Final answer:
The neutron is the subatomic particle that has appreciable mass and lacks a charge.
Step-by-step explanation:
The subatomic particle that has appreciable mass and lacks a charge is the neutron. Neutrons have a mass of 1.0087 atomic mass units (amu) and a charge of zero, making them neutral. In comparison, a proton has a mass of 1.0073 amu and a charge of 1+, while an electron has a much smaller mass of 0.00055 amu and a charge of 1-.