Answer is: 2) A positively charged nucleus is surrounded by mostly empty space.
Rutherford theorized that atoms have their charge concentrated in a very small nucleus.
This was famous Rutherford's Gold Foil Experiment: he bombarded thin foil of gold with positive alpha particles (helium atom particles, consist of two protons and two neutrons).
Rutherford observed the deflection of alpha particles on the photographic film and notice that most of alpha particles passed straight through foil.
That is different from Plum Pudding model, because it shows that most of the atom is empty space.
To calculate the percent
of the radioactive isotope rhenium after 3 half-lives is
(1/2)^3 = 0.125 x 100 =
12.5%
We calculate that there
is 12.5% percent activity of the radioactive isotope.
<span>Radioactive isotope
other called as radioisotope, radioactive nuclide or radionuclide, in any of
the several species of the same chemical element with different masses whose
nuclei are unstable and dissipate excess energy by spontaneously emitting
radiation in the form of gamma, alpha and beta rays. Rhenium is a chemical element
and has an atomic number of 75. Its chemical symbol is Re. It is in the
third-row transition metal in group 7 of the periodic table.</span>
I think E sorry if I’m wrong
Answer:
A mole is the amount of pure substance containing the same number of chemical units as there are atoms in exactly
12 grams of carbon-12 (i.e., 6.023 X 1023).
Explanation:
I believe it is D, as things are passing through