The neutral atom of lead must have 82 protons while ions can have b or less than 82.
The atomic number of an element is the number of protons in the nucleus of the element.
Also, for neutral atoms, the number of protons equals the number of electrons.
In ionic form, the number of protons/electrons of an atom may vary and be different from that of the neutral form.
Positive charges mean that the ion has less proton than its neutral version while negative charges mean that it has more electrons than its neutral version.
Thus, the neutral atom of lead will contain an equal number of protons as the electrons while its ionic form can have more or less than 82 protons.
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The law of conservation of energy states that energy is never created or destroyed only converted.
1a) anion and S-2
1b) cation and Al+3
1c) anion and N-3
1d) cation and Ca+2
Density= mass/volume
= 100/25
density = 4g/ml
Answer : The reaction is endothermic.
Explanation :
Formula used :

where,
= change in temperature = 
Q = heat involved in the dissolution of KCl = ?
m = mass = 0.500 + 50.0 = 50.5 g
c = specific heat of resulting solution = 
Now put all the given value in the above formula, we get:


The heat involved in the dissolution of KCl is positive that means as the change in temperature decreases then the reaction is endothermic and as the change in temperature increases then the reaction is exothermic.
Hence, the reaction is endothermic.