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Aug 29, 2012
The Chemical Context of Life: Atoms, Bonding, Molecules
Today’s Topics: • Atomic Structure and
bonding – Periodic Table
• Ionic Bonds • Covalent Bonds
Sodium Chlorine Sodium Chloride
+
Figure 2.2
Structure of Atoms
Helium
Electrons are arranged in SHELLS
• The periodic table of the elements shows the electron distribution for all the elements
Second shell
Helium 2He
First shell
Third shell
Hydrogen 1H
2 He
4.00 Atomic mass Atomic number Element symbol
Electron-shell diagram
Lithium 3Li
Beryllium 4Be Boron
3B Carbon
6C Nitrogen 7N
Oxygen 8O Fluorine
9F Neon 10Ne
Sodium 11Na
Magnesium 12Mg
Aluminum 13Al Silicon
14Si Phosphorus
15P Sulfur
16S Chlorine
17Cl Argon
18Ar
Figure 2.8
2
Isotopes differ in the number of neutrons
Are these isotopes charged?
Do they have different chemical bonding properties?
12C 99% 13C 1% 14C tiny bit
Second shell
Helium 2He
First shell
Third shell
Hydrogen 1H
2 He
4.00 Atomic mass Atomic number Element symbol
Electron-shell diagram
Lithium 3Li
Beryllium 4Be Boron
3B Carbon
6C Nitrogen 7N
Oxygen 8O Fluorine
9F Neon 10Ne
Sodium 11Na
Magnesium 12Mg
Aluminum 13Al Silicon
14Si Phosphorus
15P Sulfur
16S Chlorine
17Cl Argon
18Ar
Fig 2.8
Figure 2.13
Ionic Bonding
Na Sodium Atom
Cl Chlorine Atom
Na+
Sodium Ion Cl- Chloride Ion
Sodium Chloride (NaCl)
Neutral Charged “ions”
Second shell
Helium 2He
First shell
Third shell
Hydrogen 1H
2 He
4.00 Atomic mass Atomic number Element symbol
Electron-shell diagram
Lithium 3Li
Beryllium 4Be Boron
3B Carbon
6C Nitrogen 7N
Oxygen 8O Fluorine
9F Neon 10Ne
Sodium 11Na
Magnesium 12Mg
Aluminum 13Al Silicon
14Si Phosphorus
15P Sulfur
16S Chlorine
17Cl Argon
18Ar
Figure 2.8
Second shell
Helium 2He
First shell
Third shell
Hydrogen 1H
2 He
4.00 Atomic mass Atomic number Element symbol
Electron-shell diagram
Lithium 3Li
Beryllium 4Be Boron
3B Carbon
6C Nitrogen 7N
Oxygen 8O Fluorine
9F Neon 10Ne
Sodium 11Na
Magnesium 12Mg
Aluminum 13Al Silicon
14Si Phosphorus
15P Sulfur
16S Chlorine
17Cl Argon
18Ar
Figure 2.8
3
Covalent Bond Formation Hydrogen Atoms
Hydrogen Molecule
Name (molecular formula)
Electron-shell diagram
Structural formula
Space- filling model
Methane (CH4).
Water (H2O). H O
H
H H
H
H
C
Figure 2.11
Space-filling model
Hybrid-orbital model (with ball-and-stick
model superimposed) Unbonded Electron pair
104.5°
O
H Water (H2O)
Methane (CH4)
H
H H
H
C
O
H
H
H
C
Ball-and-stick model
H H
H
H
Figure 2.16
Fig. 2-12b
Oxygen (O2)
Name and Molecular Formula
Electron- distribution
Diagram
Lewis Dot Structure and
Structural Formula
Space- filling Model
Double Bonds
These oxygen atoms share two pairs of electrons.
4
Molecular Shape determines Function
Fig. 2-18
Natural endorphin
Endorphin receptors
Morphine
Morphine
Natural endorphin
Key Carbon Hydrogen
Nitrogen Sulfur Oxygen
Molecular Shape
Determines Function
Non-polar Polar
Partial negative charge on the oxygen;
Partial positive on the hydrogen.
Oxygen is more electronegative than hydrogen
Water
polar covalent bond
