Explanation:
1) Initial mass of the Cesium-137=
= 180 mg
Mass of Cesium after time t = N
Formula used :
Half life of the cesium-137 =
= initial mass of isotope
N = mass of the parent isotope left after the time, (t)
= half life of the isotope
= rate constant

Now put all the given values in this formula, we get
Mass that remains after t years.

Therefore, the parent isotope remain after one half life will be, 100 grams.
2)
t = 70 years


N = 35.73 mg
35.73 mg of cesium-137 will remain after 70 years.
3)


N = 1 mg
t = ?

t = 224.80 years ≈ 225 years
After 225 years only 1 mg of cesium-137 will remain.
B. Nuclear fission reactions are slowed down as well.
Neutron moderation is a substance which slows down neutron. In some reaction moderator is same as coolant.
This is also used to slow down nuclear fission reaction and continue chain reactions.
The collision between neutron and nuclei is more elastic and more neutrons will be slowed due to size of the neutron.
Learn more at brainly.com/question/24371385
Fe because oxidation mean loss of oxygen and Fe lose the oxygen so Fe is oxidised
The tiny holes in a sponges outer layer that take in water are called ostia, I believe. Hope it helps
Atomic size decreases in a period but the ionization energy and electronegativity increases across a period.
<h3>
Describe the trends in the atomic size, ionization energy and electronegativity?</h3>
Atomic radius decreases across a period because of nuclear charge increases whereas atomic radius of atoms generally increases from top to bottom within a group because there is again an increase in the positive nuclear charge.
Ionization energy increases when we move from left to right across an period and decreases from top to bottom.
Electronegativity also increases from left to right across a period and decreases from top to bottom.
So we can conclude that atomic size decreases in a period but the ionization energy and electronegativity increases across a period.
Learn more about Electronegativity here: brainly.com/question/24977425
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