There are three main types of chemical bonds: ionic bonds, covalent bonds, and hydrogen bonds. Ionic bonds involve the transfer of electrons between atoms, covalent bonds involve the sharing of electrons between atoms, and hydrogen bonds are weak attractions between polar molecules containing hydrogen, such as water molecules. Chemical bonds are crucial as they hold atoms and molecules together, allowing for the formation of larger biological compounds like proteins.

1. CHEMICAL BONDS
Companion Text:
Herlihy, B, The Human Body in Health and Illness, 4th Edition, 2011,
Saunders Elsevier
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2. Atoms are attracted to each other because
they want to achieve a stable outer
electron shell …
In other words, they want either to fill or
empty the outer electron shell
Herlihy, B, 2011, p.17
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3. The force of attraction that occurs between
the atoms is like the force of two magnets
When you try to separate the magnets you
can still feel the pull
(Herlihy 2011)
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4. 4
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5. The electrical attraction between
atoms is called a chemical bond
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6. There are three (3) kinds of chemical
bond
• Ionic Bonds
• Covalent Bonds
• Hydrogen Bonds
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7. IONIC BONDS
An ionic bond happens when electrons
are transferred between atoms
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8. Rather like moving house!
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9. 9
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10. COVALENT BOND
In a covalent bond, the outer shells of
the atoms share electrons
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11. Covalent bonding is like holding hands
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13. Water happens because of covalent
bonding …
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14. Covalent Bond
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15. Covalent bonds are strong and do not
break apart in water …
Proteins and Carbohydrates are formed by
covalent bonding.
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16. The strength of these bonds is important
because the protein produced by the body
must not fall apart when exposed to water
Herlihy, B, p.17 (2011)
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17. Many proteins, such as hormones, are
transported around the body in blood, and
blood is made up mainly of water’
If the covalent bonds of the protein broke
apart in water the hormones would not be
able to accomplish their tasks
Herlihy, 2011, p.17
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18. Many chemical reactions that happen in
the body involve carbon.
Because of this a separate branch of
chemistry called organic-chemistry studies
only carbon-containing substances
Inorganic chemistry studies non-carboncontaining substances
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19. HYDROGEN BONDS
This kind of bond is different to ionic and
covalent bonds
A hydrogen bond is not caused by either
the transfer or the sharing of electrons in
the outer shells of the atom
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20. Hydrogen Bonds are best described
as the weak attraction between water
molecules
Herlihy, B, P.18 (2011)
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21. Water is composed of hydrogen and
oxygen
The weak positive charge around the
hydrogen of one water molecule is
attracted to the weak negative charge of
the oxygen in a second water molecule
Herlihy, 2011, p.18
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22. POLARITY
Water engages in hydrogen bonding because it
is a polar molecule
A polar molecule has a ‘lop-sided’ charge (a +
end and a – end)
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23. 0
Neg
2
Pos
H+
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25. Hydrogen Bond
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26. Several other terms are related to the
activity of electrons in the outer shells of
the atoms …
Herlihy, 2011, p.19
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27. Electrons, for instance carry a (-ve)
charge, and if they are lost from or gained
by the outer shell of an atom, the electrical
charge of the atom changes
Herlihy, 2011, p.19
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28. The electrical charge of the atom or
element changes from a neutral charge
(no charge) to either a positive (+) or a
negative (-) charge
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29. Atoms that carry an electrical charge are
called ions
If an ion is positively charged it is called a
cation
If an ion is negatively charged it is called
an anion
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30. An electrolyte is a substance that forms
ions when it is dissolved in water
Electrolytes can conduct an electrical
current
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31. For Example …
The electrocardiogram (ECG) records
the electrical events of the heart.
It is the movement of ions through
the tissues that cause the electrical
events to be recorded on the ECG
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33. So how are ions formed?
