2.998e^8 is how I would write it. If you want it with the least amount of decimals, use 3e^8
Sorry this will probably be pretty long.
So think of the "control" as being something you yourself add to increase or decrease the effects in an experiment.
I'll give you an example so it is not as confusing.
Say you have decided to make an experiment on plants. Which plant can grow the fastest on which type of liquid? What is being added to this experiment? The liquid! Or all of the liquids you used. Like if you used Coke, Lime Gatorade, Orange Gatorade, and Water. Each drink will EFFECT each plant differently.
Hope I was of any hope?
Answer:
(a) (i) All the elements of a group have similar chemical properties because they have same no. of valence electrons in their outermost shell. (ii) All the elements of a period have different chemical properties because they have different no. of valence electrons in their atoms.
<span>Lithium atoms have one valence electron, where as oxygen atoms have six. Lithium atoms tend to give up their single valence electrons, and oxygen tends to gain two valence electrons from other atoms, like lithium. They do this so they will have filled valence shells. hope this answers your question :)</span>