Atomic Theory Flashcards
What was Democritus’ theory?
- Matter can be broken down to particles, but particles can’t be broken down.
- Particles are called atomos.
What was Democritus’ experiment?
Split rock into half and saw it had same properties.
What was Democritus’ model of the atom?
Solid Sphere
What was Aristotle’s theory?
All matter was made of the following elements: Earth Air Fire Water
What was Franklin’s theory?
Electricity was composed of negatively charged particles.
Atoms usually have a _______ charge
Neutral
Where does the word electricity come from?
Elektron meant amber in Greek.
What was Dalton’s theory?
- Matter is composed of small particles called atoms.
- Atoms of a given element are the same size and shape, but differ from other atoms of different elements(FALSE, exception are isotopes).
- Atoms can’t be subdivided, created, nor destroyed(False, due to nuclear reactions).
- Atoms can combine to form compounds with whole number ratios(Law of Multiple Proportions). Compounds combine in whole number ratios.
- In chemical reactions atoms are combined, seperated, or rearranged.
What was Dalton’s model of the atom?
Solid Sphere that was indivisible
What did Dalton accept to make his five statements?
- Two elemets can combine to form a compound.
2. Pure substances of a compound have the same composition by mass.
What was JJ Thomson’s theory?
- If atoms are neutral, they must be positivily charged particle in the atom.
- If atoms have mass, there should be other particles with a greater mass.
- There is a particle in atom that is negativly charged.
- This particle has mass.
What was Thomson’s model of the atom?
Known as the Plum pudding Atom.
Majority/Center is positive, while electrons are on the outside scattered.
What was the significance of Thomson’s theory?
First discovery of a sub-atomic particle (electrons).
Who confirmed Thomson’s theory?
Robert Millikan, did the oil drop experiment, which showed how tiny the electron was compared to the whole atom.
What was JJ Thomson’s experiment?
Conducted two significant experiments.
Used a Cathode Ray Tube, Alpha Particles, Magnet, and Paddlewheel.
In the first experiment shot the electrons(later named electrons) straight, but after it hit the magnet, curved towards positive side, indicating the particle had a negative charge.
In second experiment shot electrons straight, and turned the paddlewheel indicating the particles had mass.
What was Rutherford’s theory?
- Most of the atom was empty space.
- The nucleus is small, dense, and positive.
- Proposed electrons moved around the nucleus like the planets do to the sun, which was later disproved.
What was Rutherford’s experiment?
Shot positive alpha particles towards gold foil, by using lead with a hole in it to direct the alpha particles.
Noticed that most of the alpha particles went through the gold foil, but some deflected at different angles, which indicated that most of the atom was empty space, and when the alpha particle did deflect it hit the nucleus.
What was Chadwick’s theory?
- Credited witht he discovery of the neutron.
What was Chadwick’s experiment?
Bombared Be with alpha particles which emitted an energetic stream of radiation.
What was Rutherford’s model of the atom?
Nucleus is in the center(proton), while the electrons orbit in a definite ring.
Why did it take so long to discover the neutron?
- Neutron has no charge.
2. Great Depression
What was Bohr’s theory?
- Placed each electron at a specfic energy level.
- Electrons moved in defintie orbits around the nucleus.
- The energy levels are located at a specific distance from the nucleus.
- Electrons are located in energy levels outside of the nucleus.
- There is no change in energy when electron is in an energy level.
- Ground State is when th electron(s) is at it’s lowest possible energy state (when e- is stable).
- Delta E (Change in Energy) occurs ehen the electron changes energy levels.
- Electron’s absorb energy to move to a higher energy level, and release/emmit energy to move to a lower energy level.
What was Bohr’s model of the atom?
- Placed each electron at a specfic energy level.
- Lowest energy level is closest to nucleus.
- Electrons can move between energy levels.
- Electrons will never be found in between energy levels..
- Electrons are attracted to the positive nucleus but remain in orbits that revolve around the center nucleus.
- The orbit shells are called Principle Energy Levels (PEL’s), and are the regions where an electron can be found outside of the nucleus.
