Covalent bonding Flashcards
What atoms are involved with covalent bonding?
Non - metal atoms
How does covalent bonding occur?
The non metal atoms share their outer electrons so that each atom has a stable noble gas arrangement
What is a covalent bond?
A covalent bond is a shared pair of electrons between two non - metal atoms
What is a molecule?
A molecule is a small group of covalently bonded atoms
Why do molecules tend to be neutral?
Molecules tend to be neutral because when molecules form they do not transfer electrons, they just share electrons
How is covalent bond represented? Give an example
A covalent bond is represented by a line, Cl - Cl
What occurs in double covalent bond?
In a double covalent bond, four electrons are shared within the bond
What are the properties of substances with molecular structures?
Substances composed of molecules are gases, liquids or solids with low melting points and are poor conductors of electricity
Covalent bonds are very strong but the attraction between them is very weak. Explain this statement
The atoms within the molecule that are bonded together have storng covalent bonds. However between each molecule there are no strong attachments to each other, mkaing the attraction between them very weak
Why do substances with molecular structures have low melting points?
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
Why are substances with molecular structures poor conductors of electricity?
Molecular structures are poor conductors of electricity because molecules are overall neutral because electrons are not transferred, they are only shared. As a result, there are no charged molecules to carry the current
What if a molecule dissolves in water (whilst remaining a molecule), does the solution become a conductor of electricity?
No, this is because there are still no charged particles to carry the current in the water
In some cases, some covalent compounds react with water to form ions. What occurs in this situation, involving their ability to conduct electricity?
In cases where covalent compounds react with water to form ions, the resulting solution does conduct electricity
What is the term used to describe the situation where one atom provides both electrons in the bond?
Dative covalent bonding or co ordinate bonding
What is a dative covalent bond?
A dative covalent bond is a type of covalent bond where one atoms shares both electrons
How does dative covalent bonding occur, how are they formed?
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
The electrons provided by the singular atom in dative covalent bonding are known as what type of electrons?
Lone pair electrons
What groups tend to have elements with lone pair electrons?
Lone pairs occur commonly in elements from groups 5,6 and 7
In a dative covalent bond, what is the atom that accept the electron pair referred to as?
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
How are dative covalent bonds represented in diagrams?
Dative covalent bonds are represented by arrows
Which direction does the arrow that shows dative covalent bonding point towards?
The arrow used in dative covalent bonding points towards the atom accepting the electron pair only to show how the bond is made
What are the four properties of giant covalent structures?
- They have very high melting and boiling points
- They can be hard or soft
- Most are insoluble in water
- They do not conduct electricity
Giant covalent structures have very high boiling and melting points. Why is this?
These compounds have a large number of covalent bonds linking the whole structure so a lot of energy is required to break the lattice
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?
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
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?
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
