C2 - Bonding, Structure, & Properties Of Matter Flashcards
What is an ion?
- Cation
- Anion
An atom that has gained or lost electrons.
Electrons are negative;
Cation - It has lost electrons so it will be positively charged.
Anion - It has gained electrons so it will be negatively charged.
What is ionic bonding?
Bonding between oppositely charged particles, held together by electrostatic forces of attraction.
The positive ions are often metals and the negative ions are often non-metals.
Describe how an ionic bond forms between a metal atom and a non-metal atom, in terms of electron transfer.
The metal atom loses electrons to form a positively charged ion.
The non-metal atom gains these electrons to form a negatively charged ion.
These oppositely charged ions form an ionic bond, due to the electrostatic forces of attraction between them.
Explain why ionic compounds conduct electricity when molten, but not when solid.
The ions in a solid ionic compound are held in place in a giant lattice structure, so they cannot move around.
When an ionic compound melts, the ionic bonds break and the ions become free to move and can carry an electric charge.
Do ionic compounds have high or low melting points? Why?
Ionic compounds have high melting points, because of the strong electrostatic forces of attraction between the ions.
What is the structure of ionic compounds?
A regular lattice structure which is closely packed and held together by strong electrostatic forces of attraction in all directions.
What is covalent bonding?
Bonding between 2 non-metals, that share a pair of electrons.
What are the 2 forms of covalent bonding structures?
. Simple molecular
. Giant lattice - (such as polymers and giant covalent structures)
What are simple molecules?
A structure containing a few distinct groups of atoms, which are held together by covalent bonds.
What are some common examples of simple molecular substances?
Hydrogen
Oxygen
Methane
Chlorine
Nitrogen
Water
Hydrogen chloride
Describe the properties of simple molecular substances?
Very strong covalent bonds between atoms
Very weak forces of attraction between molecules = very low melting & boiling points because molecules are easily parted from each other
Don’t conduct electricity because there aren’t charged so there are no free electrons or ions
As molecules get bigger, the strength of intermolecular forces increases and more energy needed to break them
What is a polymer?
Lots of small units linked together to form a long molecule that has repeating sections.
Describe the structure and properties of polymers
Lots of small unfits linked together by strong covalent bonds to form a long molecule.
The intermolecular forces are larger than in simple molecules so most polymers are solid at room temperature.
Weaker intermolecular forces than ionic or giant molecular compounds so they have lower melting and boiling points.
What is a giant covalent structure?
What are the main examples of giant covalent structures?
A macromolecule (a molecule containing a very large number of atoms) where all the atoms are bonded to each other by strong covalent bonds
Diamond, graphite, and silicone dioxide.
Describe the properties of giant covalent structures
Very high melting and boiling points because a lot energy is needed to break the covalent bonds between atoms
Don’t conduct electricity because there are no charged particles
What is an allotrope?
What are some allotropes of carbon?
Allotropes are different structural forms of the same element in the same physical state.
Diamond, graphite, and fullerenes.
Describe the structure and properties of Diamond
Diamond has a giant covalent structure, made up of carbon atoms that each from four covalent bonds. This makes diamond really hard.
The strong covalent bonds take a lot of energy to break and give diamond a very high melting point.
Diamond doesn’t conduct electricity because there are no free electrons or ions.
Describe the structure of Graphene
- each carbon atom forms three covalent bonds arranged in hexagons
- conducts electricity & thermal energy - three out of four electrons in each carbon’s outer shell are used in bonds so one electron is delocalised and free to move
- high melting point - strong covalent bonds need lots of energy to break
- no covalent bonds between the layers - they’re held together weakly, so they can slide over each other. this means graphite is soft and slippery, so it’s ideal as a lubricating material.
Describe the structure, properties, & uses of Fullerenes
- Made up of carbon atoms mainly arranged in hexagons or sometimes pentagons/heptagons.
- Shaped like closed tubes or hollow balls.
- Fullerenes form around another atom or molecule - can ‘cage’ a molecule and used to deliver drugs into the body
- Large surface area - make great industrial catalysts and used as lubricants
Fullerenes can form nanotubes:
- conduct electricity and thermal energy
- high tensile strength (don’t break when stretched)
- used in electronics (nanotechnology) or to strengthen materials without adding much weight
(e.g. in tennis racket frames)
What is metallic bonding? And what does it consist of?
Bonding between metallic elements and alloys.
Consists of giant structures of atoms arranged in a regular pattern.
Why are most metals solid at room temperature?
There are very strong electrostatic forces between the metal atoms and the delocalised sea of electrons, so lots of energy needed to be broken.
This means that most compounds with metallic bonds have very high melting and boiling points, so they’re generally solid at room temperature.
Why are metals good conductors of electricity?
The delocalised electrons carry electrical charge and thermal energy through the whole structure, so metals are good conductors of electricity and heat.
Why are most metals malleable?
The layers of atoms in a metal can slide over each other, making metals malleable - this means that they can be bent or hammered or rolled into flat sheet.
What is an alloy?
Why are alloys harder than pure metals?
Alloy - a mixture of a metal and another metal or element
When pure metal is mixed with another element, the new atoms are different sizes from the metal atoms. This distorts the layers of metal atoms, making it difficult for them to slide over each other. So they are harder than pure metals.
