The presence of helium gas indicates the radioactive sample is most likely decaying by α-decay, or alpha decay. α-decay is the type of radioactive decay in which an atomic nucleus emits α particles. α particles are Helium nuclei. So the correct answer would be α-decay.
They should look for <span>a report from an independent scientific research firm,
even if they have to pay for it.
In preparing its report, the firm would have already surveyed many of the </span>
<span>citizens from several other towns that currently add fluoride to their water,
plus a lot of other relevant medical research on the subject.</span>
Answer:
Atomic radius decreases moving from left to right across a period.
Explanation:
When we move left to right across a period, the size of atoms generally decreases. It is because within the period the outer electrons are in same valence shell and the number of electrons and proton increases moving from left to right across the the period. It increases the effective nuclear charge resulting in the increased attraction of electron to the nucleus that causes the decreased radius of the atoms.
The similarities and the differences between gravitational and electric force are listed below
Explanation:
- The magnitude of the gravitational force between two objects is given by Newton's law of gravitation:
where
is the gravitational constant
are the masses of the two objects
r is the separation between them
- Coloumb's law gives instead the strength of the electrostatic force between two charged objects, which is
where:
is the Coulomb's constant
are the two charges
r is the separation between the two charges
By comparing the two equations, we find the following similarities:
- Both the forces are inversely proportional to the square of the distance between the two objects,
- Both the forces are proportional to the product between the "main quantity" of each force, which is the mass for the gravitational force (
) and the charge for the electric force (
Instead, we have the following differences:
- The gravitational force is always attractive, since the sign of
is always positive, while the electric force can be either attractive or repulsive, since the sign of 
can be either positive or negative - The value of the gravitational costant G is much smaller than the value of the Coulomb's constant, so the gravitational force is much weaker than the electric force
Learn more about gravitational force and electric force:
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