1. The arrangement of the phospholipids that make up the cell membrane is referred to as the 2. A carbon atom has 6 protons but has 7 neutrons this carbon atoms would be called a

 1. phospholipid bilayer 2. This is carbon-13, an isotope of carbon

Explanation:1. Two layers of phospholipid form the membrane, with their hydrophilic ends inwards. The hydrophobic surfaces protect the cell from osmotic changes by isolating the cytoplasm from the environment - except for embedded transport mechanisms for moving ions and molecules in and out as required.

2. C-13 is a rare, stable isotope of carbon, making up about 1% of natural carbon.

An element is defined by the number of protons in the nucleus, because the number of protons is matched by the number of electrons in the nucleus, and it is the electrons that determine chemical properties. Nuclei with more than one proton (i.e. not H) also have neutrons, which have no charge. They assist in keeping the positive protons together in the nucleus and are important for stability. Atoms of an element can have different numbers of neutrons, more than one of which can be stable. This variants are called isotopes. They behave the same chemically, but have some different physical characteristics due to size difference.

There are minimum and maximum limits to the number of neutrons that form stable isotopes. Beyond those limits, the atoms tend to decay through radioactivity. For example C-12 and C-13 are stable isotopes. Another natural isotope C-14 is radioactive.

There is also a limit to the number of protons that can be held together by any number of neutrons. Uranium, with 92 protons, has only radioactive isotopes, but U-238 (146 neutrons) decays much more slowly than U-235 (143)or U-234 (142).

the relative atomic mass of an element is the mass of one atom of that element, relative to 1/12th of the mass of a  1212c atom. to convert to an absolute mass in kg, it is necessary to multiply by  1.661×10−271.661×10−27.

the relative atomic mass is roughly equal to the number of neutrons, plus the number of protons, in the nucleus of the atom.

for elements with more than one stable isotope (different types of nucleus with different numbers of neutrons but the same number of protons), the quoted mass is usually the average mass, weighted by the relative abundance of the different isotopes.