Who created the Wave-Mechanical Model?
Erwin Schrodinger
What is another name for the Wave-Mechanical Model?
Electron Cloud
What does the Wave-Mechanical Model state?
- Propesed that paricles have a dual-wave particle nature
- Electrons don’t travel in perfect orbits around the nucleus due to quantum mechanics.
- Electrons exist in a 3-D region around the nucleus.
- The probable location of the electron is called an orbital.
- Impossible to determine the exact location of an electron.
- The probable location depends on how much energy the electron has.
List in chronological order, all significant people or theories whom contributed to atomic theory.
- Democritus
- Aristotle
- Franklin
- Dalton
- Thomson
- Rutherford
- Bohr
- Wave-Mechanical Model
- Chadwick
Ground State vs Excited State
- In excited state the average distance between the nucleus and electron increases.
- Ground State is when th electron(s) is at it’s lowest possible energy state (when e- is stable).
- Excited State occurs when energy is absorbed by the electron, which makes it move up in energy levels.
- Atomic Excitation is when the electron absorbs energy, while Atomic De-xcitation is when the electron releases/emitts energy.
- Electron only absorbs require amount of energy, no more, no less.
Proton
Neutron
Electron
Proton - p, 1 amu, +1
Neutron - n, 1 amu, 0
Electron - B- or e-, 1/1826 amu, -1
Units of measurement
amu - Atomic Mass Unit(Dalton)
1 amu - 1/12 mass of C-12
1 C atom - 12 amu
What is atomic number?
Number of protons
Number of protons = __________
Why?
Number of electrons because usually atoms are neutral(exception are ions).
What is Isotope Notation?
Base is the element.
Superscript is the atomic mass.
Subscript is the atomic number.
What are ions?
- Charged particles caused by gaining or losing electrons.
- The charge of the ion tells you the number of ions.
- Ions don’t change the identity of the element.
If charge is positive __________ to find the number of electrons.
Subtract the charge from the atomic number.
More protons than electons.
If charge is negative __________ to find the number of electrons.
Add the charge to the atomic number.
More electrons than protons.
Protons and Neutrons in the nucleus are particles known as __________.
Nucleons
The sum of the nucleons is the __________ of the atom.
Mass of the nucleus
To get mass number of an element __________.
Round the atomic mass.
The number of neutrons is the __________ - __________
Mass Number
Atomic Number
What is an Istope?
Atoms that have a different number of neutrons, therefore they have a different mass number compared to the other atoms of said element.
What are the three isotopes of Hydrogen?
How many nuetron(s) does each isotope have?
Protium - 1 proton (99.985% on Earth)
Deuterium (Heavy Water) - 1 proton and 1 neutron (0.015% on Earth)
Tritium - 1 proton and 2 neutrons (trace amounts found on Earth)
What is a nuclide?
The term for any isotope.
How to find Average Atomic Mass?
(Percent Abundance * Mass Number)/(100)
Sum the values to get Average Atomic Mass
*Don’t Divide!!!
What are the maximu number of electrons per (PEL)
1 - 2
2 - 8
3 - 8 for #1-20 and 18 for #21 and above
4- 32
What didn Bohr not know?
Why were only certain energies were allowed.
Called these allowed energy levels.
What is the Quantum Mechanical Model?
- Within each energy level, electrons occupy sublevels or atomic orbitals.
- The number of enrgy sublevels is the Principle Quantum number (n=1,2,3,4…).
- The sublevels are s,p,d,f…
- Each sublevel has differnt shapes. s is spherical, p has a dumbell shape, while d and f are complex.
How many electrons can fit in each Quantum Number(QN)?
1 - 2
2 - 8
3 - 18
4 - 32
How to do Orbital Configuration?
s - 1 box, hold max of 2 electrons
p - 3 box, hold max of 6 electrons
d - 5 box, hold max of 10 electrons
f - 7 boxes, hold max of 14 electrons
*Each orbital can hold a max of 2 electrons
*Make sure each box has one electron, before placing the second electron in the orbital.
