C3 Structure and Bonding Flashcards
What is ionic bonding
This is bonding between a metal and a non metal where metals lose electrons and become positively charged and the non metal gains electrons becoming negatively charged. The atoms join by forces of electrostatic attraction and being a compound
What is covalent bonding and how are the atoms drawn to one another
When non-metal atoms bond together, they share pairs of electrons to make covalent bonds. The positively charged nuclei of the atoms are attracted to the shared pair of electrons by electrostatic forces making the bond is very strong
When atoms bond covalently, they gain a full outer shell
What is the group number and the ions they produce
1: 1+
2: 2+
3: 3+
4: 4+ or 4-
5: 3-
6: 2-
7: 1-
0: ❌
What are ionic compounds
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 are drawbacks to using the ionic diagrams
Dot and cross: doesn’t include three dimensional arrangements of the atoms and electron shell or the relative sizes of the atoms
Ball and stick: The atoms are placed far apart from each other, which in reality is not the case as the gaps between atoms are much smaller.
Displayed formula / 2D model: doesn’t show relative sizes of the atoms and bonds
3D model: it doesn’t show the electrons or how the electrons are transfered
Particle model: there are no forces, that all particles are represented as spheres and that the spheres are solid
What do covalently bonded small moleculesmainly constist of
Smaller molecules Cl2, I2, Br2 ( common diatomics )
Give example of giant covalent structures
diamond and silicon dioxide
What do metals consist of
Metals consist of giant structures of atoms arranged in a regular pattern.
How are metals bonded
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 ( electrostatic )
How are ionic compounds structured
Ionic compounds have regular structures (giant ionic lattices) in which there are strong electrostatic forces of attraction in all directions between oppositely charged ions
Why do ionic compounds have high boiling points
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 do ionic compounds conduct electricity
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 molecules
Substances that consist of small molecules are usually gases or liquids that have relatively low melting points and boiling points
These substances do not conduct electricity because the molecules do not have an overall electric charge
Why do small molecules have the properties that they do
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 covalent bonds ( intramolecular forces ) are stronger
Why do larger molecules have high boiling and melting points that smaller molecules
The intermolecular forces increase with the size of the molecules, so larger molecules have higher melting and boiling points
What giant covalent structures and why do they have their properties, give examples
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.
They do not conduct electricity not even when molten because the particles are not charged
Diamond and graphite (forms of carbon) and silicon dioxide (silica) are examples of giant covalent structures
Why do metals have high melting and boiling points
Metals require a lot of energy to break the electrostatic forces of attraction between the ions and sea of delocalised electrons. This means that most metals have high melting and boiling points
Why are metals malleable and ductile and why do alloying them change this
In pure metals, atoms are arranged in layers, they can slide over eachother, which allows metals to be bent and shaped.
Metals are too soft for certain jobs so alloying them makes them harder
The foreign atoms distort the regular arrangement so the metals’ atoms can no longer move over each other easily
Why are metals good conductors
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.
Why is diamond so rigid and non conductive
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 (because it has no free electrons).
What is significant about the structure of graphite
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
What are the properties of graphite
Good lubricant
High melting point
Conducts electricity and thermal energy
What is graphene
Graphene is a sheet of carbon atoms joined in hexagons, it is a 2d substance that can be used in electronics due to it’s properties
What are the properties of graphene
Light ( 1 atom thick )
Strong ( network of covalent bonds )
Conducts electricity ( delocalised electrons )
