Suppose you made up your own 'atom', as Thomson described, using clay for the positive charge and small beads for the electrons spread through it. What will happen if:
the positive charge on the clay is lesser than the total negative charge of the beads?
If the positive charge on the clay is lesser than the total negative charge of the beads, the atom will not be neutral. The positive and negative charges will not stay balanced, resulting in a net negative charge on the atom.
by mistake, the clay itself carries a bit of negative charge? Would your model still represent a neutral atom?
No, the model would not represent a neutral atom. Thomson proposed the atom as a sphere of positive charge with electrons distributed throughout it. If the clay carries a bit of negative charge, the total negative charge increases, disrupting the required balance between positive and negative charges.
Explanation
Thomson's model emphasizes that atoms are neutral, which requires the positive charge of the sphere to perfectly balance the negative charge of the electrons. In part (i), a lesser positive charge means the charges do not stay balanced, leading to a negatively charged atom. In part (ii), if the clay itself is negatively charged, it violates the fundamental premise of Thomson's model (a sphere of positive charge), causing an imbalance and making the atom negatively charged rather than neutral.