Download Lecture 4.03 - Bohr`s Atomic Model

Bohr’s Atomic Model
Bohr’s Atomic Model
• In 1913, Neils Bohr, a Dane, proposed his model of the
atom. It was a modification of the Rutherford model.
Bohr however put the electrons in certain circular orbits
called shells or principal energy levels (PEL’s).
1st shell (2
electrons max.)
Nucleus
Empty
space
+
2nd shell (8
electrons max.)
3rd shell (18
electrons max.)
The “planetary” model
Bohr’s Atomic Model
• Protons and neutrons are found in the nucleus.
• Electrons orbit the nucleus in various shells.
• Everything else is empty space.
1st shell (2
electrons max.)
Nucleus
Empty
space
+
2nd shell (8
electrons max.)
3rd shell (18
electrons max.)
The “planetary” model
Bohr’s Atomic Model
Q:What are the Bohr models for the neutral atoms of the
three isotopes of hydrogen?
A: Step-1 Draw a box to represent the nucleus.
Step-2 Determine the number of protons and neutrons
and place them in the nucleus.
Step-3 Draw one circle around the nucleus to represent
the electron shell and then place the one electron in the
shell.
1p
0n
H-1
e-
1p
1n
H-2
e-
1p
2n
H-3
e-
Bohr’s Atomic Model
Q:What are the Bohr models for the neutral atoms of the
two isotopes of carbon?
A: Step-1 Draw a box to represent the nucleus.
Step-2 Determine the number of protons and neutrons
and place them in the nucleus.
Step-3 Draw two circles around the nucleus to represent
the electron shells and then place the six electron in the
shells as indicated by the electron configuration.
ee-
e6p
6n
e-
e-
e-
C-12
ee-
e6p
8n
e-
ee-
C-14
Bohr’s Atomic Model
Q:What are the Bohr models for the neutral atom 27Al and
the ion 23Na1+ ?
A: Step-1 Draw a box to represent the nucleus.
Step-2 Determine the number of protons and neutrons
and place them in the nucleus.
Step-3 As indicated by the electron configuration, draw
arcs to represent the electron shells and place the
electron on them.
13p
14n
27Al
2e-
8e-
3e-
11p
12n
23Na1+
2e-
8e-
0e-
Bohr’s Atomic Model
Q:What are the Bohr models for the ion 37Cl1- and the
neutral atom of calcium-42?
A: Step-1 Draw a box to represent the nucleus.
Step-2 Determine the number of protons and neutrons
and place them in the nucleus.
Step-3 As indicated by the electron configuration, draw
arcs to represent the electron shells and place the
electron on them.
17p
20n
37Cl1-
2e-
8e-
8e-
20p
22n
2e-
8e-
Calcium-42
8e-
2e-
Bohr’s Atomic Model
• The last shell holding electrons is called the valence.
• Electrons in the last shell are called valence electrons.
Q: How many valence electron are there in 37Cl1-?
A: 8
Q: Which shell in a neutral atom of calcium-42 is the
valence?
A: 4th
17p
20n
37Cl1-
2e-
8e-
8e-
20p
22n
2e-
8e-
Calcium-42
8e-
2e-