A Beta Particle is <span>a fast-moving electron emitted by radioactive decay of substances.</span>
Answer:
Explanation:
scheelite is CaWO₄
Mol weight = 288
80 g of scheelite = 80 / 288 = 27.77 x 10⁻² moles
27.77 x 10⁻² moles of scheelite = 27.77 x 10⁻² x 6.02 x 10²³ molecules of scheelite
= 167.17 x 10²¹ molecules of scheelite
1 molecule of scheelite contains 4 atoms of oxygen
167.77 x 10²¹ molecules of scheelite contains 4 x 167.77 x 10²¹ atoms of oxygen .
= 671.08 x 10²¹ atoms of oxygen .
= 671 x 10²¹ atoms .
Answer:

Explanation:
A radioactive isotope is an isotope that undergoes nuclear decay, breaking apart into a smaller nucleus and emitting radiation during the process.
The half-life of an isotope is the amount of time it takes for a certain quantity of a radioactive isotope to halve.
For a radioactive isotope, the amount of substance left after a certain time t is:
(1)
where
is the mass of the substance at time t = 0
m(t) is the mass of the substance at time t
is the half-life of the isotope
In this problem, the isotope is uranium-235, which has a half-life of

We also know that the amount of uranium left in the rock sample is 6.25% of its original value, this means that

Substituting into (1) and solving for t, we can find how much time has passed:

Answer: No
Explanation:
Example , Mercury is a Liquid metal