Save My Exams bonding Flashcards
Changes of state
physical changes that are reversible
do not change the chemical properties or chemical makeup of the substances involved
Evaporation
he change of liquid to gas, but unlike boiling, evaporation occurs only at the surface and takes place at temperatures below the boiling point
Boiling
occurs at a specific temperature and takes place when the vapour pressure reaches the external atmospheric pressure
Between 1 & 2 on change of state graph
the particles are vibrating and gaining kinetic energy and the temperature rises
Between 2 & 3
all the energy goes into breaking bonds – there is no increase in kinetic energy or temperature
Between 3 & 4
particles are moving around and gaining in kinetic energy
Between 4 & 5
the substance is boiling, so bonds are breaking and there is no increase in kinetic energy or temperature
5 & 6
particles are moving around rapidly and increasing in kinetic energy
Ionic bonding
the transfer of electrons from a metallic element to a non-metallic element
Transferring electrons usually leaves the metal and the non-metal with a full outer shell
formed between the oppositely charged ions, which occurs in all directions
Electrostatic attractions
formed between the oppositely charged ions to form ionic compounds
ions form a
lattice structure which is an evenly distributed crystalline structure
regular repeating pattern so that positive charges cancel out negative charges
Each ion is attracted to all of the oppositely charged ions around it
Therefore the final lattice is overall electrically neutral
Covalent bonding
occurs between two non-metals
A covalent bond involves the electrostatic attraction between nuclei of two atoms and the bonding electrons of their outer shells
No electrons are transferred but only shared
how many electrons shared in single carbon bond
2
how many electrons shared in double carbon bonds
4
how many electrons shared triple carbon bonds
6
expanding the octet rule’
Being able to accommodate more than 8 electrons in the outer shell
electron deficient’
Accommodating less than 8 electrons in the outer shell means than the central atom is ‘electron deficient’
Dative Covalent Bonding
Some molecules have a lone pair of electrons that can be donated to form a bond with an electron-deficient atom
An electron-deficient atom is an atom that has an unfilled outer orbital
So both electrons are from the same atom
This type of bonding is called dative covalent bonding or coordinate bonding
In a dot and cross diagram:
Only the outer electrons are shown
The charge of the ion is spread evenly which is shown by using brackets
The charge on each ion is written at the top right-hand corner
Ionic compounds
Ionic bonds are formed when metal atoms transfer electrons to a non-metal to form a positively charged and negatively charged ion
The atoms achieve a noble gas configuration
Covalent compounds
The atoms in covalent compounds will share their outer valence electrons to achieve a noble gas configuration
Metallic Bonding
tightly packed together in lattice structures
electrons in their outer shells are free to move throughout the structure
‘delocalised electrons’
When the electrons are delocalised, the metal atoms become positively charged ions
The positive charges repel each other and keep the neatly arranged lattice in place
There are very strong forces between the positive metal centres and the ‘sea’ of delocalised electrons
Giant ionic lattices
When an ionic compound is formed, the attraction between the ions happens in all directions
Ionic compounds are arranged in giant ionic lattices (also called giant ionic structures)
The type of lattice formed depends on the sizes of the positive and negative ions which are arranged in an alternating fashion
The ionic lattice of MgO and NaCl are cubic
Covalent lattices
Covalent compounds can be arranged in simple molecular or giant molecular lattices
Simple molecular lattices: iodine, buckminsterfullerene (C60) and ice
Giant molecular: silicon(IV) oxide, graphite and diamond
Graphite, diamond and buckminsterfullerene are all
allotropes of carbon; they are different structural forms of the same element (which is carbon).
giant metallic lattice
metal ions are surrounded by a ‘sea’ of delocalised electrons
packed in hexagonal layers or in a cubic arrangement
alloy
If other atoms are added to the metal structure, such as carbon atoms, this creates an alloy
Alloys are much stronger than pure metals, because the other atoms stop the layers of metal ions sliding over each other easily
strength of the metallic attraction can be increased by:
Increasing the number of delocalised electrons per metal atom
Increasing the positive charges on the metal centres in the lattice
Decreasing the size of the metal ions
properties of metallic compounds
1)HIGH M+B
2)good conductors
3)malleable and ductile
high m+b metallic
strong metallic bonds
large amounts of heat energy needed to over come and break bonds
good conductors metallic
free electrons
move and carry charge
maleable and ductile metallic
layers of positive ions sliding over each other
Simple covalent lattices have low melting and boiling points
These compounds have weak intermolecular forces between the molecules
Only little energy is required to break the lattice
Most compounds are insoluble with water
They do not conduct electricity in the solid or liquid state as there are no charged particles
Giant covalent lattices have very high melting and boiling points
These compounds have a large number of covalent bonds linking the whole structure
A lot of energy is required to break the lattice
Graphite is soft
the forces between the carbon layers are weak
Diamond and silicon(IV) oxide are hard as it is difficult to break their 3D network of strong covalent bonds
Metallic structures are malleable
When a force is applied, the metal layers can slide
The attractive forces between the metal ions and electrons act in all directions
So when the layers slide, the metallic bonds are re-formed
The lattice is not broken and has changed shape
