<Dd> (↑ ↑ ⟩ 1 2 (↑ ↓ ⟩ + ↓ ↑ ⟩) ↓ ↓ ⟩) (\ displaystyle \ left ((\ begin (array) (ll) \ uparrow \ uparrow \ rangle \ \ (\ frac (1) (\ sqrt (2))) (\ uparrow \ downarrow \ rangle + \ downarrow \ uparrow \ rangle) \ \ \ downarrow \ downarrow \ rangle \ end (array)) \ right)) </Dd> <P> and thus consists of three types of nuclei, which are supposed to be symmetric: a deuterium nucleus (actually a highly excited state of it), a nucleus with two protons, and a nucleus with two neutrons . The latter two nuclei are not stable or nearly stable, and therefore so is this type of deuterium (meaning that it is indeed a highly excited state of deuterium). </P> <P> The deuteron wavefunction must be antisymmetric if the isospin representation is used (since a proton and a neutron are not identical particles, the wavefunction need not be antisymmetric in general). Apart from their isospin, the two nucleons also have spin and spatial distributions of their wavefunction . The latter is symmetric if the deuteron is symmetric under parity (i.e. have an "even" or "positive" parity), and antisymmetric if the deuteron is antisymmetric under parity (i.e. have an "odd" or "negative" parity). The parity is fully determined by the total orbital angular momentum of the two nucleons: if it is even then the parity is even (positive), and if it is odd then the parity is odd (negative). </P> <P> The deuteron, being an isospin singlet, is antisymmetric under nucleons exchange due to isospin, and therefore must be symmetric under the double exchange of their spin and location . Therefore, it can be in either of the following two different states: </P>

What element has 2 neutrons and 2 electrons