Chapter 9: Electrons in Atoms and the Periodic Table
Date:____________
Section 2: Quantum Theory and the Atom - Notes
Objectives:
 Compare the Bohr and quantum mechanical models of the atom.
 Explain the impact of de Broglie’s wave particle duality and the Heisenberg uncertainty principle
on the current view of electrons in atoms.
 Identify the relationships among a hydrogen atom’s energy levels, sublevels, and atomic
orbitals.
Bohr’s Model of the Atom:

Einstein’s theory of light’s dual nature accounted for several unexplainable phenomena, but it
did not explain why _____________________________________________________________
______________________________________________________________________________.

In 1913, ___________________________, a Danish physicist working in Rutherford’s laboratory,
proposed a quantum model for the hydrogen atom that seemed to answer this question.
o
This model correctly predicted the frequency lines in ____________________________
atomic emission spectrum.

o
The lowest allowable energy state of an atom is called its ________________________.
o
When an atom gains energy, it is in an ________________________________________.
Bohr suggested that an electron moves around
the nucleus only in certain allowed
____________________________________

Each orbit was given a number, called the
______________________________________.
o
Bohr orbits are like steps of a __________________, each at a specific distance from the
nucleus and each at a specific energy.

Hydrogen’s single electron is in the ______________ orbit in the
_________________________.
o
When _________________ is added, the electron moves
to the ________________ orbit.

The electron releases _______________________ as it falls back
towards the ground state.

Bohr’s model explained the hydrogen’s spectral lines, but _______________________________
any other element’s lines.

For this and other reasons, the Bohr model was replaced with a more sophisticated model called
the __________________________________________ or wave-mechanical model.
Quantum Mechanical Model:

___________________________________ (1892–1987) hypothesized that particles, including
electrons, could also have _________________________________________________.
o
Electrons do not behave like particles flying through space.


We cannot, in general, describe their exact paths.
_____________________________ showed it is impossible to take any measurement of an
object without ______________________________________.

The _________________________________________________ states that it is fundamentally
impossible to know precisely both the velocity and
position of a particle at the same time.

The only quantity that can be known is the
_________________________ for an electron to
occupy a __________________________ around the
nucleus.

Schrödinger treated electrons as waves in a model called the ____________________________
____________________________________________________.
o
Schrödinger’s equation applied equally well to elements other than ________________
(unlike Bohr’s model).

The quantum mechanical model makes no attempt to __________________________________
_____________________________ around the nucleus.

Instead, Schrödinger’s wave function predicts a three-dimensional
region around the nucleus called the
_______________________________ in which an electron may be
found.

In the quantum-mechanical model, a number and a letter specify an ______________________.
o
The lowest-energy orbital is called the ______________________________.

It is specified by the number _____ and the letter _____.
Hydrogen’s Atomic Orbitals:
 The number is called the _______________________________________________ (n) and it
indicates the relative size and energy of atomic orbitals.
o
n specifies the atom’s major energy levels, called the__________________________
____________________________________.

_______________________________________ are contained within the principal energy levels.

Each energy sublevel relates to orbitals of ________________________________________.

s sublevel:

p sublevel:

d sublevel:

f sublevel:

Orbitals are sometimes represented by ____________, where the dot density is proportional to
the ________________________________ of finding the ________________________.

The ________________________________ for the 1s orbital is greatest near the nucleus and
decreases farther away from the nucleus.

The electron is more likely to be found ________________ to the nucleus than far away from it.

At any given time, hydrogen’s electron can occupy just ________________ orbital.
o
When hydrogen is in the ground state, the electron occupies the __________ orbital.
o
When the atom gains a _____________________ of energy, the electron is excited to
one of the ______________________________ orbitals.