Bonding, Structure And The Properties Of Matter Flashcards
What are the differences between ionic, covalent and metallic bonding?
There are three types of strong chemical bonds: ionic, covalent and metallic. For ionic bonding the particles are oppositely charged ions.
For covalent bonding the particles are atoms which share pairs of electrons. For metallic bonding the particles are atoms which share delocalised electrons.
Ionic bonding occurs in compounds formed from metals combined with non-metals.
Covalent bonding occurs in most non-metallic elements and in compounds of non-metals.
Metallic bonding occurs in metallic elements and alloys.
Explain how an ionic bond is formed?
When a metal atom reacts with a non-metal atom electrons in the outer shell of the metal atom are transferred. Metal atoms lose electrons to become positively charged ions. Non-metal atoms gain electrons to become negatively charged ions. The ions produced by metals in Groups 1 and 2 and by non-metals in Groups 6 and 7 have the electronic structure of a noble gas (Group 0).
The electron transfer during the formation of an ionic compound can be represented by a dot and cross diagram.
What is the structure of an ionic compound?
An ionic compound is a giant structure of ions. Ionic compounds are held together by strong electrostatic forces of attraction between oppositely charged ions. These forces act in all directions in the lattice and this is called ionic bonding.
What is a covalent bond and what are the three types of covalently bonded substances?
When atoms share pairs of electrons, they form covalent bonds. These bonds between atoms are strong.
Covalently bonded substances may consist of small molecules.
Students should be able to recognise common substances that consist of small molecules from their chemical formula.
Some covalently bonded substances have very large molecules, such as polymers.
Some covalently bonded substances have giant covalent structures, such as diamond and silicon dioxide.
What is a metallic bond and how is it structured?
Metals consist of giant structures of atoms arranged in a regular pattern.
The electrons in the outer shell of metal atoms are delocalised and so are free to move through the whole structure. The sharing of delocalised electrons gives rise to strong metallic bonds.
What are the three states of matter and how can they be represented?
The three states of matter are solid, liquid and gas. Melting and freezing take place at the melting point, boiling and condensing take place at the boiling point.
The three states of matter can be represented by a simple model. In this model, particles are represented by small solid spheres.
How can the different freezing/melting and boiling/condensing points of atoms be explained?
The amount of energy needed to change state from solid to liquid and from liquid to gas depends on the strength of the forces between the particles of the substance.
The nature of the particles involved depends on the type of bonding and the structure of the substance.
The stronger the forces between the particles the higher the melting point and boiling point of the substance.
What are the limitations of the particle model?
Limitations of the simple model above include that in the model there are no forces, that all particles are represented as spheres and that the spheres are solid.
What are the four state symbols?
In chemical equations, the three states of matter are shown as (s), (l) and (g), with (aq) for aqueous solutions.
What are the properties of ionic compounds?
Ionic compounds have regular structures (giant ionic lattices) in which there are strong electrostatic forces of attraction in all directions between oppositely charged ions.
These compounds have high melting points and high boiling points because of the large amounts of energy needed to break the many strong bonds.
When melted or dissolved in water, ionic compounds conduct electricity because the ions are free to move and so charge can flow.
What are the properties of small, covalent molecules?
Substances that consist of small molecules are usually gases or liquids that have relatively low melting points and boiling points.
These substances have only weak forces between the molecules (intermolecular forces). It is these intermolecular forces that are overcome, not the covalent bonds, when the substance melts or boils.
The intermolecular forces increase with the size of the molecules, so larger molecules have higher melting and boiling points.
These substances do not conduct electricity because the molecules do not have an overall electric charge.
What are the properties of polymers?
Polymers have very large molecules. The atoms in the polymer molecules are linked to other atoms by strong covalent bonds. The intermolecular forces between polymer molecules are relatively strong and so these substances are solids at room temperature.
What are the properties of polymers?
Polymers have very large molecules. The atoms in the polymer molecules are linked to other atoms by strong covalent bonds. The intermolecular forces between polymer molecules are relatively strong and so these substances are solids at room temperature.
What are the properties of giant covalent structures?
Substances that consist of giant covalent structures are solids with very high melting points. All of the atoms in these structures are linked to other atoms by strong covalent bonds. These bonds must be overcome to melt or boil these substances. Diamond and graphite (forms of carbon) and silicon dioxide (silica) are examples of giant covalent structures.
What are the properties of metals and alloys?
Metals have giant structures of atoms with strong metallic bonding. This means that most metals have high melting and boiling points.
In pure metals, atoms are arranged in layers, which allows metals to be bent and shaped. Pure metals are too soft for many uses and so are mixed with other metals to make alloys which are harder
Why are metals good conductors of electricity and heat?
Metals are good conductors of electricity because the delocalised electrons in the metal carry electrical charge through the metal.
Metals are good conductors of thermal energy because energy is transferred by the delocalised electrons.
Explain the properties of diamond in terms of its structure and bonding?
In diamond, each carbon atom forms four covalent bonds with other carbon atoms in a giant covalent structure, so diamond is very hard, has a very high melting point and does not conduct electricity.
Explain the properties of graphite in terms of its structure and bonding?
In graphite, each carbon atom forms three covalent bonds with three other carbon atoms, forming layers of hexagonal rings which have no covalent bonds between the layers.
In graphite, one electron from each carbon atom is delocalised which makes it similar to metals as it can conduct electricity.
What is graphene and how is it useful?
Graphene is a single layer of graphite and has properties that make it useful in electronics and composites.
What are fullerenes and how are they structured?
Fullerenes are molecules of carbon atoms with hollow shapes. The structure of fullerenes is based on hexagonal rings of carbon atoms but they may also contain rings with five or seven carbon atoms.
The first fullerene to be discovered was Buckminsterfullerene (C60) which has a spherical shape.
What are carbon nanotubes and how are they useful?
Carbon nanotubes are cylindrical fullerenes with very high length to diameter ratios. Their properties make them useful for nanotechnology, electronics and materials.
