Covalent bonding

Question 1

What atoms are involved with covalent bonding?

Answer 1

Non - metal atoms

Question 2

How does covalent bonding occur?

Answer 2

The non metal atoms share their outer electrons do that each atom has a stable noble gas arrangement

Question 3

What is a covalent bond?

Answer 3

A shared pair of electrons

Question 4

What is a molecule?

Answer 4

A molecule is a small group of covalently bonded atoms

Question 5

Why do molecules tend to be neutral?

Answer 5

Molecules tend to be neutral because no electrons have been

Question 6

How is covalent bond represented? Give an example

Answer 6

A covalent bond is represented by a line, Cl - Cl

Question 7

Methane gas is a covalently bonded compound of carbon and hydrogen. Carbon has six electrons and hydrogen has just one electron. How do they covalently bond?

Answer 7

In order for carbon to attain a stable noble gas arrangement, there are four hydrogen atoms to every carbon atom. This produces the formula of methane as CH4

Question 8

What is the formula for methane?

Answer 8

CH4

Question 9

How does sharing electrons hold atoms together?

Answer 9

Atoms with covalent bond are held together by the electrostatic attraction between the nuclei and shared electrons

Question 10

What occurs in double covalent bond?

Answer 10

In a double covalent bond, four electrons are shared within the bond

Question 11

What are the properties of substances with molecular structures?

Answer 11

Substances composed of molecules are gases, liquids or solids with low melting points and are poor conductors of electricity

Question 12

Covalent bonds are very strong but the attraction between them is very weak. Explain this statement

Answer 12

The atoms that have covalently bonded together are strongly bonded together by their covalent bonds within the molecule. However between each molecule there are no strong attachments to each other

Question 13

Why do substances with molecular structures have low melting points?

Answer 13

The strong covalent bonds are only between the atoms within the molecules; there is only a weak attraction holding the molecules together (vann der waals) so the molecules do not need much energy to move apart from each other

Question 14

Why are substances with molecular structures poor conductors of electricity?

Answer 14

The molecules are neutral overall because no electrons are transferred, they are only shared. Therefore there are no charged molecules to carry the current

Question 15

What if a molecule dissolves in water (whilst remaining a molecule), does the solution become a conductor of electricity?

Answer 15

No, if the molecule dissolves in water, but remains as a molecule, the solution does not now conduct electricity. This is because there are no charged particles

Question 16

In some cases, some covalent compounds react with water to form ions. What occurs in this situation?

Answer 16

In cases where covalent compounds react with water to form ions, the resulting solution does conduct electricity

Question 17

What is the term used to describe the situation where one atom provides both electrons in the bond?

Answer 17

Dative covalent bonding or co ordinate bonding

Question 18

What is a dative covalent bond?

Answer 18

A dative covalent bond is a type of covalent bond where one atoms shares both electrons

Question 19

How does dative covalent bonding occur, how are they formed?

Answer 19

In a dative covalent bond, the atom with a lone pair transfer the electrons to an atom that does not have a filled outer main level of electrons. The atom accepts these electrons to become filled

Question 20

The electrons provided by the singular atom in dative covalent bonding are known as what type of electrons?

Answer 20

Lone pair electrons

Question 21

What groups tend to have elements with lone pair electrons?

Answer 21

Lone pairs occur commonly in elements from groups 5,6 and 7

Question 22

In a dative covalent bond, what is the atom that accept the electron pair referred to as?

Answer 22

The atom that accepts the electron pair is an atom that does not hace a filled outer main level of electrons, this atom is described as electron - deficient

Question 23

How are dative covalent bonds represented in diagrams?

Answer 23

Dative covalent bonds are represented by arrows

Question 24

Which direction does the arrow point towards?

Answer 24

The arrow used in the diagram points towards the atom accepting the electron pair only to show how the bond is made

Question 25

What are the four properties of giant covalent structures?

Answer 25

1. They have very high melting and boiling points
2. They can be hard or soft
3. Most are insoluble in water
4. They do not conduct electricity

Question 26

Giant covalent structures have very high boiling and melting points. Why is this?

Answer 26

These compounds have a large number of covalent bonds linking the whole structure so a lot of energy is required to break the lattice

Question 27

Giant covalent structures can be hard or soft. What is an example of a giant covalent structure that is, Hard? Soft?
Why are these giant covalent structures hard? or soft?

Answer 27

Graphite is an example of a soft giant covalent structure. It is soft because the forces between the carbon layer are weak

Diamond and Silicon oxide are examples of hard giant covalent structures. This is because there is difficulty when breaking their 3D networks of strong covalent bonds

Question 28

Almost all metals do not conduct electricity, but some do. What is an example of a metal that does conduct electricity? What is an example of a metal that does not conduct electricity and why?

Answer 28

Graphite is an example of a metal that does conduct electricity. This is because of the delocalised electrons between the carbon layers which can move along the layers when voltage is applied

Diamond and Silicon oxide are examples of metals that do not conduct electricity. This is because all four outer electrons on every carbon atom are involved in a covalent bond so there are no freely moving electrons available