BAKER HUGHES - Drilling Fluids Reference Manual

Water Based Drilling Fluids
Figure 3-3
The Formation of Water and carbon Dioxide as Examples of Covalent Bonding
Atoms can share one, two, or three electrons, thus forming single, double, or triple bonds. These
bonds are denoted by lines joining the two atoms together. For example, carbon can form each of
the following compounds all of which contain a single, double, and triple carbon-carbon bond,
respectively. Although these compounds are made up of the same two elements, they differ in
their chemistry due to the different carbon-carbon bonds present.
H
H
H
C – C
H
Ethane
H
H
H
C = C
H
H
H
Ethylene (Ethene)
Valency
Figure 3-4
Differences in Compounds due to Chemistry
The numbers of electrons which an atom needs to gain lose, or share to obtain a stable structure is
called its valency. The valency of an element predicts the ratios in which it can combine with
other elements. For example, two atoms of hydrogen (valency 1) combine with one atom of
oxygen (valency 2) to form water. Three atoms of chlorine (valency 1) combine with one atom of
aluminum (valency 3) to form AlCl 3.
The table below shows that atoms with the same number of electrons in their outer shell all have
the same valency. Thus all the group IA metals have valency 1, as do the group VIIA elements
(which are known as the halogens).
Reference Manual
Baker Hughes Drilling Fluids
3-8 Revised 2006