How many electron, proton and neutron …

    The information given about the element is 19×9. It means that 19 is the atomic mass whereas 9 is the atomic number of the element.
    The element with atomic number 9 is fluorine. The number of sub-atomic particles present in Fluorine is as follows:

Number of Protons = Number of Electrons = Atomic number  

∴ Atomic number of Fluorine = 9

Number of protons = 9

Number of Electrons = 9

Number of neuton = Mass number - Atomic number

∴ Mass number of Fluorine = 19, Atomic number =9

Number of neutron = 19 - 9 = 10

    As fluorine has 9 electron, the electronic distribution is 2,7. There are seven valence electron present in the outermost shell.
    As valence electron is above 4, therefore valency is 1 (Valency = 8-valence electron).

Conclusion:

Number of electrons = 9

Number of protons = 9

Number of Neutrons = 10

Valency of the element = 1