Answer:
They have completely filled outermost shell
Explanation:
The noble gases are the rarest and occur in trace amounts in the atmosphere because they have completely filled outermost and this makes them unreactive with other elements.
Elements become abundant as they combine with other species to form compounds.
Noble gases on the other hand have a high level of stability and do not readily combine with other species.
Some of these gases are :
Helium
Neon
Argon
Krypton
Xenon
Radon
They have very high ionization energy and very low electron affinity and so will not readily react.
Answer:
I think it is 100 if I guess
Solution:
The idea of an atom proposed by the Greek philosophers because:
According to Greek Philosopher, matter is composed of small and indivisible particles called atoms. He introduced atoms as too small to be seen, unchangeable, completely solid without internal structure. He proposed that atoms are of variety of shapes and sizes which is responsible for different types of matter.
But according to Dalton’s atomic theory, chemical elements have atoms, which are identical in weight. The different elements have different atoms of different weight. Atoms can combine in whole-number ratios to form compounds. These observations are already introduced by Greek philosopher, but the idea of atomic weight is introduced by Dalton. He introduced the list of 21 elements with their atomic weights and, he was the first to propose the element’s symbol.
Answer:
<u>During Metaphase</u>
<u></u>
Explanation:
During Metaphase the cell chromosome align themselves in the middle of the cell.This occur due to a cellular process called "Tug of War".
The chromosome which have been replicated and joined at the central point called centromere are called sister chromatids
Prior to metaphase , Kinetochore type of protein are formed around the centromere. Long protein filament called kinetochore are extended from poles to other end of the cell attached to kinetochore.
Therse is important checkpoint in the middle of mitosis called<u> metaphase.</u>
At this point cell ensure that , it is ready to divide or not.
Once the cell ensure that everything is ready to divide. Only after then , yhe cell enters the fourth phase called <u>anaphase.</u>
