Let's eliminate these one by one.
The first pair would not be the same, as X would most likely be in group IA, and Y would be in group VIIA, because of their tendency to gain and lose electrons.
The second pair would also violate the same rule, but X would most likely be in group IIA, and Y would most likely be in group VIA.
The third pair would not be the same, as X is most likely in group VIIA, and since Y has eight valence electrons, it is most likely a noble gas.
The final pair has X with atomic number 15, making it phosphorous. Phosphorous wants to gain 3 electrons to have a full octet of 8 outer "valence" electrons, and Y would also like to gain 3 electrons. This means it is possible that the final pair would be in the same group.
Oxygen: 16.00 g/mol
Hydrogen: 1.01 g/mol
The mass would be 17.01 g/mol
<span>The scientists discovered that when they organized elements in order of increasing atomic mass there is a pattern of repetition of properties (A). The periodic law was developed by Dmitri Mendeleev and Lothar Mayer in 1869. They worked independently of each other and both created a periodic table. They both arranged the items on the table by weight and both suggested that certain properties of the elements recur. The Mendeleev table is the most important table because the values for the atomic mass are the most accurate.</span>
Answer:
B. Ca(OH)2(s)+CO2(aq)-CaCO3(s)+H2O(aq)
This might be right. Im not quite sure. This is what my 5th grade science teacher told me. 'Look at the 2 LR's and add them together. Then look at the total amount which is 32. When you add the 2 LR's you get 17. So subtract 17 from 32 and you get 15. So: C:15 is your answer." (LR's stands for liquid reactants)
10+17=17
Total amount is 32
32-17=15
15 is you mass
Hope this Helps
