Uranium, Radium and Radon: Teacher Answer Key
Element
Symbol
Atomic
Number
Atomic
Mass
Atomic Structure
Group/Family and
Properties
Uranium
U
92
238
Protons: 92
Electrons: 92
Neutrons: 330
Part of the actinide series;
silvery white, weakly
radioactive
metal
Radium
Ra
88
226
Protons: 88
Electrons: 88
Neutrons: 138
Alkaline earth metal;
naturally radioactive,
silvery-white metal
that blackens when
exposed to air
Radon
Rn
86
222
Protons: 86
Electrons: 86
Neutrons: 136
Noble gas; colorless,
odorless, and tasteless
radioactive
element
1. How are we exposec
to these elements?
Natural (background) sources: Uranium, radium and radon are naturally occurring radioactive
elements found in soil, rock and water.
Man-made sources: Man-made activities, like digging and mining, can bring these elements to
the surface. These elements may also be found in radioactive waste from human activities like
mining, milling and nuclear power generation.
2.	What is the connection between the elements in the table above?
Uranium decays to form radium and radon. Exposure to radon can cause lung cancer.
3.	Explain how the elements' atomic structures relate to their radioactive properties.
An atom is unstable (radioactive) if the forces among the particles that make up the nucleus are
unbalanced from an excess of either neutrons or protons. Unstable nuclides of any element can
exist. However, almost all elements that are heavier than bismuth, which has 83 protons, have
an unstable nucleus; they are radioactive and are known as "heavy nuclides."
4.	Why is exposure to these elements a concern?
These elements tend to pose more of a concern when they exist in high concentrations (e.g., in
radioactive waste) rather than in their natural state. Concentrations of these elements can
contaminate the soil, water and air. People and animals may also be contaminated by or
exposed to these elements. Exposure to these elements may pose health effects. For example,
radon can cause lung cancer.
v>EPA
United States	RadTown Uranium Activity Set	EPA 402-B-19-072
Environmental Protection
Agency	https://www.EPA.gov/RadTown/Activity-l-Uranium-Radium-and-Radon

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