Answer:

Explanation:
Atomic number : It is defined as the number of electrons or number of protons present in a neutral atom.
However, when we talk about the atomic number of the ion, it is not equal to the number of electrons as electron can be gained or loosed.
This is why, more appropriately, the number of the protons which are present in the nucleus of the atom is called the atomic number.
Thus, atomic number of phosphorus = 15
Mass number is the number of the entities present in the nucleus which is the equal to the sum of the number of protons and electrons.
Given, Mass number = 32
Thus, the symbol of the isotope is:-

Answer:
1) Endothermic.
2)
3)
Explanation:
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1) In this case, for these calorimetry problems, we can realize that since the temperature decreases the reaction is endothermic because it is absorbing heat from the solution, that is why the temperature goes from 22.00 °C to 16.0°C.
2) Now, for the total heat released by the reaction, we first need to assume that all of it is released by the solution since it is possible to assume that the calorimeter is perfectly isolated. In such a way, it is also valid to assume that the specific heat of the solution is 4.184 J/(g°C) as it is mostly water, therefore, the heat released by the reaction is:
3) Finally, since the enthalpy of reaction is calculated by dividing the heat released by the reaction over the moles of the solute, in this case NH4Cl, we proceed as follows:

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They are made of different color of waxes
It showed that atoms can be divided into smaller parts.
It showed that all atoms contain electrons.
Explanation:
The experiment carried out by J.J Thomson on the gas discharge tube by passing electric current through a tube filled with many different gases provided a good insight into the structure of an atom.
This experiment led to the development of the plum pudding model of the atom.
- Cathode rays and it properties were discovered in this set up.
- It furnished the scientific community with evidences that atoms can be divided into smaller parts.
- Since atoms now contain some subatomic particles, they can be broken down in like manner into further bits.
- The cathode rays which were later termed electrons became a fundamental particles known for every atom.
learn more:
Rutherford's model of the atom brainly.com/question/1859083
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