Determine the number of protons and electrons in each ion.(a) Al3+(b) S2?(c) I?(d) Ag+

Solution 82P

Here, we are going to calculate the number of protons and electrons of each ion.

Mass Number: The sum of the number of protons and neutrons in an atom is called its mass number. This is denoted by A.

Atomic number: The number of protons present in the nucleus in an atom is called its atomic number. It is denoted by Z.

We know,

The number of protons and electrons are always same for a neutral atom. Thus, ions are formed by losing or gaining of electrons. A positively charged ion is formed when an atom loses its electron.  So no. of protons always remain same. For example:

Li ------> Li+ + e-

Here, no of protons in Li+ ion will be = 3

But the electrons will  be = 3-1 = 2 e-

Similarly,

A negatively charged ion is formed when atoms gain electrons.

For example : F + e- -----> F-

Total no of protons of F- ion will be same as neutral F,

But the no electrons of F- ion will be = 9+1= 10

(a) Al3+

The number of protons and electrons are always same for a neutral atom.

The atomic number of neutral Al atom Z =13

Thus, no of protons in neutral Al atom = Z =13

Total no. of electrons in neutral Al atom =13

Here,

Al - 3e- ---> Al3+

Here, in ion, no of protons will be same.

Thus, no of protons in Al3+ = 13

Thus, no of electrons in Al3+ = 13-3 = 10 e-

(b) S2-

The number of protons and electrons are always same for a neutral atom.

The atomic number of neutral S atom Z =16

Thus, no of protons in neutral S atom = Z =16

Total no. of electrons in neutral S atom =16

Here,

S+ 2e- ---> S2-

Here, in S2- ion, no. of protons will be same.

Thus, no of protons in S2- = 16

Hence, no of electrons in S2- = 16+2 = 18 e-

(c) I−

The number of protons and electrons are always same for a neutral atom.

The atomic number of neutral I atom Z =53

Thus, no of protons in neutral I atom = Z =53

Total no. of electrons in neutral I atom =53

Here,

I + e- ---> I-

Here, in I- ion, no. of protons will be same.

Thus, no of protons in I- = 53

Hence, no of electrons in I- = 53+1 = 54 e-

(d) Ag+

The number of protons and electrons are always same for a neutral atom.

The atomic number of neutral Ag atom Z =47

Thus, no of protons in neutral Ag atom = Z =47

Total no. of electrons in neutral Ag atom =47

Here,

Ag - e- ---> Ag+

Here, in Ag+ ion, no. of protons will be same.

Thus, no of protons in Ag+ = 47

Hence, no of electrons in Ag+ = 47-1 = 46 e-

The table for the no. of electrons and protons for each ion.