The atomic number of H2O is 18 hence it contains 18 protons. Hope this helps.
Answer:
Protons: 2.
Electrons: 2.
Neutrons: 2.
Explanation:
Hello,
In this case, since an atom's atomic number is equal to the number of electrons, considering the electron configurations, taking into account that helium-4 is neither positively nor negatively charged, we can infer that the number of electrons equal the number of protons, which in this case are 2, due to the fact that is atomic number is 2.
Moreover, as helium-4's atomic number is 4 as a whole number, we compute the number of neutrons by using the shown below equation:

Regards.
From the electric generator to electric outlets in homes
Answer:
highest first ionization energy - Br
smallest atomic size - Br
most metallic character - Na
Explanation:
Ionization energy of Br is higher than P because higher zeff value
Sodium is more metallic than calcium because it is able to loose electron more readily as compared to calcium because of higher electro positivity.
Atomic radius of Br is the smallest as its atomic radius is 114, P (115), Ca (197), Na (186)
It would be MnSO4
The (II) lets you know it’s the form with a 2+ charge and Sulfate has a 2- charge
These will cancel out making it plain MnSO4
If it was manganese (iii) sulfide the answer would be Mn2(SO4)3