THE ELECTRON THEORY

The word electricity comes from the Greek word electron, which means amber. The whole effects of electricity take place because of the existence of the electron. While no one has actually seen an electron, but only the effects it produces, we call the laws governing its behavior the electron theory. Electron theory is not only the foundation for the design for all the electrical and electronic equipment. It also gives details on physical and chemical action and helps scientist to investigate into the very nature of the universe and the existence itself.
MATTER, ELEMENTS, AND COMPOUNDS

Matter is whatever thing occupies space and has weight and mass. There are four states of matter: solid, liquid, gas or plasma. Examples of matter are the clothing we wear, the water we drink and the air we breathe. Matter may either be an element or a compound.

Element is the basic building block of nature. It is substance that cannot be reduced to simpler one by chemical means. There are more 100 known elements today. Examples of elements are gold, platinum, oxygen, hydrogen, etc.

Compound is a chemical combination of two or more elements. It can be divided by chemical means but not by physical means. Examples of compounds are table salt (NaCl), which composes of sodium and chlorine, and water (H­₂O), which composes of hydrogen and oxygen. Molecule is the smallest part of a compound that maintains the chemical properties of such compound. Molecule is the chemical combination of two or more atoms. Atom is the smallest particle of an element that retains the characteristic of the element.

Physical combination of elements and compounds is called mixture. Examples of mixtures include air, which made up of oxygen, nitrogen, carbon dioxide, and other gases, and salt water, which consists of water and salt.


THE STRUCTURE OF THE ATOM

Hydrogen is the simplest and smallest atom. You see that the hydrogen atom is like a sun with one planet revolving around it. The planet is known as an electron and the sun is known as the nucleus.

Each atom has a nucleus. The nucleus is situated at the center of the atom. It has positively charged particles called protons and uncharged particles called neutrons.The negatively charged particles called electrons orbit around the nucleus.

An atom has the same number of protons and electrons, and said to be electrically neutral. A neutral atom that gains one or more electrons is no longer neutral. It is said to be negatively charged and is called as negative ion. A neutral atom that losses one or more electrons is said to be positively charged and is called as positive ion.

SELF -TEST(REVIEW QUESTIONS)

1. What is the basic point of the electron theory?
2. What is a molecule? An element?
3. Is the nucleus of an atom positively or negatively charged?
4. What is the charge of an electron?
5. What are electrons?

SELF-CHECKING EXERCISES

Column A ________1. molecule ________2. atom ________3. electron ________4. nucleus ________5. element ________6. compound ________7. matter ________8. proton ________9. neutron ________10. positive ion

Column B a. Atoms that losses electrons b. Smallest part into which an element can be divided retaining the properties of such an element. c. It does not carry any charge at all. d. Smallest particle of a compound that still retains the property of such compound. e. Positively charged particle of an element. f. Negatively charged particle of an element. g. Anything that occupies space and has weight. h. Dense central portion of atom. i. Chemical combination of two or more elements