You have to do a report :

So
the truck efficiency is 38%.
Answer:
1. hydrogen - H
2. helium - He
3. sodium - Na
4. magnesium - Mg
5. potassium - K
Explanation:
Hydrogen is the element of group 1 and first period. The atomic number of hydrogen is 1 and the symbol of the element is H.
The electronic configuration of the element hydrogen is:-

Helium is the element of group 18 and first period. The atomic number of helium is 2 and the symbol of the element is He.
The electronic configuration of the element helium is:-

Sodium is the element of group 1 and third period. The atomic number of sodium is 11 and the symbol of the element is Na.
The electronic configuration of the element sodium is:-

Magnesium is the element of group 2 and third period. The atomic number of magnesium is 12 and the symbol of the element is Mg.
The electronic configuration of the element magnesium is:-

Potassium is the element of group 1 and forth period. The atomic number of potassium is 19 and the symbol of the element is K.
The electronic configuration of the element potassium is:-

Answer:
They are pollinators of alfalfa.
Explanation:
Without them crops wouldn't be here.
The correct option is this: SODIUM IS VERY REACTIVE BECAUSE IT DOES NOT HAVE A FULL VALENCE SHELL.
For an atom to attain an octet form, it must have eight electrons in its outermost shell. Elements with eight electrons in their outermost shells are un-reactive. Sodium has only one electron in its outermost shell, this makes it to be very reactive because it is very willing to react with suitable elements in order to become stable.
Answer:
8700
Explanation:
First, do the operations i<em>nside parentheses</em>.
102 900/12 = 8600 2 sfs because of 12
170/1.27 = 130 2 sfs because of trailing 0 in 170
===============
Now, do the addition.
8600
<u> + </u><u>13</u><u>0
</u>
8700
The answer has two significant figures because when adding, you must round your answer to the same "place" as the measurement with its last significant figure furthest to the left.
The last significant figure in 8600 (the 6, in the hundreds place) is further to the left than the last significant figure in 130 (the 3, in the tens place).
We round off to the nearest hundred and get the answer, 8700.