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Unit 20
Task 1
Describe using appropriate diagrams and examples:
A, Atomic structure using appropriate scientific terms
Atomic Structure The nucleus, in the center of atom, consist of protons and neutrons.
Orbiting around the nucleus are the electrons.Each unique element has an Atomic Number
equal to the number of protons it contains.
An atom is the smallest constituent unit of ordinary
matter that has the properties of a chemical element.
Every solid, liquid, gas, and plasma is composed of
neutral or ionized atoms. Atoms are extremely small;
typical sizes are around 100 picometers.
B, Alpha, beta and gamma decay using the atomic
model
Alpha Decay
In natural radioactive decay, three common emissions occur. When these emissions were
originally observed, scientists were unable to identify them as some already known particles
and so named them
● alpha particles (αα),αα),
● beta particles, (αα),β)(β), and )(αα),β)(β), and ), and
● gamma rays (αα),γ)(γ) )(αα),γ)(γ) )
using the first three letters of the Greek alphabet. Some later time, alpha particles were
identified as helium-4 nuclei, beta particles were identified as electrons, and gamma rays as
a form of electromagnetic radiation like x-rays except
much higher in energy and even more dangerous to living
systems.
The nuclear disintegration process that emits alpha
particles is called alpha decay. An example of a nucleus
that undergoes alpha decay is uranium-238.
Where does an alpha particle get this symbol? The bottom
number in a nuclear symbol is the number of protons. That
means that the alpha particle has two protons in it which were lost by the uranium atom. The
two protons also have a charge of +2+2. The top number, 4, is the mass number or the total
of the protons and neutrons in the particle. Because it has 2 protons, and a total of 4 protons
and neutrons, alpha particles must also have two neutrons. Alpha particles always have this
same composition: two protons and two neutrons.