Lakhasly

ISOTOPES OF HYDROGEN

Hydrogen has three naturally occurring isotopes, denoted 1H, 2H and 3H.Department of Chemisty

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Ortho and Para hydrogen

Ortho hydrogen

para hydrogen

Ordinary dihydrogen is an equilibrium mixture of ortho and para hydrogen

Ortho hydrogen

Para hydrogen

The amount of ortho and para hydrogen varies with temperature as:

At 0?K, hydrogen contains mainly para hydrogen which is more stable.IONIC OR SALINE HYDRIDES

o These are stoichiometric compounds of dihydrogen formed with most of the s-block elements which are highly electropositive in character.IONIC OR SALINE HYDRIDES

o These are stoichiometric compounds of dihydrogen formed with most of the s-block elements which are highly electropositive in character.These hydrides conduct heat & electricity though not as efficiently as their parent metals do.

Unlike saline hydrides, they are almost non- stoichiometric, being deficient in hydrogen.Deuterium and its compounds are used as a non-radioactive label in chemical experiments and in solvents for 1H-NMR spectroscopy.20

Department of Chemisty

COVALENT OR MOLECULAR HYDRIDE

Dihydrogen forms molecular compounds with most of the p-block elements.????????????????????????????????????????????????????

ISOTOPES OF HYDROGEN

Hydrogen has three naturally occurring isotopes, denoted 1H, 2H and 3H.

Protium-one proton () and no neutrons; mass number = 1.

Deuterium-one proton () and one neutron (); mass number = 2

Tritium-one proton () and two neutrons (); mass number = 3

قسم الكيمياء Department of Chemistry

12

1H

1H is the most common hydrogen isotope with an abundance of more than 99.98%.

Because the nucleus of this isotope consists of only a single proton, it is rarely used formal name protium.

قسم الكيمياء

13

Department of Chemistry

2H

21, the other stable hydrogen isotope, is known as deuterium and contains one proton and one neutron in its nucleus.

Deuterium is not radioactive, and does not represent a significant toxicity hazard.

Water enriched in molecules that include deuterium instead of normal hydrogen is called heavy water.

Deuterium and its compounds are used as a non-radioactive label in chemical experiments and in solvents for 1H-NMR spectroscopy.

Department of Chenisby

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Heavy water is used as a neutron moderator and coolant for nuclear reactors. Deuterium is also a potential fu for

commercial nuclear fusion

3H

3H is known as tritium

It contains one proton and two neutrons in its nucleus.

It is radioactive, decaying into helium-3 through beta decay with a half-life of 12.32 years.

قسم الكيمياء Department of Chemisty

15

Ortho and Para hydrogen

Ortho hydrogen

para hydrogen

Ordinary dihydrogen is an equilibrium mixture of ortho and para hydrogen

Ortho hydrogen

Para hydrogen

The amount of ortho and para hydrogen varies with temperature as:

At 0°K, hydrogen contains mainly para hydrogen which is more stable.

At the temperature of liquefaction of air, the ratio of ortho and para hydrogen is 1:1.

At the room temperature, the ratio of ortho to para hydrogen is 3: 1.

Even at very high temperatures, the ratio of ortho to para hydrogen can never be more than 3: 1.

hus, it has been possible to get pure para hydrogen by cooling ordinary hydrogen garto a very low temperature (close to 20 K) but it is never possible to get sample hogen containing more than 75% of ortho hydrogen.

HYDRIDES

• Dihydrogen also forms ionic bonds with some metals, at a high temperature, creating a compound called a hydride.

• If M is the symbol of an element then hydride can be expressed as MHx (e.g. MgH₂) or MmHn (e.g. B2H6).

• The hydrides are classified into three categories: 1.lonic or saline or saltlike hydrides.

2.Covalent or molecular hydrides.

Metallic or non-stoichiometric hydrides.

IONIC OR SALINE HYDRIDES

• These are stoichiometric compounds of dihydrogen formed with most of the s-block elements which are highly electropositive in character.

IONIC OR SALINE HYDRIDES

• These are stoichiometric compounds of dihydrogen formed with most of the s-block elements which are highly electropositive in character.

قسم الكيمياء

20

Department of Chemisty

COVALENT OR MOLECULAR HYDRIDE

Dihydrogen forms molecular compounds with most of the p-block elements. For e.g. CH4, NH3, H2O & HF.

Hydrogen compounds of non metals have also been considered as hydrides. Being covalent they are volatile compounds.

قسم الكيمياء Department of Chemistry

2

METALLIC HYDRIDES

These are formed by many d-block & f-block elements.

The metals of group 7,8 & 9 do not form hydride. These hydrides conduct heat & electricity though not as efficiently as their parent metals do.

Unlike saline hydrides, they are almost non- stoichiometric, being deficient in hydrogen. For LaH2.87 & YbH2.5-