Take a one dimensional string of electron-positron pairs. Tie a knot in it. This is a neutron. Without an accompanying proton to balance it's spin due to it's shape, it naturally decays into a proton or hydrogen, which is a balanced state.

Due to its positive charge, a proton requires an electron to be able to export the 'wobble' created by it's shape as it spins. The electron shell provides a balance against the 'epo sea' as describe by D.L. Hotson in his revival of the Dirac Equation.

However, in binding with another proton to form deuterium, one electron is bound with it's accompanying 'shell' and charge back to the proton to create a neutron as it bonds with the second proton. The result is the unbalanced shape of proton turned neutron now has been stablized by the proximity of the proton's net positive charge. The proton still retains it's electron shell, but as it shares it's net positive charge to stablize the neutron, the neutron in turn shares the energy from it's now bound electron shell to make up for the net energy potential difference. This accounts for the stronger covalent bonding than with regular light hydrogen.

The quark model for deuterium:



The charge condensed epo model for deuterium:



Notice how the neutron now has a stable and balanced charge of 2 postive and 2 negative ended 'epos' in the electron-positron string? The bonded proton still retains its net positive charge, but shares this charge and momentum with the neutron to balance out it's 'wobble' due to it's triangular shape.