Atomic Structure Definition Key Points

3.4 Atomic Structure Definition Key Points

1.       Matter is anything that occupies space and has mass.

2.       The smallest particle of matter that can take part in a chemical reaction is called an atom.

3.       An atom consists of protons, neutrons and electrons.

4.       The protons and neutrons form the nucleus of the atom.

5.       Protons and neutrons are collectively known as nucleons.

6.       The atomic number of an element indicates the number of protons in the nucleus of its atom.

7.       The number of electrons in the outermost orbit is the valence electrons.

8.       Electrons carry a negative charge; while protons carry a positive charge. Charged atoms or molecule are called ions.

9.       Most metals contain free electrons which, at room temperatures, roam the spaces between the atoms.

10.    In most substances, atoms team up to form molecules.

11.    Electrons moving in a given direction give rise to an electric current. An electric circuit is a closed path through which an electric current may flow.

12.    Electrically, materials can be grouped as:

a.        conductors,

b.       semi-conductors, and

c.        insulators.

13.    Conductors are those materials which have free electrons. The most common conductors are made of copper and aluminium.

14.    Semi-conductors have few free electrons at low temperatures, but have many free electrons at higher temperatures.

15.    The most commonly used semi-conductors are silicon and germanium. They are used for making diodes, transistors and integrated circuits.

16.    Insulators have no free electrons and do not conduct an electric current.