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CHEMISTRY FORM 2


1. STRUCTURE OF THE ATOM, AND THE PERIODIC TABLE
2. CHEMICAL FAMILIES AND PATTERNS IN PROPERTIES
3. CHEMICAL BONDING AND STRUCTURE
4. SALTS
5. EFFECT OF AN ELECTRIC CURRENT ON SUBSTANCES
6. CARBON AND SOME OF ITS COMPOUNDS
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Structure of the Atom, and the Periodic Table: Structure of the atom

1.0 Structure of the Atom, and the Periodic Table


1.1 Structure of the atom


Atom

Previously, we defined an atom as the smallest particle (of an element) that can take part in a chemical reaction. Although it is the smallest, an atom also has parts, called sub-atomic particles, just like a cell in living things also has parts.


What is a structure?

Parts of an object and the way they are arranged in the object make up a structure. Examples of a structure are classroom with floor, walls, desks, and roof as its parts; a bicycle wheel with the rim, spokes and hub as parts; merry-go-round, and the solar system (the image below).



high school chemistry,Form 2, Atomic strucure image

Structure of the atom

An atom consists of protons, neutrons and electrons as sub-atomic particles. Protons and neutrons occupy the centre, called the nucleus, while electrons are some distance away from the nucleus.


Protons are positively (+) charged, neutrons are neutral (0 electrical charge) and electrons are negatively (-) charged. Protons and neutrons are called nucleons, because they are in the nucleus.


Table 1.1.1: Charges on sub-atomic particles high school chemistry, charges on sub atomic particles

Is the symbol,, familiar? This is a basic symbol of science. It represents movement of electrons around the nucleus, similar to the movement of planets around the Sun, or rim around the hub. But it is a three-dimensional drawing which is rather complex. We will use simplified two-dimensional drawings (Figure 1.1.1).


high school chemistry,Form 2, Atomic strucure image

Figure 1.1.1: Atomic structure


A proton may be represented by p, or +; neutron by n or o, and electron by e, -, dot, or cross (x).


Questions 1.1

  1. Name three (3) particles found in an atom.
  2. What are nucleons?
  3. Describe the arrangement of sub-atomic particles in an atom.

Answers to Questions 1.1