The answer is <span>D.when the aim is to show electron distributions in shells. This is because there are some instances when elements don't possess a regular or normal electron configuration. There are those who have special electron configurations wherein a lower subshell isn't completely filled before occupying a higher subshell. It is best to visualize such cases using the orbital notation.</span>
Answer:
6 elements.
Explanation:
99.9% by weight of most living things is made of the six elements: hydrogen, carbon, nitrogen, oxygen, phosphorus, and sulfur (backwards using just the letter abbreviations this spells SPONCH).
Explanation :
The balanced chemical reaction will be,

By the stiochiometry, 3 moles of solid copper(II)oxide react with 2 moles of ammonia gas to give 3 moles of copper metal, 1 mole of nitrogen gas and 3 moles of liquid water.
The states of matter of each elements and compound is,
Copper(II)oxide is in solid state
Ammonia is in gaseous state
Copper metal is in solid state
Nitrogen is in gaseous state
Water is in liquid state