Question

What is the mass number of the particle emitted from the nucleus during beta minus decay? What kind of charge does the particle emitted from the nucleus during beta minus decay have?

Answer 1

Beta decay is exclusively the emission of electrons ... or its
oppositely charged relative, the positron ... from an atomic
nucleus.

Beta-minus is the emission of an electron, with a negative charge.

The change in the mass of the nucleus, if any, is minuscule. 
The mass number of a nucleus is the sum of its protons and
neutrons, and the mass of an emitted electron is something
like 0.0005 the mass of one of those.