<span>Boron has a lot of different isotopes, most of which having a very short half life (ranging from 770 milliseconds for Boron-8 down to 150 yoctoseconds for boron-7). But the two isotopes Boron-10 and Boron-11 are stable with about 80.1% of the naturally occurring boron being boron-11 and the remaining 19.9% being boron-10. The weighted average weight of those 2 isotopes has the value of 10.81.
The reason they use the average mass of an element for it's atomic weight is because elements in nature are rarely single isotopes. The weighted average allows us to easily compare relative number of atoms of one element against relative numbers of atoms of another element assuming that the experimenters are getting isotope ratios close to their natural ratios.</span>
Answer:
has Two oxygen atoms
Explanation:
Oxygen is a diatomic element hence exists as O2 for majority of its existence in our atmosphere. Although small portion does exist in form of O3 which protects earth from sun's harmful ray, the majority portion of oxygen has O2 which is the oxygen we breathe.
5. 1 hydrogen, 1 Nitrogen, 3 oxygen
<span>To solve this problem, You need to look up a picture/diagram of the electromagnetic spectrum. This will have the wave regions listed as well</span> as frequencies and wavelength.
Wavelength is distance/length of one wave, which can be calculated using frequency (hz = s^-1) and the speed of light.
2.998 x 10^8 m/s ÷ 3 x 10^19 s^-1 = 9.99 x 10^-12 m
The Frequency given falls in between X-rays and Gamma rays. The wavelength however; is in the Gama ray region.
For a closed system, you need two things:
1) a conservation of mass within the boundaries of the system
2) the ability to freely exchange energy to & from the "closed" system with a surrounding external system
So, the answer is <u><em>never</em></u>, since your defining the "system" as the water within the bathtub, and an open bathtub is exposed to evaporation, which is not conserving mass within the defined "system".
