Me on i'll mark !
oxygen has three isotopes: o16 , o17 , and o18 . in any given sample, 99.757% is o16 , 0.038% is o17 , and 0.205% is o18 . the atomic mass of each is as follows: o16=15.995 amu ; o17=16.999 amu ; o18=17.999 amu .
what is the average atomic mass of oxygen?
a) 15.995 amu
b) 15.999 amu
c) 16.060 amu
d) 16.099 amu

15.999amu

Explanation:

There is way more O16 than any other, so O17 and O18 affect it very little.

2h2o2--> 2h2o + o2

this reaction is of the spontaneous decomposition of hydrogen peroxide down into water and oxygen.

add 2 molecules of hydrogen peroxide and 2 molecules of water. since oxygen is naturally diatomic, the total number of atoms of each element is now the same on both sides of the equation so it is balanced.

this may not be entirely correct but let me know.

metals are good conductor of electricity. it has free electrons on their surface. according to electron pool theory, each atom present in a metal crystal losses all of its valence electron and as a result a pool of free is form. these pool of electrons are free to move and   conduct electricity easily   while making metal as good conductor.

the correct answer is a. the ability of electrons to flow throughout the metal.

if it's not useful, feel free to report for mistake in answer.