Answer:
Summary. To summarize, the periodic table is important because it is organized to provide a great deal of information about elements and how they relate to one another in one easy-to-use reference. The table can be used to predict the properties of elements, even those that have not yet been discovered.
Answer:
the rise and fall is the tides.
OH- is the ion that increases the concentration of a base
and 
.
Assuming complete decomposition of both samples,
First compound:
; 
of the first compound would contain
Oxygen and mercury atoms seemingly exist in the first compound at a 
ratio; thus the empirical formula for this compound would be where the subscript "1" is omitted.
Similarly, for the second compound
; 
of the first compound would contain
and therefore the empirical formula
.
The average atomic mass of an element can be determined by multiplying the individual masses of the isotopes with their respective relative abundances, and adding them.
Average atomic mass of Br = 158 amu(0.2569) + 160 amu(0.4999) + 162 amu(0.2431)
Average atomic mass = 159.96 amu
As described in the problem, the relative abundance for Br-79 is 25.69%. This is because 2 atoms of Br is equal to 79*2 = 158 amu. Similarly, the relative abundance of Br-81 is 81*2 = 162, which is 24.31%.
