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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: Noble gases (Group VIII elements)

1.0 Structure of the Atom, and the Periodic Table


2.4 Noble gases (Group VIII elements)


Noble gases include helium (He), neon (Ne), argon (Ar), xenon (Xe), and krypton (Kr). Being in Group VIII, their outermost (and inner) energy levels are completely filled with electrons so they are chemically stable (Figure 2.4.1).


high school chemistry, Noble gas atomic structures

Figure 2.4.1: Noble gas atomic structures


Atomic radii of nobe gases increase down the group due to an increase in number of energy levels.


Table 2.4 Atomic radii and melting points of noble gases

Element Atomic radius (nm) Melting point (oC)
Helium 0.128 -270
Neon 0.160 -249
Argon 0.192 -189


Questions 2.4

  1. Noble gases exist as single atoms (mono-atomic molecules). Explain this.
  2. Although stable and unreactive, some noble gases can be made to react under extreme conditions, such as high temperatures. Which of the elements would be the most difficult to be made to react? Explain your answer.

Answers to Questions 2.4


Noble gases are used in many areas such as in diving and mountaineering gas cylinders, welding, light emitting diodes (LED) and advertisement sign lamps (Figure 2.4.2) because of their rich colored lights.


Figure 2.4.2 Uses of noble gases (courtesy AudioAfricionado.org)


Summary about noble gases

  1. Noble gases include helium (He), neon (Ne), argon (Ar), krypton (Kr), and xenon (Xe)
  2. They are all gases.
  3. Their atomic radii increase down the group because of increasing number of energy levels.
  4. They are unreactive.