Brief Introduction to Chemistry- Part 1

Dr. Mark A. McGinleyProfessor, Head of Science Unit

Core Curriculum and General Education OfficeLingnan University

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?

Chemical Structure of Two Proteins

collagen keratin

How are the two structures different?

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-chem

ical-compounds/

Let’s Try Something a Bit Simpler- Two Sugarsglucose fructose

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

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

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

Hierarchical Thinking Very Important In Chemistry• Molecules are made up of atoms

• Compounds are made up of elements

• Which are larger- molecules or atoms?

Simple Self Quiz• Name 3 elements

• Name 3 compounds

Back to These Two Sugars• glucose • fructose

What differences do you notice between the different atoms?

Combine glucose and fructose- sucrose

How is sucrose different from glucose and sucrose?

Back to your body• We can characterize the composition of your body either by mass composition. For

average 70 kg male

mass (kg) % of massOxygen 43.0 65.0Carbon 16.0 16.0Hydrogen 7.0 10.0Nitrogen 1.8 3.0Calcium 1.0 1.4Phosphorous 0.8 1.1 > 96 %

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 12.0Hydrogen 62.0Nitrogen 1.1Calcium 0.2 Phosphorous 0.2

Compare your body’s mass and atomic composition

% of atoms % of massOxygen 24.0 65.0Carbon 12.0 16.0Hydrogen 62.0 10.0Nitrogen 1.1 3.0Calcium 0.2 1.4Phosphorous 0.2 1.1

https://en.wikipedia.org/wiki/File:Two_pie_graphs_about_the_composition_of_the_human_body.png

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

Question

• Are atoms the smallest particles in the universe?• No• Atoms are made up of “sub-atomic” particles

• Protons, neutrons, electrons

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)

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

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

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)

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

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

Force Holds Orbiting Bodies TogetherGravitational force Force from the string

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-nucleu

s-together/

Visualizing Atoms

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

More Realistic Visualization of Hydrogen Atom

How many protons and electrons in hydrogen atom?

More Fun Facts About Atoms• Mass• Neutron = 1.6749286*10-27 kg

Proton = 1.6726231*10-27 kgElectron = 9.1093897*10-31 kg

• Relative Mass• Neutron = 1

Proton = 0.99862349Electron = 0.00054386734

Review of Sub-atomic Particles

Atoms are of different sizes because they contain different numbers of protons and neutrons.

Hydrogen atom- 1 proton Carbon atom- 6 protons, 6 neutrons

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.

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.