HYDRIDES

chemistry class 11 std chapter 9 topic 9.5

1. HYDRIDES

2. HYDRIDES

A hydride is any class of chemical compound in which hydrogen is combined
with another element.

Three basic types of hydrides—saline (ionic), metallic, and covalent—may be
distinguished on the basis of type of chemical bond involved.

A fourth type of hydride, dimeric(polymeric) hydride, may also be identified on
the basis of structure.

Aluminum and, possibly, copper and beryllium hydrides are non-conductors that
exist in solid, liquid, or gaseous forms.

All are thermally unstable, and some explode on contact with air or moisture.

3. エー つつ Hee
a hydrogen atom a proton

He 4 8 —. He
a hydrogen atom a hydride ion

4. covalent

EE borderline

HHHHHFHHHHHHHHFH

5. SALINE (IONIC) HYDRIDES

> Saline, or ionic, hydrides are defined by the presence of hydrogen as a
negatively charged ion, H-. The saline hydrides are generally considered
those of the alkali metals and the alkaline-earth metals (with the possible
exception of beryllium hydride, BeH,, and magnesium hydride, MgH,).

> These metals enter into a direct reaction with hydrogen at elevated
temperatures (300-700 °C [570-1,300 °F]) to produce hydrides of the general
formulas MH and MH,.

6. Li Li

+ Hatom

I —
u 1.689 (1.596)
삐 Be

1.402 (1.343) 1.413 (1.334)

13470330 BH,
1.243 (1.207)
1.252 (1.190)

1.744 (1.757)

7. » The hydride ion in the saline hydrides is a strong base,

and these hydrides
(H*) from water to
ion in solution.

react instantly and quantitatively with the hyc
produce hydrogen gas and the

706

H- + H,0 +H, + OH-

Because saline hydrides react vigorously with , giving off large volumes

of gaseous hydrogen, this property renders them useful as light, portable
sources of hydrogen.

8. METALLIC HYDRIDES

> The transition metals and inner transition metals form a large variety of compounds
with hydrogen.

> Metallic hydrides are formed by heating hydrogen gas with the metals or their alloys.

と Metallic alloy like hydrides possess some of the characteristics of metals, such as lust
and strong electrical conductivity. They tend to have variable physical properties, with
some being more brittle and others being harder than the metals from which they are
made.

と Metallic hydrides essentially consist of protons (positive hydrogen ions, H*) and metal
atoms in an electron sea.

9. 2Na
NaH

CaH,

+

2NaH ”一 一 2NaH

A
-一

A

— NaOH + Hg)
A

—

—

GH —> Cam,
Ca(OH), + Hg)

10. COVALENT HYDRIDES

> Covalent hydrides are primarily compounds of hydrogen and non-metals, in
which the bonds are evidently electron pairs shared by atoms of comparable
electronegativities.

> For example, most non-metal hydrides are volatile compounds, 1060
together Il in the condensed state by relatively weak van de S
n ar interactions.

11. methane

H— Cl
Hydrogen chloride

H
|

ammonta

H

H=S
Hydrogen sulphide

12. Covalent hydrides are liquids or gases that have low melting and boiling
points, except in those cases (such as water) where their properties are
modified by hydrogen bonding.
For example, NH。, H,O, and HF are held together in the liquid state
primarily by hydrogen bonding.

The hydrogen compounds formed with the elements that follow oxygen—
HS, H,Se—are all volatile, toxic gases with repulsive odours. They are easily
prepared by adding dilute acid to the corresponding metal su », selenide.

13. (>) Covalent bond (>)

e

Hydrogen bond

14. > Each of the halogens forms a binary compound with hydrogen, HX. At

ambient temperature and pressure, these compounds are gases, with
ydrogen fluoride having the highest boiling point owing to intermolecular
hydrogen bonding.

15. APPLICATIONS

> Hydrides such as so
commonly used as rec

n borohydride, lit
icin ents in cher

> Hydrides such as um hydride and potassium hydride are used as strong

bases in organic s esis. The hydride reacts with the weak acid releasing
H,.
> Hydrides such as calcium hydride are used as drying agents, to remove trace

water from organic solvents. The hydride reacts with water forming
ydrogen and hydroxide salt.

16. > Hydrides are important in storage battery technologies such as

ckel-metal hyd attery.

> Various metal hydrides have been examined for use as a means of hydrogen
storage for cell-powered electric cars and other purposed aspects of a

hydr

Jen ec

17. THANK YOU