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Atoms and elements

Atoms and Elements


The next unit investigates the building blocks of matter and corresponds to pages 119-157 in the text. Obviously there can be tremendous depth at the atomic level. We will strive to understand the basic building blocks of atoms (protons, neutrons, and electrons) and how they affect the atom's properties like reactivity, radioactivity, conductivity, etc.


Atoms and elements

So what are the tiny particles that all matter is made of?


People have wondered that for many, many years. In ancient greece (400 BC) Democritus gave the tiny, unseen substances the name atom. Over the years atom has been defined as the building blocks of all matter. Only in 2005 has anyone even claimed to have seen one, yet we know all sorts of stuff about them. We learned about atoms the way you learned what was in you “black box” and may very well be wrong.


Ernest Rutherford (1911--England) probed the atoms’ structure and guessed that atoms are made of Protons, Electrons and Neutrons (each of these are made of even smaller, sub-atomic particles like muons, quarks, mesons, and neutrinos).

Protons have significant mass and a positive charge.

Electrons have an insignificant mass and a negative charge.

Neutrons have mass and no charge.

The protons and neutrons are found in the center of the atom. It gets the name, "nucleus" (note that almost all the mass is there).

Meanwhile electrons zip around the nucleus in wild orbits like satellites around a planet.

Draw this:


The electrons stay around the nucleus for the most part due to electrical attractions to the protons. But protons want to repel from one another. The neutrons are there to keep the peace.


1800’s John Dalton (English) developed the “atomic theory” which we have refined into:

1 all matter is made of very small particles called atoms

2 all atoms of the same element are the same, and different from other


3 all atoms have an average mass characteristic of the element

4 atoms of different elements have different average masses

5 atoms cannot be broken into smaller particles during ordinary



How many different building blocks (atoms) are there?

In ancient greece--four (earth, air, fire, water)--the elements!

During the middle ages alchemists tried to answer this by breaking things apart into the most simplified substances they could and started keeping careful lists. They got 20 or so and kept the name element. Today we have discovered (or created) 120 or so and define an element as any substance that cannot be separated into different substances by chemical means. They have been organized by properties into the periodic table of elements.

Here is a guide to reading the table (metals, noble gasses, etc.)

Here is how to read the table:


#protons           weight



Sometimes an element will have too many or too few electrons or neutrons. Here is what they are called:





elements in the same group have similar properties

Metal (conductors of heat and electricity, shiny, malleable) vs non-metal vs metalloids

Alkali metal family (I): VERY reactive

Alkali metal family (II): reactive

Halogen family: react with alkali to form white solid salts

Noble gas family: Non-reactive!!!


Draw and label an atom of based on the info on the table of elements.

Which elements are more reactive?

Which ones are really stable?

Which are the lightest?

What is an ion?

What is an isotope?


If you have enjoyed the topics in this unit, feel free to investigate further. Here are some ideas. These are NOT required, but I hope you have fun and delve into some of them:


Construct a 3D model of an atom out of original material (be creative).


Research any of the scientists who contributed to our atomic understanding.


What is a quark? A muon? A nutrino? Find out and teach the rest of us about these sub-atomic particles.


Reorganize the periodic table of elements by your own system and tell me why yours is better.


Memorize the elements song or make your own up.


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