Wednesday, April 30, 2008

All About Atoms!

This week we have kicked off our study of atoms. Here is the handout you received.
All About Atoms!

Think of some of the smallest objects you know. You may think of grains of sand, a speck of dust, or a cell in the human body. Matter is made up of even smaller units. Scientists call the tiny units atoms. An atom is the smallest piece of an element that has the properties of that element. Atoms are the building blocks of all matter. You cannot see atoms by just looking for them. Atoms are too small to see. Scientists use a special microscope called an electron scanning microscope to produce images of some atoms. Scientists carefully observe the way matter acts, and by doing so, they have formed models of atoms. This model is still changing as scientists gain more knowledge about the behavior of these tiny particles.

The latest model shows that all atoms have a central core called the nucleus, which contains protons and neutrons. A proton is a particle in an atom that has a positive electrical charge. A neutron is a particle in an atom with no electrical charge. Protons and neutrons have similar masses. Together they make up most of the mass of an atom.

The nucleus is surrounded by a cloud of particles called electrons. Electrons are a particle with a negative electric charge. The electrons are always moving around the nucleus of an atom. Scientists say that the electrons form a “cloud” around the nucleus. We cannot be sure just where the electrons are found in the cloud. We know that electrons can “jump” from one level to another in certain atoms and that certain atoms can gain or lose electrons more easily than others. The model may change as we learn more about atoms.

Although the mass of a proton is much greater than that of an electron, the amount of electrical charge each has is the same. In an atom, the number of positively charged protons equals the number of negatively charged electrons. Therefore the charge of the atom is zero.

Several other important facts about atoms are:

1. All atoms of the same element have the same mass. Atoms of different elements have different masses.

2. Atoms make up molecules.

3. Information about atoms may be found in the Periodic Table of the Elements.

4. The atomic number is the number of protons in each atom.

5. The number of neutrons in an atom may be determined by subtracting the number of protons from the atomic mass of the atom.

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