<u>Answer:</u> The electronic configuration of gallium is written below and number of valence electrons is 3.
<u>Explanation:</u>
Electronic configuration is defined as the representation of electrons around the nucleus of an atom.
Number of electrons in an atom is determined by the atomic number of that atom.
Valence electrons are defined as the electrons present in the outermost shell of an atom.
We are given:
An element Gallium having atomic number as 31.
Number of electrons = 31
Electronic configuration of Gallium is: 
This element has 3 electrons in its outermost shell. So, the number of valence electrons is 3
Hence, the electronic configuration of gallium is written below and number of valence electrons is 3.
A theory is a proposed explanation for an observation
PH is defined as the negative log of Hydronium Ion concentration.
So, in order to find the pH of vinegar, we find the negative log of its hydronium ion concentration.
![pH=-log[ H_{3}O^{+}] \\ \\ pH=-log(1.6 * 10^{-3}) \\ \\ pH=2.8](https://tex.z-dn.net/?f=pH%3D-log%5B%20H_%7B3%7DO%5E%7B%2B%7D%5D%20%5C%5C%20%20%5C%5C%20%0ApH%3D-log%281.6%20%20%2A%2010%5E%7B-3%7D%29%20%20%5C%5C%20%20%5C%5C%20%0ApH%3D2.8)
So, the pH of given vinegar solution will be 2.8.
Therefore, the answer to this question is option B
To Find :
The volume of 12.1 moles hydrogen at STP.
Solution :
We know at STP, 1 mole of gas any gas occupy a volume of 22.4 L.
Let, volume of 12.1 moles of hydrogen is x.
So, x = 22.4 × 12.1 L
x = 271.04 L
Therefore, the volume of hydrogen gas at STP is 271.04 L.