Electrons in an atom are found on different electron shells depending on how much energy they possess, and they determine how atoms will interact with each other. The outermost electron shell holds the valance electrons.
Answer: Scientific notation- 
Explanation: I got this by moving the decimal, so that there is one non-zero digit to the left of that decimal point. Tip- The number of decimal places you move will be the exponent on the 10.
Moved right- Negative
Moved left- Positive
Answer: option <span>A) increases from bottom to top within the group.
Explanation:
</span>It is a known trend that the metallic character of the elements increase from let to right and from top to bottom.
The greater the metallic character the greater the reactivity of the metal.
So, the elements of the columns 1 and 2 are the most reactive metals and among them the elements at the bottom are yet more reactive.
<span>The higher reactivity of the metals that are lower in the periodic table is attributed to the greater total number of electrons.
The greater the total number of electrons the more reactive the metals
as their outermost electrons (the valence electrons which are those that react) are located further from the nucleus and therefore they are held less
strongly, which makes them react more easily.</span>
If copper is heated with iron oxide there is no obvious reaction because
copper is less reactive than iron.
On a reactivity chart, copper is far below iron. This makes it impossible for a replacement reaction to occur, so the equation doesn't change.
I hope I helped!