What is Angular Momentum QN in relation to the sublevels?
s - l=0 p - l=1 d - l=2 f - l=3 *l related to the shpae of the orbital
What is Magnetic QN in relation to the sublevels?
s = 0 p = -1,0,1 d = -2,-1,0,1,2 f = -3,-2,-1,0,1,2,3 *m(l) relates to the orientatation of the orbital in space relative to the pther orbitals. *Pick only one number for an electron!!!
What is Electronic Spin QN in relation to the sublevels?
m(s) = +1/2 or -1/2
+ when arrow points up
- when arrow points down
What is the Aufbau Principle?
States that electrons enter the orbitals of the lowest energy first.
Start with n=1 then move from there.
What is Hund’s Rule?
States that when electrons occupy orbitals with equal energy, one electron must eneter each orbital, before adding a second electron to an orbital.
What is the Pauli Exclusion Principle?
States that no two electrons have identical values for their quantum numbers(n,l,m(l),m(s))
No more than two electrons can occupy the same orbital.
The two electrons in the same orbital must have opposite spins.
What is the definition of Quanta?
A specific, discrete amount of energy to move an electron from one energy level to the next (hv).
h is Plank’s constant(6.626210^-34)
v is frequency.
When the electron returns to a lower shell, it will emitt the same amount of enregy(photon(s)) due to the Law of Conservation.
What does a spectroscope do?
Lets you view how color is composed of different wavelengths.
What is the definition of a wavelength?
The distance between two crests in a wave.
Lambda is the symbol for wavelength.
What is the definition of a frequency?
Number of waves that pass a given point in space per second.
What is the speed of light?
2.9979*10^8 m/s
c is the symbol for the speed of light.
What kind of relationship is between Wavelength and Energy?
Inverse Relationship
What kind of relationship is between Frequency and Energy?
Direct Realtionship
What kind of relationship is between Wavelength and Frequency?
Inverse Relationship
What is E?
The energy of quanta(photons).
What is Planck’s constant?
6.6262*10^-34
What is Rydberg’s constant?
1.097*10^5
E(n) = -R/n^2
R is Rydberg’s constant.
n is the enrgy level.
Delta E = E(final) - E(initial)
Use E(n) = -R/n^2 to calculate E(final) and E(initial).
Electromagnetic Spectrum
Radio, Microwaves, Infrared, Visible Light, Ultraviolet, X-Ray, Gamma, and Cosmmic.
What are Emission Line Spectrums?
Contains only some of the wavelengths of light.
Each atom has its own disitnct pattern of emmision lines which represent different wavelengths(energy) being releases(emmitted) by the electron as it moves back to ground state from an excited state.
What are the Paschen series?
When the electron moves down to n=3.
What are the Balmer series?
When the electron moves down to n=2.
What are the Lyman series?
When the electron moves down to n=1.
What is the Emmision Spectrum?
Reperesents the energy released(emitted) as the electron moves to ground state from an excited state.
What is the Absorption Spectrum?
The opposite of the Emision Spectrum.
Reperesents the energy absorbed as the electron moves to an excited state from ground state.
Concern’s of Bohr’s Model
- Model didn’t explain why the electron stayed in orbits instead of colliding with a the positive nucleus.
- Couldn’t explain the spectral lines of any other element except hydrogen.
How many valance electrons in each group of the periodic table?
1 - 1 2 - 2 13 - 3 14 - 4 15 - 5 16 - 6 17 - 7 18 - 8
What are the Lewis Dot Structures?
Kernel - The nucleus and the inner electrons
Valence - Electrons located on the outermost PEL.
*Valence are most important electrons bcause they are involved with chemical reactions.
What are Valance Electrons?
They are electrons in the outermost shell (highest PEL).
Can be identified in the Bohr configuration.
Lewis Dot Rules
- Write the symbol of element.
- Determine the number of valence electrons.
- The first two dots go together, any side.
- Move counter - clockwise.
* After the first two electrons, put only one on each side, then you may put the second electron on each side.
* No more than eight valance electrons.
