Question

the atomic mass of an element is 19 the second shell of its atom contains 7 electrons then the number of neutrons are​

Answer 1

Here's your answer:

The atomic mass of FLUORINE is 19.

FLUORINE contains 7 electrons in its second shell.

9 is the number of neutrons present in FLUORINE.

HOPE IT HELPS........

Answer 2

The numbers of neutrons are 10.

• The first shell which is 1s shell contains 2 electrons. The second shell can contain 8 electrons but this atom contains 7 electrons in its second shell, its electronic configuration is given as-
• ${1s}^{2} {2s}^{2} {2p}^{5}$
• Hence it has a total of 2+2+5=9 electrons.
• Thus the number of the proton is also 9.
• The mass number is 19.
• So, the number of neutrons will be 19-9=10 as the mass number of an atom is a sum of the number of protons and the number of neutrons.