Bohr’s Model
Bohr’s Model
• Niels Bohr (1885-1962)- Danish physicist and a student of Rutheford’s.
• 1913- changed Rutheford’s model to include new
discoveries about how the energy of an atom changes when it absorbs and omits light.
Bohr’s Model
• Each possible electron orbit in Bohr’s model has a fixed
energy.
• Energy Levels: fixed energy of an electron.
– Like rungs of a ladder – The lowest rung = lowest
energy level, which is closest to the nucleus.
Bohr’s Model
• A Quantum of energy is the amount of energy required to move an
electron from one energy level to another.
• The energy levels of electrons are labeled by principal quantum
numbers (n). • n= 1, 2, 3, 4…
Always fill the energy levels with electrons starting closest to the nucleus. 1 2 2 8 3 18 4 32 Energy Level (n) Maximum # electrons
Let’s Try One!
Electron Placement Activity!
• Periodic Table • Packet
Where Bohr was wrong…
Quantum Mechanical Model
• In 1926 Erwin
Schrodinger used a
mathematical equation to describe the behavior of the electron in a
hydrogen atom.
• Quantum mechanical model: describes
electrons in atoms based on Schrodinger’s
Quantum Mechanical Model
• Like the Bohr model, the quantum mechanical model restricts the energy of
electrons to certain values.
• However, it does not involve an exact path that an electron takes around a nucleus.
• The quantum mechanical
Electrons and
Probability
• How likely it is to find the electron in a particular location is described by probability.
• Simile: Blades on a plane • The probability of finding
an electron within a
Atomic Orbitals
• For each principal energy level, there are many
sublevels.
• Each energy sublevel
corresponds to an orbital of a different shape, which
describes where the electron is likely to be found.
• Quantum Mechanics • http://www.teachersdo
main.org/asset/phy03 _vid_quantum/
Electron Configurations!
• Aufbau Principle- electrons occupy the orbitals of lowest energy first (closest to nucleus)
• Pauli Exclusion Principle- each orbital may hold up to 2 electrons, with opposite spins.
• Hund’s Rule- electrons occupy orbitals of the same energy in a way that makes the number of electrons with the same spin direction as large as possible.
• Beryllium • Nitrogen • Fluorine • Aluminum • Argon • Calcium • Chromium
Aufbau Principle- electrons occupy the orbitals of lowest energy first (closest to nucleus)
Pauli Exclusion Principle- each orbital may hold up top 2 electrons, with opposite spins.
BINGO!
• Li • Na • Be • He • B • O • N • F • Mg • Al • Si • P • S • Cl • H • Sc • TiIn Bohr’s model of the atom, where
are the electrons and protons?
a. The electrons move around the protons, which are at the center of the atom
b. The electrons and protons move throughout the atom
c. The electrons occupy fixed orbits around the protons, which are at the center of the atom. d. The electrons and protons are located
Which is NOT true for the Bohr
model?
• A. electrons can jump to higher energy
levels if they receive the correct amount of energy
• B. The electrons circle the nucleus in orbits
• C. Electrons may occupy regions of space between the circular orbits
• D. When electrons jump to a lower energy level, they release energy in the form of
• The principal quantum number indicated what property of an electron?
a. Position b. Speed
c. Energy level
What letter identifies the principle
quantum number (aka energy level)?
• The smallest particle of an element that retains the properties of that element is a(n)
• A. atom
• The subatomic particles of an atom are • A. Protons and neutrons
• B. Protons and electrons • C. Electrons and Neutrons
• What two particles are in the nucleus? • A. protons and electrons
• What is the charge of an electron? • A. Negative
• What was Rutheford’s model of the atom? • A. A dense sphere with no charge
• B. A tiny sphere with negative charged particles throughout
• Dalton thought the atom was a
• A. tiny, dense sphere with no charge
• B. A tiny sphere with negatively charged particles throughout
• J.J. Thompson discovered the electron with the use of the
• A. Gold Foil experiment • B. Cathode Ray Tube
All atoms are
•A. positively charged, the number of protons exceeding the number of electrons
•B. negatively charged, with the number of electrons exceeding the number of protons
•C. neutral, with the number of protons equaling the number of electrons
A theory is
• A. proposed explanation for an observation
• B. well tested explanation for a broad set of observations
• C. summary of the results of many observations
Which of the following is NOT a
physical property
• A. mass • B. color
When a substance forms a vapor,
what physical state was it before?
• A. gas • B. liquid • C. solid
What state of matter has no definite
shape or volume?
• A. solid • B. Liquid • C. Gas
Which state has a definite volume
but no definite shape?
• A. gas • B. Solid • C. Liquid
Which state of matter has both a
definite shape and definite volume?
• A. solid • B. Liquid • C. Gas
What is another word for a
homogeneous solution?
• A. Solutions
• B. Homozygous mixture • C. Mixture
Which of the following is an
example of a homogeneous
mixture?
• A. Oil and water
• B. Rubbing alcohol
Which is true for compounds?
• A. They can be physically separated • B. They have compounds that vary • C. They are substances (aka pure
substances)
Which of the following is a chemical
property?
• A. hardness • B. Color
• C. melting point
When metal rusts, it is evidence of
a
• A. Physical change • B. Chemical change
What is the difference between a
mixture and a substance (aka pure
substance)
• A. substance are compounds, mixtures are not
• B. Mixtures are groups of elements and compounds arent
• C. Sample of the same substance have different properties
Quick Review
• In scientific method:
• Another word for independent variable is manipulated variable.
• Another word for dependent variable is
The variable that is observed
during an experiment is called what
type of variable?
• A. independent • B. manipulated • C. control
All of these are examples are
physical changes EXCEPT:
During a chemical reaction
• A. matter is neither created nor destroyed • B. some matter is destroyed
• C. some matter is created
The number 2012 in scientific
notation is
In the measurement 0.709ml, which
digit is the least precise?
• A. 7 • B. 0 • C. 9
In the measurement, .6745g, which
number is the estimated digit?
When a measurement is close to
the correct value, it has good
• A. Precision • B. Accuracy • C. Usefulness
The closeness of your
measurement to those of your lab
partners indicates
• A. accuracy • B. precision
