Question

Complete the attached table :

Subject : Chemistry, Class 9
Chapter : Structure of Atoms

Points : 30 ☺

Answer 1

Mass number. Atomic no. No. of protons
============ ========= =============
19. 9. 9
24. 12. 12
35. 17. 17
No. of electrons. Name of the element
============== ===================
9. Fluorine(F)
12. Magnesium(Mg)
17. Chlorine (Cl)

Answer 2

1) mass number =19
we know
mass number =no of protons +no of neutrons
given atomic number = 9
but we know atomic no = no of protons = no of electrons

so,
no of neutrons + 9 = 19
no of neutrons = 10
now,
no of protons = 9
no of electrons =9
name of element =Fluorine (F )

in the same way

2) atomic no = 12
no of electrons = 12
name of element =Magnesium (Mg)

3) atomic no = 17
no of protons = 17
name of element =Chlorine (Cl)