Isotopes,Isobars and Isotones

 

Calculation of electrons, protons, neutrons:

In this spherical shaped atom nucleus is present in the middle of atom · Neutrons & protons are present in the nucleus so they are called as “nucleons” · Electrons are revolving around the nucleus. In specific circular paths called as shells on orbits

No. of Electrons in an atom = atomic number (z)

No. of protons in an atom = atomic nucleus (z)

No. of neutrons in an atom(n) = A-Z

Isotopes,Isobars and Isotones

Isotopes:

The (same) elements which are having same atomic number but different in their mass numbers.

Isotopes are atoms of the same element with the same number of protons but  different numbers of neutrons.

Examples:

1. Hydrogen:

- Protium-H¹ (1 proton, 0 neutrons)

- Deuterium-H²(1 proton, 1 neutron)

- Tritium -H³(1 proton, 2 neutrons)

 

2. Carbon:

- Carbon-C¹²(6 protons, 6 neutrons)

- Carbon-C¹³ (6 protons, 7 neutrons)

- Carbon-C¹⁴(6 protons, 8 neutrons)

 

3. Oxygen:

- Oxygen-O¹⁶(8 protons, 8 neutrons)

- Oxygen-O¹⁷ (8 protons, 9 neutrons)

- Oxygen-O¹⁸ (8 protons, 10 neutrons)

 

4. Uranium:

- Uranium-U²³⁵ (92 protons, 143 neutrons)

- Uranium-U²³⁸(92 protons, 146 neutrons)

 

5. Chlorine:

- Chlorine-35 (Cl³⁵) - 17 protons, 18 neutrons

- Chlorine-37 (Cl³⁷) - 17 protons, 20 neutrons.

Isobars:

The (different)elements which are having same mass number but different in their

atomic numbers.

(or)

Isobars are atoms of different elements with the same mass number.

 

Examples:

 

1. Carbon-14 (6 protons, 8 neutrons) and Nitrogen-14 (7 protons, 7 neutrons)

 

2. Oxygen-16 (8 protons, 8 neutrons) and Fluorine-16 (9 protons, 7 neutrons)

 

3. Calcium-40 (20 protons, 20 neutrons) and Argon-40 (18 protons, 22 neutrons)

 

4. Potassium-40 (19 protons, 21 neutrons) and Argon-40 (18 protons, 22 neutrons)

 

5. Chlorine-36 (17 protons, 19 neutrons) and Argon-36 (18 protons, 18 neutrons)

 

Isotones:

The (different) elements which are having different atomic numbers and different

mass numbers,but similer in their number of neutrons(n=A-Z).

 

Examples:

 

1. Carbon-13 (6 protons, 7 neutrons) and Nitrogen-14 (7 protons, 7 neutrons)

 

2. Oxygen-17 (8 protons, 9 neutrons) and Fluorine-18 (9 protons, 9 neutrons)

 

3. Neon-21 (10 protons, 11 neutrons) and Sodium-22 (11 protons, 11 neutrons)

 

4. Magnesium-25 (12 protons, 13 neutrons) and Aluminum-26 (13 protons, 13 neutrons)

 

5. Silicon-29 (14 protons, 15 neutrons) and Phosphorus-30 (15 protons, 15 neutrons).

Average atomic mass is the weighted average of the masses of an element's naturally occurring isotopes.

 

Formula: Average atomic mass = (mass of isotope 1 × abundance) + (mass of isotope 2 × abundance) + ...

 

Example 1: Chlorine

 

- Chlorine-35 (mass: 34.97 u, abundance: 75.78%)

- Chlorine-37 (mass: 36.97 u, abundance: 24.22%)

 

Average atomic mass = (34.97 × 0.7578) + (36.97 × 0.2422) = 35.45 u

 

Example 2: Neon

 

- Neon-20 (mass: 19.99 u, abundance: 90.48%)

- Neon-21 (mass: 20.99 u, abundance: 0.27%)

- Neon-22 (mass: 21.99 u, abundance: 9.25%)

 

Average atomic mass = (19.99 × 0.9048) + (20.99 × 0.0027) + (21.99 × 0.0925) = 20.18 u