Revision exercises

Ex.1. Answer the following questions:

1. What is a chemical bond caused by? 2. What is bond energy? 3. What are the principal types of a chemical bond? 4. When is an ionic bond formed? 5. How is the polarity of a covalent bond defined? 6. What bond is responsible for the crystalline structure of pure metals? 7.What is the reason of hydrogen bonding?

Ex.2. Match the words with their definitions:

1. attraction	a. a measure of the combining power of an element with other atoms when it forms chemical compounds or molecules;
2. charge	b. a positively charged ion that is attracted to the cathode in electrolysis;
3. valence	c. a protein that functions as a catalyst for a chemical reaction;
4. cation	d. the physical property of matter that causes it to experience a force when placed in an electromagnetic field;
5. bonding	e.a system that uses only two values (as 0 and 1 or yes and no) to represent codes and data;
6.binary system	f. the force attracting atoms to each other and binding them together in a molecule;
7. enzyme	g. an interaction that accounts for the association of atoms into molecules, ions, crystals and other stable species that make up the familiar substance.

Ex.3. Say whether the following statements are true or false:

1. A chemical bond is a region that forms when electrons from different atoms interact with each other. 2. The bond is caused by the electrostatic force of attraction between similar charges. 3. The negatively charged electrons orbiting the nucleus and the positively charged protons in the nucleus repel each other. 3. The atoms in molecules, crystals, metals are held together by chemical bonds which dictate the properties of mater. 4. Covalent bonds are created between ions where one is a metal and one is a non-metal element. 5. The polarity of a covalent bond is defined by any difference in electropositivity. 6. A coordinate covalent bond is formed when one atom donates both of the electrons to form a single covalent bond. 7. Metallic bond is the strongest of the three major bonds because the electrons are shared in more than just the first shells.

Ex.4. Insert the necessary word:

1. The extreme mobility of the electrons in a metal explains its high thermal and electrical ... . 2. Hydrogen bonding does not occur in molecules with nonpolar ... bonds. 3. Chemical bonds allow all of the elements to ... in a variety of ways to create everything on the Earth. 4. Covalent bonds are of practical importance in ... chemistry because of the ability of the carbon atom to form four covalent bonds. 5. ... covalent bonds are common for certain atoms depending upon their valence configuration. 6. An ionic bond can occur at the centre of a large covalently bonded organic molecule such as ... . 7. All bonds arise from the ... of unlike charges. (multiple, combine, attraction, conductivity, enzyme, covalent, organic)