It has 7 electrons
The atomic number for any element is the number of protons in its atomic nuclei. In a neutral atom, the number of electrons are the same as the number of protons. The atomic mass (mass number) is the sum of the protons and neutrons in the nucleus. Mass number can vary due to the fact that the number of neutrons can vary.
Rubber exists in both forms
I believe it is A because the plant is offering protection while the bacteria is converting it in to nitrogen that the plant can use!
It is used to find the hydrogen ion concentration in a solution i believe