1. Isotopes: the same element, the same atomic number, but different mass numbers
Atomic mass: the average atomic mass of all its isotopes
The mass of an atom of carbon-12= 12 amu ( atomic mass unit) because it has a stable nucleus
[tex]\tt RAM~X=\dfrac{the~average~mass~of~1~atom~X}{\dfrac{1}{12}\times mass~of~atom~C-12 }[/tex]
So RAM relative to isotopes Carbon-12 (C)
2. Ionic Formula is formed from cation(positive charge) and anion(negative charge)
Cation : Na⁺ ( positively charged 1)
Anion : SO₄²⁻ (negatively charged 2)
The anion cation's charge is crossed , then the compound :
[tex]\tt \boxed{\bold{Na_2SO_4}}[/tex]
3. pH is the degree of acidity of a solution that depends on the concentration of H⁺ ions. The greater the value the more acidic the solution and the smaller the pH.
pH = - log [H⁺]
[H⁺] = 0.00001 M = 10⁻⁵ M
[tex]\tt pH= -log 10^{-5}\\\\pH=5~log~10\\\\pH=\boxed{\bold{5}}[/tex]
