Answer:
20 electrons
A neutral atom with atomic number 20 will have 20 electrons.
The atomic number is, by definiton, the number of protons in an atom's nucleus but for a neutral atom it's also equal to the number of electrons. Each element has a different, unique number of protons that determines its identity.
Explanation:
Answer : The molar heat of solution of KCl is, 17.19 kJ/mol
Explanation :
First we have to calculate the heat of solution.

where,
q = heat produced = ?
c = specific heat capacity of water = 
= change in temperature = 0.360 K
Now put all the given values in the above formula, we get:


Now we have to calculate the molar heat solution of KCl.

where,
= enthalpy change = ?
q = heat released = 460.8 J
m = mass of
= 2.00 g
Molar mass of
= 74.55 g/mol

Now put all the given values in the above formula, we get:


Therefore, the molar heat of solution of KCl is, 17.19 kJ/mol
Balanced chemical reaction: 2KCl + Pb(NO₃)₂ → PbCl₂ + 2KNO₃.
According to principle of mass conservation, number of atoms must be equal on both side of balanced chemical reaction.
KCl is potassium chloride.
Pb(NO₃)₂ is lead(II) nitrate.
KNO₃ is potassium nitrate.
PbCl₂ is lead(II) chloride.
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<h3>Further explanation
</h3>
Electrons can move the shell up or down by releasing energy or absorbing energy
Excited electrons show higher electron transfer to the shell by absorbing energy
So it can be concluded that there are 2 conditions:
Ground state is the state of electrons filling shell with the lowest energy levels.
Excited state is the state of electrons which occupies a higher energy level
The state of excited electrons can be seen from the presence of electrons which do not fill the skin completely but fill the skin afterward
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From its 8 electron configuration, filling 3 shells, 2 electrons in the firs shell, 7 electrons in the second shell and 1 electron in the third shell
the electrons in the third shell should fill the electrons in the second shell first according to Aufbau rule (lower energy shells)
