatomic particles in the following:
Cl has a mass # of 35 and an atomic # of 17
p+ = 17, no = 18, e- = 17
K has a mass # of 39 and an atomic # of 19
P+ = 19, no = 20 e- = 19

16. Pass out the student worksheet from “The Atoms Family” Lesson
Atomic Math Challenge
at this time and complete in class

17. How exactly are the particles arranged?
Bohr Model of the atom:
Reviewers think this could lead to misconceptions!
All of the protons p+ and neutrons n are within the nucleus
The 3rd energy ring can hold up to 18 e-
The 1st energy ring can hold up to 2 e-
The 4th energy ring and any after can hold up to 32 e-
The 2nd energy ring can hold up to 8 e-

18. What does carbon look like?
Mass # = 12 atomic # = 6 p+ = 6 no = 6 e- = 6
6 p and 6 n live in the nucleus

19. Bohr Model Practice Lithium Atomic # 3 Atomic Mass 7 Protons 3
Neutrons 4
Electrons 3
P+ = 3
N = 4
# Electrons
1st energy ring / level
2d energy ring / level
3d energy ring / level
4th energy ring / level

20. Bohr Model Practice Aluminum Atomic # Atomic Mass 13 Protons Neutrons
Electrons 13 27 13
P+ = 13
N = 14 14 13
# Electrons
1st energy ring / level
2d energy ring / level
3d energy ring / level
4th energy ring / level 2 8 3
none

21. Hand out the Bohr Model Practice worksheet and assign 8 different atoms for students to complete their models