Answer : Option 1) nuclei of 
and nuclei of 
only.
Explanation : Radiation is spontaneously emitted from nuclei of 
because this isotope of hydrogen is highly radioactive as compared to other isotopes of hydrogen namely; nuclei of and nuclei of .
They have much stable nucleus as compared to nuclei of .
The more it is unstable the more radiations will be emitted from its nucleus.
Answer:
It is present in third period that's why its valance electrons are present in 3rd energy level.
Its atomic number is greater than lithium when compared in group wise.
There are more electrons in sodium to shield the outer valance electron thus nuclear attraction becomes weak and size increase.
Explanation:
The size of sodium is greater than lithium because atomic number of sodium is 11 and lithium is 3. Both are present in first group but sodium is present down to the lithium. As we move from top to bottom in a group atomic size increases with addition of electrons. The nuclear effect become weaker on valance electrons and atomic size increase. Same time shielding effect is also produces which shield the outer electrons from the influence of nucleus. While in case of lithium less electrons are present to shield the valance electrons.
As we note the position of both elements along period. The sodium is present in third period while lithium is present in second period. So, in case of sodium third energy level is involved. That's why its size is greater than lithium.
Answer: Option (A) is the correct answer.
Explanation:
A phenomenon where delocalization of pi electrons or non-bonding electrons takes place is known as resonance.
For example, in a 
molecule two oxygen atoms contain -1 charge. And, delocalization of pi electrons takes place in order to attain stability.
When in a molecule, there occurs unequal sharing of bonding electrons by a chain of atoms then there occurs a permanent dipole moment. And, this effect is known as inductive effect.
So, basically more difference in electronegativity of the atoms in a molecule tend to cause inductive effect.
In , there is not much difference in the electronegativity of carbon and oxygen atom.
Hence, resonance effect predominates inductive effect.
Potential energy is the energy obtained by an object due to its position.
Thus, we can conclude that the ion is stabilized by resonance.
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Answer:
ΔHrxn = -635.14kJ/mol
Explanation:
We can make algebraic operations of reactions until obtain the desire reaction and, ΔH of the reaction must be operated in the same way to obtain the ΔH of the desire reaction (Hess's law). Using the reactions:
(1)Ca(s) + 2 H+(aq) → Ca2+(aq) + H2(g) ΔH = 1925.9 kJ/mol
(2) 2H2(g) + O2 g) → 2 H2O(l) ΔH = −571.68 kJ/mole
(3) CaO(s) + 2 H+(aq) → Ca2+(aq) + H2O(l) ΔH = 2275.2 kJ/mole
Reaction (1) - (3) produce:
Ca(s) + H2O(l) → H2(g) + CaO(s)
ΔH = 1925.9kJ/mol - 2275.2kJ/mol = -349.3kJ/mol
Now this reaction + 1/2(2):
Ca(s) + ½ O2(g) → CaO(s)
ΔH = -349.3kJ/mol + 1/2 (-571.68kJ/mol)
<h3>ΔHrxn = -635.14kJ/mol</h3>
