Transcript Discovering Parts of the Atom

Understanding the Atom
4-2: Discovering Parts of the
Atom
4-2 Vocabulary
spectral line
energy level
electron cloud
History of the Atom
Many scientists, Thomson and
Rutherford to name a few, performed
experiments that led to a better
understanding of the atom and its
subatomic particles.
Bohr and the Hydrogen Atom
A Danish scientist, Niels Bohr,
studied the hydrogen atom and then
proposed a new model for the
arrangement of electrons in an atom.
Bohr and the Hydrogen Atom
(cont’d)
A spectral line is a
single wavelength of
light that can be seen
when the light from an
excited element is
passed through a
prism.
When excited,
hydrogen and neon
give off unique narrow
bands of light on the
spectrum.
Bohr and the Hydrogen Atom
(cont’d)
An energy level is a
region in space
corresponding to a
certain energy
through which an
electron moves.
Bohr and the Hydrogen Atom
(cont’d)
Bohr proposed that
electrons move in
circles around the
nucleus.
The electrons can
move only in an orbit
that is a set distance
from the nucleus.
Each energy level can
hold a certain number
of electrons.
Bohr and the Hydrogen Atom
(cont’d)
Electrons fill the energy levels in order.
The lowest level is filled first (that closest to
the nucleus).
The second level has no electrons until the first
level is full.
The first level holds 2 electrons, the second
level holds 8 electrons.
The last energy level may or may not
be filled.
Bohr and the Hydrogen Atom
(cont’d)
An element will react with other
elements to try to receive a full outer
energy level. (also known as “completing the
octet”)
For example, if an atom has 6 electrons in its
outer energy level, it may bond with another
atom that contains 2 electrons in its outer
energy level OR two of the same atom that
contains 1 electron in its outer energy level.
Bohr’s Atomic Models
This diagram shows how electrons are
placed in the elements with atomic
numbers 1–10 (according to Bohr’s model).
Bohr’s Atomic Models
(cont’d)
Different numbers of electrons in outer energy
level results in different elements.
Unreactive elements have a full outer energy level.
Elements with incomplete outer energy levels are
likely to form compounds.
The Electron Cloud
Today scientists think of an electron in an
atom as being in an electron cloud, which is
a region surrounding an atomic nucleus
where an electron is most likely to be
found.
Electron
Cloud
Model
4-2 Lesson Review Questions
Atoms of the same element always have the
same number of ____.
A electrons
B neutrons
C protons
D photons
4-2 Lesson Review Questions
Elements that do not react with other
elements must have ____.
A completely filled
energy levels
B excited electrons
C empty energy levels
D the same number of
protons and neutrons
4-2 Lesson Review Questions
What is the maximum number of electrons
the lower energy level (closest to the
nucleus) can hold ?
A1
B2
C6
D8
Homework
Answer the three multiple choice lesson
review questions
Write a “Step-Up-To-Writing” style
paragraph the answer the following
question: “Have you ever noticed, or
needed to find evidence for, something
that was not directly observable?
Besides learning about the structure of
atoms, can you think of other ways
people try to collect clues about things
they cannot see directly?”