A Boy And His Atom:
The World's Smallest Movie
You're about to see the movie that holds the Guinness World Records™ record for the World's Smallest Stop-Motion Film. The ability to move single atoms — the smallest particles of any element in the universe — is crucial to IBM's research in the field of atomic memory. But even nanophysicists need to have a little fun. In that spirit, IBM researchers used a scanning tunneling microscope to move thousands of carbon monoxide molecules (two atoms stacked on top of each other), all in pursuit of making a movie so small it can be seen only when you magnify it 100 million times. A movie made with atoms.
1. Development of the Atomic Theory
The 2,400-year search for the atom
How do we know what matter is made of? The quest for the atom has been a long one, beginning 2,400 years ago with the work of a Greek philosopher and later continued by a Quaker and a few Nobel Prize-winning scientists. Theresa Doud details the history of atomic theory.
This reminds us of the tentative nature of science. Scientific knowledge can be subjected to revision or improvement if we obtain new evidence or if there a reinterpretation of existing evidence. Even though science is not absolute, it is still robust as it has gone through many debates and validation.
Bohr’s “planetary model” states that electrons are in specific energy levels or “orbits” around the nucleus. Explain how this is not possible using Heisenberg’s uncertainty principle.
Explain what might have been Thomson’s thought process when he discovered the electron and used his discovery to come up with his ‘chocolate chip cookie’ model of the atom.
Compare and contrast Dalton’s model, Thomson’s model, Rutherford’s model, and Bohr’s model of the atom.
What role do you think popular belief has on scientific discoveries? Is there something in today’s world that has been overshadowed by popular belief? Explain.
2. The Structure of an Atom
Meet the subatomic particles
Scale of the Universe
INSTRUCTIONS
How does the size of an atom compare to other objects? Use the following simulation to find out!
Build an Atom
INSTRUCTIONS
Build different atoms with this applet. What kind of atoms are stable/unstable?
What force holds the protons, electrons and neutrons in an atom?
Wouldn’t the repulsive forces between protons and protons, and between electrons and electrons destabilize an atom?
If opposite charges attract, why don’t electrons collide with the nucleus?
Have you ever wondered...
3. The Proton Number and Nucleon Number
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Each element has a unique proton number. Atoms of different elements have different proton numbers.
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Since all atoms of elements are electrically neutral, no. of electrons = no. of protons.
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If the particle is an ion (meaning that it has gained or lost electrons), the charge is written as a superscript (+, 2+, 3+… or –, 2–, 3– …).
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No. of neutrons = mass number – atomic number.
4. Isotopes
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Isotopes are atoms of the same element that have the same number of protons but different number of neutrons.
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Isotopes have the same chemical properties (as they have the same number of valence electrons) but different physical properties (as they have different masses).
Can you drink heavy water?
Heavy water (or deuterium oxide) is a form of water that contains a larger than normal amount of the hydrogen isotope deuterium, rather than the common hydrogen-1 isotope that makes up most of the hydrogen in normal water. Here's more about heavy water including a discussion of its role in World War II and whether it is dangerous to humans.
Carbon Dating
Carbon dating is a technique for determining the age of things made from plant or animal material. It was developed by a team of chemists in the United States, led by Willard Libby. The tissues of all living things contain the element carbon. Carbon has three isotopes (carbon-12, carbon-13 and carbon-14). The proportion of these isotopes in living things is contant.
However, once an organism dies, the proportion changes. This is because atoms of carbon-14, which is an unstable isotope, slowly decay and are not replaced as they are in living things. Therefore, the amount of carbon-14 gradually decreases. By finding out how much carbon-14 there is in an object, scientists can determine how long ago a piece of once-living material is.
Note: Isotopes that decay are said to be radioactive. Most isotopes are non-radioactive.
5. Electronic Structure of an Atom
6. Forming Ions
What are ions?
An ion is a charged particle formed when an atom loses or gains electrons.
When atoms gain or lose electrons to form ions , it often results in them attaining the duplet or octet electronic configuration of a noble gas.