A field force is a force that acts equally on all the items in it. For example, the force you exert on the chair when you push it acts only on the chair - not on the table, other chairs, etc. around it. Whereas a force like gravity acts equally on everything - on the apple, on the leaves, on the other apples in the tree, etc
The relationship between H+ ion concentration and pH is pH=-lg[H+]. So the pH of the solution is -lg(1.25*10^-10) = 9.9.
Helium - 4 isotope has 2 protons and 2 neutrons.
Its atomic number is 2 (the number of protons). Atomic number is the number of protons in the atom of an element and it identifies the element. All the isotopes of an element have the same atomic number (same number of protons). So, all the isotopes of hellium have 2 protons.
The number 4 that identifies the helium - 4 isotope is the mass number, i.e. the number of protons plus the number of neutron. So, helium-4 isotope has 2 protons and 2 neutrons. While, other isotopes of helium have 2 protons but different number of neutrons.
The atomic number enable us to deduce the number of electrons in an atom because the atoms are neutral, which implies that the positive and negative charge are equal. Given that the magnitude of the charge of electons and protons are equal but the sign is opposed (protons are positve and electrons are negative) the number of electrons in the atom equals the number of protonts. That is why the atomic number is also the number of electrons of the atom.
One substance can be separated from another through physical means
