Answer 1)
True
Explanation : To achieve an octet state in valence energy level, an oxygen atom will gain two electrons because as per the definition of octet rule, "The atoms<span> of mainly main-group elements tends to get combined in such a way that each </span>atom gets eight electrons in its last valence<span> shell, giving it the nearest same </span>electron<span> configuration as a noble gas". </span>
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</span>So, in the case of oxygen which has 8 electrons and it will accommodate 2 electrons in its first shell and rest 6 in its last valence shell. In order to achieve the octet state it's easier for the atom to gain 2 electrons rather than giving up rest 6 electrons. Hence, it is true that it gains 2 electrons to complete the octet state.
Answer 2)
True
Explanation : The electronic configuration of Krypton [Kr] is
The abbreviated form of any element can be written as the nearest noble elemental configuration, along with the remaining extra distributed electrons in other orbitals;
Hence, the electron configuration of Cesium [Cs} is
which can be also written as Cs = [Kr]
Break down in to tiny prices as the water hit the tree
False.
Heat speeds up the motion of particles when it is added to the object/substance the atoms loosen up and move/vibrate faster and more. But when subtracting heat from the object/substance, the atoms move/vibrate slower. This is called the Kinetic theory of matter.
1.1 / 2 = .7 --> 2.86 yrs
.7 / 2 = .45 —> 5.72 yrs
.45 / 2 = .225 —> 8.58 yrs
.225 / 2 = .1125 —> 11.44 yrs
So, for the sample of plutonium to reach .140 mg it should take a little less than 11.44 years.
Hope this helps