Chemical bond

Chemical bond is a strong force of attraction that connects atoms in a … or crystal. Usually chemical bonds have …. that is equal to 10000 kJmol ^-1 . There are two types of chemical … . The first type is ionic … . Transfer of electrons … ionic bond. For instance, calcium atom has electron configuration of [Ar] 4s². It has two electrons in outer shell. The electron … of chlorine atom is [Ne] 3s²3p⁵ with seven outer electrons. If calcium atom transfers two …. to chlorine atom it becomes Ca²⁺ ion with stable configuration of inert … . … electrons form covalent bond. … bond is a bond where one of the atoms supplies two electrons. For instance, hydrogen … have one outer electron. In hydrogen molecule H₂ each atom … one electron to the bond. So, hydrogen atom controls two electrons. In water molecule H₂O oxygen atom with six outer electrons controls an extra two electrons which hydrogen atoms supply. Similarly, hydrogen atoms gain control of an extra electron from oxygen.

Notes to the text:

chemical bond – химическая связь

force - сила

attraction - притяжение

electron transfer – перенос электронов

to be equal to - равняться

outer - внешний

shell - оболочка

for instance -например

inert gas - инертный газ

to gain control of - получать контроль над

to supply - давать, обеспечивать

2. Grammar and spelling quiz: find and correct the mistakes in the following sentences:

1. Are alkali metals elements to an group 1 (formerly IA) with pireodec tabl: lithum (Li), sadium (Na), potasium (K), rubium (Rb), cesiem (Cs) and franceum (Fr).

2. Decomposes nitrate lithim wth the oxide.

3. All is high reactive.

4. Are the salts soluble gebneraly.

5. Nitrates decomoposes to give thee oxide.

6. In fact lithum show a number of dissimilarities.

3. Chemical quiz: Are these sentences true or false?:

1. Na is a non-metal.

2. Alkaline-earth metals and alkali metals are similar.

3. Graphite is a metal.

4. The boiling point of carbon is 43 ^o C.

5. C

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   hemical bond is a connection between two chemical elements.

6. Hydrogen atoms controls one molecule.

Exercise 7. Put the prepositions into the gaps, some prepositions can be used 2-3 times: down, with, of, in, on, at, to, of.

1. All the elements react … water (lithium slowly; the others violently) and tarnish rapidly … air.

2. They can all be made to react … chlorine, bromine, sulрhur, and hydrogen.

3. The hydroxides … the alkali metals are strongly alkaline and do not decompose … heating.

4. The carbonates decompose … high temperatures.

5. The energy …..chemical bond is equal … 10000 kJ/mol.

6. The stability of the salts of oxo acids increases … the group.

7. This phenomenon can be observed only … high pressure.

8. One can see an increase … atomic and ionic radius.

9. The standard electrode potentials depend … ionization energy.

10. The larger cations … the bottom … the group tend to polarize less effectively than smaller ones.

11. … fact lithium shows a number … dissimilarities … the other members of group 1.

Exercise 8.

1. Describe any alkali element on the following plan:

1. boiling point;

2. melting point;

3. atomic number;

4. relative density;

5. valence;

6. Is it a metal or non-metal ?;

7. What group does it belong to?;

8. colour;

9. odour;

10. Where is it used?;

11. What substances does it react with?;

12. What chemical compounds does it have?.

2. Choose any two alkali elements and compare them on the following plan using comparative and superlative degree:

1. melting point;

2. boiling point;

3. relative density;

4. atomic and ionic radius;

5. relative atomic mass

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