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They should identify the confounding variable.
Some condition that is not examined by the scientist might alter the experiment result. That condition is called confounding variable. If the method of the experiment same but result is very different, there should be unidentified confounding variable. It could be air humidity, temperature, ventilation, light, time of the year or anything that might not be seen by naked eye.
Try to redo the experiment with controlling variable as much as possible.
When a single compound breaks down into two or more compounds or elements in a chemical reaction then it is known as decomposition reaction.
The chemical symbol for sodium carbonate is 
.
The decomposition of sodium carbonate is:
The decomposition of sodium bicarbonate, will result in the formation of sodium oxide, 
and carbon dioxide, 
.
Hence, carbon dioxide, will produce with sodium oxide, on decomposition of .
Isotope ¹⁸F⁻ contains:
1) p⁺ = 9; number of protons.
Fluorine has a<span>tomic number Z = 9 (total number of protons).
2) e</span>⁻<span> = 10; </span>number of electrons.<span>
In element number of electrons and protons are the same, because element has neutral charge, but because in this example, fluorine is anion with negative charge, it has one electron more.
3) n</span>° = 9; number of neutrons.
<span>Mass number
A = 18 is total number of protons and neutrons in a nucleus, so number of neutrons is A-Z = 18-9=9.</span>
In general chemistry, isotopes are substances that belong to one specific element. So, they all have the same atomic numbers. But they only differ in the mass numbers, or the number of protons and neutrons in the nucleus. In a nutshell, they only differ in the number of neutrons.
For Nickel, there are 5 naturally occurring isotopes. Their identities, masses and relative abundance are listed below
Isotope Abundance Atomic Mass
Ni-58 68.0769% <span>57.9353 amu
Ni-60 </span>26.2231% <span>59.9308 amu
Ni-61 </span>1.1399 % <span>60.9311 amu
Ni-62 </span>3.6345% <span>61.9283 amu
Ni-64 </span>0.9256% <span>63.9280 amu
To determine the average atomic mass of Nickel, the equation would be:
Average atomic mass = </span>∑Abundance×Atomic Mass
Using the equation, the answer would be:
Average atomic mass = 57.9353(68.0769%) + 59.9308(26.2231%) + 60.9311(1.1399%) + 61.9283(3.6345%) + 63.9280(0.9256%)
Average atomic mass = 58.6933 amu