Ions are formed when the outer shell of
the atom loses or gains electrons
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34. For instance …
The sodium atom has 11 protons (+ve)
and 11 electrons (-ve) …
If a single electron is donated the sodium is left
with 11 positive (+) charges and only 10
negative (-) charges
The sodium is said to carry a net charge of +1
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35. The sodium ion is therefore a cation and is
represented as Na+
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36. and …
The chlorine atom has 17 protons (+) and
17 electrons (-ve)
If an electron is gained, the chlorine then
contains 17 (+) charges and 18 (-) charges
The chlorine has a net charge of -1, so it is
an anion
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37. Some atoms give up more than one (-ve)
electron so they have a more positive charge
Calcium is an example, because it gives up 2
electrons – its chemical symbol is therefore
Ca2+
Herlihy, 2011, p.19
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38. Ionization
Ionization happens when an electrolyte
splits or breaks apart in solution
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39. For Example …
NaCl (sodium chloride) is an electrolyte.
In its solid state it looks like tiny white
granules
When it is dissolved in water the table salt
dissociates
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40. The ionic bonds holding the sodium and
chloride together weaken and the solid
NaCl splits into Na+ (sodium ion) and Cl(chloride ion).
The NaCl has dissociated and because
the products are ions, the process is called
ionization
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41. Remember!
Only electrolytes ionize
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42. What is a Molecule?
A molecule is formed when two or more atoms
bond together …
Two identical atoms can bond, for instance –
one atom of oxygen can bond with another atom
of oxygen to form a molecule of oxygen which is
called 02
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43. A molecule can also be formed when
atoms of different elements combine.
For example – when 2 atoms of hydrogen
combine with 1 atom of oxygen a
molecule of water is formed
Herlihy, 2011, p.20
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44. COMPOUNDS
A substance that contains molecules formed by
two or more different atoms is called a
compound …
We can use the example of water again – when
2 atoms of hydrogen and 1 atom of oxygen
combine
Water is considered to be both a molecule and a
compound
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45. Some Important Compounds &
Molecules
• Water
• Oxygen
• Carbon Dioxide
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46. Water …
• Most abundant compound in the body
• Makes up nearly 2/3 of an adult’s body weight
• Essential to life
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47. UNIVERSAL SOLVENT
Water is the universal solvent because
most substances dissolve in water
When substances are dissolved in water
they move more easily and this facilitates
their involvement in chemical reactions
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48. REGULATES TEMPERATURE
Water can absorb large amounts of heat without
dramatically increasing the temperature of the
water itself
This means that heat can be removed from heatproducing tissue, like exercising muscle, while
the body maintains a normal body temperature
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49. WATER AS A LUBRICANT
Water is a major component of mucus and other
lubricating fluids
These lubricating fluids decrease friction when
two lubricating surfaces slide past each other
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50. WATER IN CHEMICAL REACTIONS
Water often has a crucial role to play in chemical
reactions
We need water to break down carbohydrates
during digestion
Herlihy, 2011, p.20
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51. WATER AS A PROTECTIVE DEVICE
Water also protects important structures.
The cerebrospinal fluid that surrounds and cushions the
brain and spinal cord is an example
Amniotic fluid surrounds and cushions the developing
infant in its mother’s womb
Herlihy, 2011, p.20
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52. OXYGEN
Oxygen (02) exists in nature as a gas and is essential to
life
There is 21% of Oxygen in the air that we breath
Oxygen is used by the cells to liberate energy from the
food we eat. This energy powers the body
If there is no energy, the body like a motor without fuel
stops running and we die.
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53. CARBON DIOXIDE
Carbon Dioxide (CO2) is a compound that
consists of one carbon atom and two oxygen
atoms …
CO2 is a waste product and must be eliminated
from the body.
It is made when food is chemically broken down
for energy
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54. CHEMICAL REACTIONS
A chemical reaction is a process whereby the
atoms of molecules or compounds interact and
form new chemical combinations
For example, glucose interacts with oxygen to
form carbon dioxide, water and energy
Herlihy, 2011, p.21
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55. CHEMICAL REACTIONS … Cont.
The rate of chemical reactions are important
Most of them take place quite slowly , and
chemical substances called catalysts can
speed them up
Enzymes are proteins that are acting as
catalysts
Most chemical reactions need a catalyst or an
enzyme
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56. REFERENCE
Herlihy, B, The Human Body in Health and Illness, 4th
Edition, 2011, Saunders Elsevier
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