Atomic and Nuclear Physics Atomic structure Atomic structure.
Atomic Structure
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Transcript of Atomic Structure
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
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
NucleusElectron
Cloud
The nucleus contains 2 of the 3 Subatomic Particles: Protons: positively (+) charged subatomic
particles Neutrons: neutrally ( ) charged subatomic
particles
The 3rd Subatomic Particle resides outside of the nucleus in the electron cloudElectron: the subatomic particle
with a negative charge and relatively no mass
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
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
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
http://www.videopediaworld.com/video/16322/Chemistry-of-Life-Atoms-and-Elements
http://www.videopediaworld.com/video/16322/Chemistry-of-Life-Atoms-and-Elements
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 #
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 = 20 - 10= 10
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
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
Pass out the student worksheet from “The Atoms Family” Lesson
Atomic Math Challengeat this time and complete in class
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 1st energy ring can hold up to 2 e-
The 2nd energy ring can hold up to 8 e-
The 3rd energy ring can hold up to 18 e-
The 4th energy ring and any after can hold up to 32 e-
Bohr Model Practice
Lithium
Atomic # 3
Atomic Mass 7
Protons 3
Neutrons 4
Electrons 3 # Electrons
1st energy ring / level 2
2d energy ring / level 1
3d energy ring / level
4th energy ring / level
P+ = 3
N = 4
Bohr Model Practice
Aluminum
Atomic #
Atomic Mass
Protons
Neutrons
Electrons
# Electrons
1st energy ring / level
2d energy ring / level
3d energy ring / level
4th energy ring / level
13
27
13
14
13
2
8
3none
P+ = 13
N = 14