Answer: C) Roman numeral following the name.
Explanation: If we want to name an ionic compound like NaCl then we can easily write its name. Na is sodium and Cl is chlorine. First we write the name of the metal ion and then the name of the anion it has. Here we have mono atomic ion and for these we use the suffix -ide. So, the name will be sodium chloride.
Now, if we have something like 
and we write the name as Iron chloride, then it will not be correct since Fe is a transition metal and it shows +2 and +3 oxidation states. So, to overcome this difficulty, a roman numeral is used for the oxidation state of the metal ion. The name of above compound will be Iron(III)chloride. Similarly, if we have 
then its name will be written as Iron(II)chloride.
In both the above names, the roman numerals (III) and (II) are indicating numerical value of the charge of the metal ion. So, the correct choice is C) Roman numerals following the name.
when naming a transition metal ion that can have more than one common ionic charge, the numerical value of the charge can be indicated by a Roman numeral following the name.
Lithium fluoride is the compound name
Answer:
82.1
Explanation:
Isotopes of the same element are atoms of the same element (so, having same number of protons) having a different number of neutrons (and so, a different atomic mass).
In this problem, this element has 3 different isotopes, with atomic mass (in atomic mass units, a.m.u.) and relative abundance listed below:
1) 78.9 12.6%
2) 80.9 13.9%
3) 82.9 73.5%
In order to calculate the relative atomic mass unit of this element, we have to calculate the weighed average of the relative atomic mass of each isotope.
This means that we can calculate it as the sum of each atomic mass unit multiplied by the relative frequency:
where 
is the atomic mass of each isotope and 
the relative frequency. Therefore, we find:
