Brief introduction to molecular structure.

1. Brief Introduction to
Chemistry- Part 1
Dr. Mark A. McGinley
Professor, Head of Science Unit
Core Curriculum and General Education Office
Lingnan University

2. Questions to Think About
• What makes up the human body?
• What is found outside of the body?
• What is found inside of the body
• How are bones and hair different?
• What makes bones and hair different?

3. Chemical Structure of Two Proteins
collagen keratin
How are the two structures different?

4. Be careful- capitalizing chemical names
• Decided by the International Union of Pure and Applied Chemists (IUPAC)
http://www.iupac.org/
• The names of chemicals are not capitalized except when they are the first
words in a sentence.
• I like to eat sucrose. Carbon dioxide is a greenhouse gas
• Sucrose may rot my teeth. Plants require carbon dioxide.
• For more information about writing more complex scientific names check
out the following link
• http://expertedge.aje.com/2013/12/03/editing-tip-of-the-week-
capitalization-of-chemical-compounds/

5. Let’s Try Something a Bit Simpler- Two Sugars
glucose fructose

6. Time to Think!!
• How are these two sugars the same?
• How are they different?

7. Think Hierarchically
• World
• Asia
• China
• Hong Kong
• New Territories
• Tuen Mun
• Lingnan University
• Chemistry and Society Class
• You

8. Simple Definitions
• Molecule
• A molecule is the smallest particle in a chemical element or compound that has the
chemical properties of that element or compound. Molecules are made up of atom s
that are held together by chemical bonds.
• Atom
• A unit of matter; the smallest unit of a chemical element.
• Chemical Element
• A chemical element is a substance that contains only one type of atom.
An element is the smallest amount of a substance that can still keep its properties.
• Chemical compound (compound)
• A substance made up of more than one element

9. Hierarchical Thinking Very Important In
Chemistry
• Molecules are made up of atoms
• Compounds are made up of elements
• Which are larger- molecules or atoms?

10. Simple Self Quiz
• Name 3 elements
• Name 3 compounds

11. Back to These Two Sugars
• glucose • fructose
What differences do you notice between
the different atoms?

12. Combine glucose and fructose- sucrose
How is sucrose different from glucose and sucrose?

13. Back to your body
• We can characterize the composition of your body either by mass composition.
For average 70 kg male
mass (kg) % of mass
Oxygen 43.0 65.0
Carbon 16.0 16.0
Hydrogen 7.0 10.0
Nitrogen 1.8 3.0
Calcium 1.0 1.4
Phosphorous 0.8 1.1
> 96 %

14. Your body
• Can also characterize your body by the atomic composition
• A 70 kg male will have 7 x 1027 atoms and at least 60 different elements, about 29 of
which are biologically important
% of atoms
Oxygen 24.0
Carbon 12.0
Hydrogen 62.0
Nitrogen 1.1
Calcium 0.2
Phosphorous 0.2

15. Compare your body’s mass and atomic
composition
% of atoms % of mass
Oxygen 24.0 65.0
Carbon 12.0 16.0
Hydrogen 62.0 10.0
Nitrogen 1.1 3.0
Calcium 0.2 1.4
Phosphorous 0.2 1.1

17. Time to Think Some More
• What do these differences mean?

18. Question
• Are atoms the smallest particles in the universe?
• No
• Atoms are made up of “sub-atomic” particles
• Protons, neutrons, electrons

19. Why do Atoms Have Different Sizes?
• Think about possible reasons that atoms could have different sizes.
• What you are doing is now is coming up with different scientific hypotheses
• Hypothesis- idea about how the world works
• (I can think of at least two alternative hypotheses)

20. Different Elements are Defined by the
Number of Protons They Contain
• 1 proton- Hydrogen
• 2 protons- Helium
• 3 protons- Lithium
• 4 protons- Beryllium
• 5 protons – Boron
• 6 protons- Carbon
• 7 protons- Nitrogen
• 8- protons- Oxygen

21. What is Found in Atoms?
• Protons, neutrons, and electrons
• Protons- relatively heavy, positively charged
• Neutrons- relatively heavy, no charged
• Electrons- very, very light, negatively charge

22. More Info About Atoms
• Protons and neutrons are found in the center of the atom in a region
known as the nucleus.
• Electrons move, “orbiting” around the nucleus.
• Each element contains the same number of protons and electrons
• Because protons have + charge and electrons have – charge, atoms have no
electric charge (neutral)

23. More Info About Atoms
• Elements often contain the same number of neutrons as protons, but
not always
• The same element (defined by # of protons) can have different
numbers of neutrons
• Known as isotopes
• Important when we discuss nuclear energy

24. What holds protons and electrons together?
• What else do you know of that “orbits”?
• What holds those together?

25. Force Holds Orbiting Bodies Together
Gravitational force Force from the string

26. What Holds Electrons and Protons Together?
Very, probably overly simplistic, answer
• Electrons and protons held together by attraction between negative
charge of electrons and positive charge of the proton
• Remember, opposite charges attract
• The more accurate answer to this question is quite interesting, but
much more complex than we need to worry about now. For more
info check out
• What holds the nucleus together?
• http://www.masterorganicchemistry.com/2010/07/16/what-holds-the-
nucleus-together/

27. Visualizing Atoms

28. Orbitals (do not freak out about this now…
we will discuss this as needed in the future)

29. More Realistic Visualization of Hydrogen
Atom
How many protons and electrons in hydrogen atom?

30. More Fun Facts About Atoms
• Mass
• Neutron = 1.6749286*10-27 kg
Proton = 1.6726231*10-27 kg
Electron = 9.1093897*10-31 kg
• Relative Mass
• Neutron = 1
Proton = 0.99862349
Electron = 0.00054386734

31. Review of Sub-atomic Particles

32. Atoms are of different sizes because they contain
different numbers of protons and neutrons.
Hydrogen atom- 1 proton Carbon atom- 6 protons, 6 neutrons

33. Why does this matter?
• The size of atoms and the number of electrons influences their
characteristics and how they react with other atoms.
• This will be a major topic we discuss for the rest of the course.

34. Intended Learning Outcomes
• 1. Be able to define important chemical and scientific terms including
• Molecule, atom, chemical element, chemical compound, proton, neutron, electron,
and
• 2. List the most abundant elements in the human body by weight and by
atomic proportion and discuss the implications of the differences between
the two lists.
• 3. Discuss the differences in the properties of the three sub-atomic
particles.
• 4. Describe what holds the electrons and the protons together in an atom.
• 5. Draw a simple visualization of an atom and correctly identify the correct
parts in the correct locations.