Answer:
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Explanation:
PLEASE NOTE; I HAVE WRITTEN THE ATOMIC NUMBER IN BRACKETS, NEXT TO THE SYMBOL OF THE ELEMENT
The early precambrian atmosphere consisted primarily of nitrogen and carbon dioxide with almost no oxygen.
<span>Today, the atmosphere contains about 20% oxygen, less carbon dioxide and similar amounts of nitrogen. </span>
<span>Photosynthetic green-leaf plants and trees are largely responsible for the change, converting carbon dioxide to oxygen.</span>
Answer:
Element Name: Oxygen
Symbol: O
What is the Mass: 15.999 u
Protons: 8
Neutrons:10
Electrons: 8
Ion or Isotope: Oxide
Explanation:
A post-test or a mastery test can be unlocked if the learner who has the of it previously can complete the given tutorial with the test.
After the tutorial with the test, the learner will have to complete everything and if he passes the test with a completed answer then he will see that the Mastery Test has been unlocked. Also after the mastery test is unlocked it can be done again.
