1.3 BONDING Flashcards
BONDING
What is ionic bonding?
- Electrostatic attraction between oppositely charged ions in a lattice.
- Ionic bonding occurs between metals and non-metals.
- Metals lose electrons to form positive ions.
- Non-metals gain electrons to form negative ions.
- Electrons are transferred from metals to non-metals.
Ionic bonding is stronger when ions are smaller or have higher charge.
BONDING
What is metallic bonding?
- Electrostatic attraction between delocalised electrons and positive metal ions in a lattice.
- Metallic bonding is stronger when metal ions are smaller or have higher charge
BONDING
What is covalent bonding?
Covalent bonding is a shared pair of electrons. A single covalent bond contains one shared pair of electrons. Multiple bonds contain multiple pairs of electrons.
- A covalent bond is represented using a line
BONDING
What is dative/co-ordinate bonding?
A co-ordinate or dative covalent bond is a shared pair of electrons with both electrons supplied by only one of the bonding atoms.
- a co-ordinate bond is represented using an arrow.
BONDING
Describe an Ionic Structure
A lattice of positive ions each surrounded in a regular arrangement by negative ions and vice versa. Example: sodium chloride.
BONDING
What are the properties of ionic substances?
Ionic compounds have high melting points because of the strong electrostatic attraction between oppositely charged ions, that require a lot of energy to break.
Ionic compounds conduct electricity in the liquid state or when dissolved in water as the ions (charged particles) are free to move through the whole structure.
They do not conduct when they are solid as ions are fixed rigidly in position in the ionic lattice and cannot move.
Ionic compounds are brittle and shatter easily when given a sharp blow. This is because they form a lattice of alternating positive and negative ions. A blow may move the ions and produce contact between ions with like charges, which repel each other and the structure shatters.
BONDING
State and describe the structure, bonding and properties in Sodium Chloride.
Sodium chloride is an ionic compound. It is made of sodium ions which have lost an electron to become positively charged (Na+) and chloride ions which have gained an electron to become negatively charged (Cl-).
Ionic compounds such as sodium chloride are arranged in a giant three-dimensional lattice structure, which is a regular repeating pattern of positive and negative ions. There are strong electrostatic forces of attraction that hold the oppositely charged ions together in the giant lattice. These forces act in all directions of the lattice and form ionic bonds.
It takes a large amount of energy to overcome the strong electrostatic forces of attraction in an ionic compound and therefore they often have high melting and boiling points.
Ionic compounds such as sodium chloride can only conduct electricity when they are melted or dissolved in water. They cannot conduct electricity when they are solid because the ions are not free to move around and carry an electrical charge.
BONDING
Describe the metallic structure
A regular lattice of positively charged metal ions held together by a cloud of delocalised electrons. Example: magnesium
BONDING
What are the properties of metallic substances?
Metals have high melting points because of the strong electrostatic attraction between positively charged metal ions and negatively charged delocalised electrons, that require a lot of energy to break.
Metals conduct electricity as the delocalised electrons (charged particles) are free to move through the whole structure.
Metals are malleable and ductile because they have a regular structure so planes of ions can slide easily over one another. After a small distortion, each metal ion is still in exactly the same environment as before so the structure is retained.
BONDING
Describe the macromolecular structure
Large numbers of atoms are linked in a regular three-dimensional arrangement by covalent bonds. Example: diamond and graphite.
BONDING
What are the properties of diamond and graphite?
Macromolecules have high melting points because of the many strong covalent bonds between the atoms, that require a lot of energy to break.
In diamond each carbon atom forms four strong covalent bonds to four neighbouring carbon atoms, the atoms form a giant three-dimensional lattice, which is why diamond is a hard material. Diamond does not conduct electricity as there are no charged particles that can move through the whole structure.
In graphite each carbon atom forms three strong covalent bonds to three neighbouring carbon atoms. This leaves a ‘spare’ electron from each carbon that is not part of the covalent bonds, which becomes delocalised. Graphite conducts electricity as the delocalised electrons (charged particles) are free to move through the whole layer.
However the van der Waals forces between the layers are much weaker, which means the layers can slide across one another making graphite soft and flaky.
BONDING
Describe the molecular structure
Small molecules (small groups of atoms) strongly held together by covalent bonding but force of attraction between molecules are much weaker.
Molecular crystals consist of molecules held in a regular array by intermolecular forces. Example: ice and iodine.
BONDING
What are the properties of molecular substances?
Simple molecular substances have low melting points because of the weak intermolecular forces (van der Waals, dipole-dipole or hydrogen bonding) between the atoms, that require little energy to break.
Simple molecular substances do not conduct electricity as there are no charged particles that can move through the whole structure.
Simple molecular substances are soft and break easily because of the weak intermolecular forces between the molecules.
BONDING
What is the VESPR (electron pair repulsion) theory
Bonding pairs and lone (non-bonding) pairs of electrons are charged clouds that repel each other.
Pairs of electrons in the outer shell of atoms repel each other to arrange themselves as far apart as possible.
–> Lone pair - lone pair repulsion is greater than lone pair-bond pair repulsion, which is greater than bond pair - bond pair repulsion.
BONDING
Explain Shapes and bond angles of simple molecules and ions
Bond pair - Lone pair - Shape - Angle
Bond pair - Lone pair - Shape - Angle
2 - 0 - linear - 180°
3 - 0 - trigonal planar - 120°
2 - 1 - V-shaped - 117.5°
4 - 0 - tetrahedral - 109.5°
3 - 1 - trigonal pyramidal - 107°
2 - 2 - V-shaped - 104.5°
5 - 0 - trigonal bipyramidal - 120° and 90°
4 - 1 - seesaw - 117.5° and 87.5°
3 - 2 - T-shaped - 87.5°
6 - 0 - octahedral - 90°
5 - 1 - square pyramidal - 87.5°
4 - 2 - square planar - 90°
