Question
Complete the following table.
Elements Atomic number Mass number Protons Electrons neutrons Electronic configuration Valency
Chlorine $17$ ___ ___ ___ $18$ ___ ___
Silicon ___ $28$ ___ $14$ ___ ___ ___
Fluorine ___ ___ $9$ ___ $10$ ___ ___

Answer

Elements Atomic number Mass number Protons Electrons neutrons Electronic configuration Valency
Chlorine $17$ $35$ $17$ $17$ $18$ $2, 8, 7$ $1$
Silicon $14$ $28$ $14$ $14$ $14$ $2, 8, 4$ $4$
Fluorine $9$ $19$ $9$ $10$ $10$ $2, 7$ $1$
Chlorine atomic number is $17$ so protons $=$ electrons $=17$ since number of protons/electrons in an atom determine the atomic number. Mass number will be sum of protons and neutrons $=17+18=35$.
Since the atomic number is $17$ for chlorine so electronic configuration is $2,8,7$. Valency is $1$ .
Silicon atomic number is $14=$ number of electrons/ protons. Since the mass number is $28$ so the number of neutrons is a mass number - the number of protons $=28-14=14$.
The electronic configuration will be $2,8,4$ and valency is $4$ .
Fluorine atomic number is $9=$ number of protons/ electrons. Mass number is $9+10=19$. Electronic configuration is $2, 7$ and valency $1.$

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