That statement is true
it was easy to organize 'all' the elements in a group of threes because back then they only knew about 15 - 20 elements
hope this helps
Answer:
Option B is correct.
4
Explanation:
We know that an atom consist of electron, protons and neutrons. Protons and neutrons are present with in nucleus while the electrons are present out side the nucleus.
All these three subatomic particles construct an atom. A neutral atom have equal number of proton and electron. In other words we can say that negative and positive charges are equal in magnitude and cancel the each other. For example, if neutral atom has 6 protons than it must have 6 electrons. The sum of neutrons and protons is the mass number of an atom while the number of protons are number of electrons is the atomic number of an atom.
In given problem we are given with 2 neutrons of helium. We know that the atomic number of He is 2. Thus Mass number of He is,
Number of neutrons + number of proton
2 + 2 = 4
Thus, option B is correct.
The variable that is measured as data in an experiment is 1. the dependent variable.
The variables that are held constant in an experiment are 2. the controlled variables.
The variable that is changed by the experimenter is 5. the independent variable.
A count or measurement recorded during an experiment is 4. quantitative data.
Descriptions or observations during an experiment are 3. qualitative data.
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
