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?
4. Be careful- capitalizing chemical names
• Decided by the International Union of Pure and Applied Chemists (IUPAC)
• 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
8. Simple Definitions
• 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.
• 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
• Molecules are made up of atoms
• Compounds are made up of elements
• Which are larger- molecules or atoms?
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
15. Compare your body’s mass and atomic
% 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
• Are atoms the smallest particles in the universe?
• 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
• 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?
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?
30. More Fun Facts About Atoms
• 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
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,
• 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
• 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.