History of Atomic Theory
What were Democritus' contributions to atomic theory?
What are the three sub-atomic particles and where are they located?
Electrons --> orbitals around nucleus
Protons --> Nucleus
Neutrons --> Nucleus
What does atomic number tell us about an atom?
Number of protons and electrons
Hydrogen
1
What is an isotope?
Variations of an element's atoms based on the number of neutrons.
What was James Chadwick's contribution to atomic theory?
"Jimmy Neutron" discovered the neutron.
What does the number of protons determine?
Type of element
How can you decipher the number of neutrons in an atom?
Mass number - atomic number = # or neutrons
Oxygen
2, 6
What is mass number?
The amount of protons and neutrons in a specific atom or isotope.
Describe Thomson's atomic model.
"Plum Pudding Model" had negative electrons floating in a positively charged medium.
How can you figure out the number of electrons in an atom?
Same as the number of protons (in a neutral atom)
How many neutrons are in cadmium?
64 neutrons
Neon
2, 8
What is atomic mass?
The average mass of all isotopes of an element based on their abundance in nature.
Describe Rutherford's experiment and summarize its conclusions.
What is the purpose of neutrons?
To buffer protons so they do not repel each other
What do periods and groups tell us about the atoms within them?
Period --> number of orbitals
Group --> number of valence electrons
Sulfur
2, 8, 6
How do you calculate the number of neutrons by using the periodic table?
Subtract the atomic number from the rounded atomic mass.
Describe the current model of the atomic.
Electron cloud model:
1. Electrons move randomly in their orbitals.
2. No way to know precisely where an electron is at any point.
3. Denser the cloud, higher probability of finding an electron there.
How is energy related to location of orbitals?
Which elements have similar properties to boron?
All elements in group 13
Calcium
2, 8, 8, 2
DAILY DOUBLE: Calculate the atomic mass of neon if the isotopes have the following abundance:
Neon-20 --> 90.48%
Neon-21 --> 0.27%
Neon-22 --> 9.25%
N-20 --> 18.096
N-21 --> .0567
N-22 --> 2.035
Atomic Mass = 20.188