If an atom has 123 protons, and a mass of 256, what is the atomic number of this element? A. 123
B. 256
C. 133
D. None of these​

answer: 2

explanation:

yes

what statement best describes the difference between the sympathetic and parasympathetic nervous systems?

the sympathetic nervous system prepares the body for intense physical activity and is often referred to as the fight-or-flight response. the parasympathetic nervous system has almost the exact opposite effect and relaxes the body and inhibits or slows many high energy functions.

sodium i think the chemical element of atomic number 11, a soft silver-white reactive metal of the alkali metal group.

oxygen = 21% of the atmosphere

nitrogen = 78%

carbon dioxide = 0.1%

argon =0.934%