Answer: Be= 2, C =4, Li = 1 and B=3
Explanation:
The valence shell can be define as the outermost shell of an atom that contains the valence electrons.
Beryllium (Be), electronic configuration; 1s2 2s2, = 2 electrons in its valence shell.
Carbon (C), electronic configuration; 1s2 2s2 2p2, = 4 electrons in its valence shell.
Lithium (Li), electronic configuration; 1s2 2s1 = 1 electron in its valence shell.
Boron (B) , electronic configuration; 1s2 2s2 2p1 = 3 electron in its valence shell.
Answer: By using electrolysis.
Explanation:
Electrolysis is a chemical change produced by sending an electric current through a compound. Electrolysis works because the hydrogen and oxygen ions are held together by an electric attraction.
Answer:
a solution color becoming less intense due to dilution- is not an evidence of a chemical reaction
bubbles (gas formation) - evidence of a chemical reaction
explosion or fire - evidence of a chemical reaction
changes in color- evidence of a chemical reaction
precipitation- evidence of a chemical reaction
changes in temperature - evidence of a chemical reaction
a solid liquifying - is not an evidence of a chemical reaction
solution colors mixing - is not an evidence of a chemical reaction
Explanation:
A chemical change is not easily reversible and yields new substances. It is often accompanied by a loss or gain of heat.
In the answer section, i have shown some evidences that lead us to conclude that a chemical reaction has taken place. The occurrence of a chemical change often goes with the formation of new substances as earlier stated and any of these signs may accompany the process.
For instance, when a metal is dropped in dilute acid solution, bubble of hydrogen gas indicates that a chemical reaction has taken place.
The given question is incomplete. The complete question is:What is the relative atomic mass of a hypothetical element that consists isotopes in the indicated natural abundances.
Isotope mass amu Relative abundance
1 77.9 14.4
2 81.9 14.3
3 85.9 71.3
Express your answer to three significant figures and include the appropriate units.
Answer: 84.2 amu
Explanation:
Mass of isotope 1 = 77.9
% abundance of isotope 1 = 14.4% = 
Mass of isotope 2 = 81.9
% abundance of isotope 2 = 14.3% = 
Mass of isotope 3 = 85.9
% abundance of isotope 2 = 71.3% = 
Formula used for average atomic mass of an element :
![A=\sum[(77.9\times 0.144)+(81.9\times 0.143)+(85.9\times 0.713)]](https://tex.z-dn.net/?f=A%3D%5Csum%5B%2877.9%5Ctimes%200.144%29%2B%2881.9%5Ctimes%200.143%29%2B%2885.9%5Ctimes%200.713%29%5D)
Therefore, the average atomic mass of a hypothetical element that consists isotopes in the indicated natural abundances is 84.2 amu
