The simple trick which one can consider in such problem where it is asked for positron emission is :
<span>When the atomic number goes DOWN by one and mass number remains unchanged, then a positron is emitted.
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<span>a. </span>

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Here the atomic number decreases by one.
Similarly, options b and d are eliminated.
Option c is also not the answer.
For c, Count the atomic number on left side and compare it with right side. You will see it is 9 on left and 8 on right. Atomic no. did go down by 1. But the atomic mass is changed as well.
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O2 gas, where there are two Oxygen atoms which are covalently bonded together
<span>rutherfordium element # 104</span>
Answer:
4 & 5 have the same number of elements
Answer:
All elements are neutral
Explanation:
The plum pudding model of the atom indicated that all elements are neutral. The model was proposed by J.J Thomson after he conducted his experiment on the gas discharge tube.
From the experiment he discovered electrons which he called cathode rays.
Therefore, he suggested the plum pudding model of the atom.
The model describes negatively charge sphere surrounded by positive charges to balance them.