The specific charge of a particle is given by

$$ \text{specific charge} = \frac{Q}{m} $$

The specific charge of an electron is

$$ \text{specific charge of electron} = \frac{-e}{m_e} $$

$$ \text{specific charge of electron} = \frac{-1.6 \times 10^{-19}}{9.11 \times 10^{-31}} $$

$$ \text{specific charge of electron} = -1.76 \times 10^{11} \text{ C/kg} $$

The specific charge of an proton is

$$ \text{specific charge of proton} = \frac{+e}{m_p} $$

$$ \text{specific charge of proton} = \frac{+1.6 \times 10^{-19}}{1.67 \times 10^{-27}} $$

$$ \text{specific charge of proton} = 9.58 \times 10^{7} \text{ C/kg} $$

If an atom of Chlorine-35 gains one electron what is its specific charge?

The specific charge of the ion is

$$ \text{specific charge of ion} = \frac{-e}{17m_p + 18m_n} $$

$$ \text{specific charge of ion} = \frac{-1.6 \times 10^{-19}}{35 \times 1.67 \times 10^{-27}} $$

$$ \text{specific charge of ion} = -2.74 \times 10^{6} \text{ C/kg} $$

The specific charge of a muon is

$$ \text{specific charge of electron} = \frac{-e}{m_\mu} $$

$$ m_\mu = 1.88 \times 10^{-28} \text{ kg} $$

$$ \text{specific charge of electron} = \frac{-1.6 \times 10^{-19}}{1.88 \times 10^{-28}} $$

$$ \text{specific charge of electron} = -8.51 \times 10^{8} \text{ C/kg} $$

Worth noting the electron has the highest specific charge of any free particle.