Civil Engineering Reference
In-Depth Information
Figure 4.1: The periodic table.
Radioactivity
In the largest atoms there is often a large inner tension. They want to be radioac-
tive and thereby emit radiation into their surroundings. There are three different
forms of radiation: alpha, beta and gamma radiation. Gamma radiation is pure
electromagnetic radiation and is part of the nucleus of the atom. It can penetrate
most materials in just the same way as X-rays. Alpha and beta radiation come
from particles and are caused by the atom breaking down, reducing the size of
the nucleus. Radium (Ra) with the atomic number 88, will go through a great
number of changes and finally become lead (Pb) with the atomic number 82. This
process takes thousands of years.
Weights of the different substances in a chemical reaction
For a chemical reaction to take place, substances must have the necessary affini-
ty with each other, and be mixed in specified proportions. Only certain sub-
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