Bonding, Structure, And The Properties Of Matter Flashcards
What are Carbon nanotubes?
- Carbon nanotubes are cylindrical fullerenes with very high length to diameter ratios.
- Their properties make them useful for nanotechnology, electronics and materials.
Who discovered the first fullerene?
The first fullerene to be discovered was Buckminsterfullerene (C60) which has a spherical shape.
What are fullerenes?
- 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.
What is graphene?
Graphene is a single layer of graphite and has properties that make it useful in electronics and composites.
In graphite, what happens to one electron from each carbon atom?
It is delocalised.
What is the carbon 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.
What are the properties of diamond?
- very hard
- very high melting point
- does not conduct electricity
What is the carbon structure of diamond?
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.
Why are metals good thermal conductors?
Metals are good conductors of thermal energy because energy is transferred by the delocalised electrons.
Why are metals good conductors of electricity?
Metals are good conductors of electricity because the delocalised electrons in the metal carry electrical charge through the metal.
What are the properties of pure metals?
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.
What are the properties of metals?
Metals have giant structures of atoms with strong metallic bonding. This means that most metals have high melting and boiling points.
What are examples of giant covalent structures?
Diamond and graphite (forms of carbon) and silicon dioxide (silica) are examples of giant covalent structures.
How are the atoms in giant covalent structures linked?
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.
What is the melting point of giant covalent structures like?
Substances that consist of giant covalent structures are solids with very high melting points.
What are the forces between polymer molecules like?
The intermolecular forces between polymer molecules are relatively strong and so these substances are solids at room temperature.
What are the forces between polymer molecules like?
The intermolecular forces between polymer molecules are relatively strong and so these substances are solids at room temperature.
What are polymers?
Polymers have very large molecules. The atoms in the polymer molecules are linked to other atoms by strong covalent bonds.
Why do small molecules not conduct electricity?
These substances do not conduct electricity because the molecules do not have an overall electric charge.
How does the intermolecular force depend on the size of the molecule?
The intermolecular forces increase with the size of the molecules, so larger molecules have higher melting and boiling points.
What are the forces of small molecules like?
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.
What are the substances that usually consist of small molecules?
Substances that consist of small molecules are usually gases or liquids that have relatively low melting points and boiling points.
What happens when ionic compounds are melted or dissolved in water?
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 substances that usually consist of small molecules?
Substances that consist of small molecules are usually gases or liquids that have relatively low melting points and boiling points.
What happens when ionic compounds are melted or dissolved in water?
When melted or dissolved in water, ionic compounds conduct electricity because the ions are free to move and so charge can flow.
What is the boiling point for ionic compounds like?
- high melting points.
- high boiling points.
- because of the large amounts of energy needed to break the many strong bonds.
What are the structure of ionic compounds like?
lonic compound have regular structures (giant ionic lattices) in which there are strong electrostatic forces of attraction in all directions between oppositely charged ions.
What does aqueous solution stand for as a chemical equation?
(aq)
What are the chemical equations for the three states of matter?
(s), (I) and (g)
What are limitations of the particle theory?
Limitations of the particle theory model include that in the model there are no forces, that all particles are represented as spheres and that the spheres are solid
How does a stronger force affect the melting and boiling point?
The stronger the forces between the particles the higher the melting point and boiling point of the substance.
How do we determine the amount of energy needed to change the state of a substance?
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.
When does melting, freezing, boiling and condensing take place?
Melting and freezing take place at the melting point, boiling and condensing take place at the boiling point.
What are three states of matter?
- solid
- liquid
- gas
In metallic bonding, what do the electrons on the outer shells do?
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 do metals consist of?
Metals consist of giant structures of atoms arranged in a regular pattern.
What are examples of giant covalent structures?
Some covalently bonded substances have giant covalent structures, such as diamond and silicon dioxide.
What do metals consist of?
Metals consist of giant structures of atoms arranged in a regular pattern.
What are examples of giant covalent structures?
Some covalently bonded substances have giant covalent structures, such as diamond and silicon dioxide.
What sort of molecules are in covalently bonded substances?
Some covalently bonded substances have very large molecules, such as polymers.
Do covalently bonded substances consists of just large molecules?
Covalently bonded substances may consist of small molecules.
Are covalent bonds strong or weak?
Covalent bonds between atoms are strong.
What bond is it called when atoms share atoms with pairs of electrons?
Covalent bonds
What is an ionic compound?
An ionic compound is a giant structure of ions. lonic 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 does the charge of ions produced by metals relate to?
The charge on the ions produced by metals in Groups 1 and 2 and by non-metals in Groups 6 and 7 relates to the group number of the element in the periodic table.
What diagram can be used to show an electron transfer during the formation of an ionic compound?
The electron transfer during the formation of an ionic compound can be represented by a dot and cross diagram, eg for sodium chloride.
What structure do ions in group 1,2,6 and 7 produce?
The ions produced by metals in Groups 1 and 2 and by nonmetals in Groups 6 and 7 have the electronic structure of a noble gas (Group 0).
What happens when a metal atom reacts with a non-metal atom?
- Metal atom are transferred.
- Metal atoms lose electrons to become positively charged ions.
- Non-metal atoms gain electrons to become negatively charged ions.
When does metallic bonding occur?
Metallic bonding occurs in metallic elements and alloys.
When does covalent bonding occur?
Covalent bonding occurs in most non-metallic elements and in compounds of non-metals.
When does ionic bonding occur?
lonic bonding occurs in compounds formed from metals combined with non-metals.
What are the atoms like in metallic bonding?
For metallic bonding the particles are atoms which share delocalised electrons.
What are the atoms like for covalent bonding?
For covalent bonding the particles are atoms which share pairs of electrons.
What are ions like for ionic bonding?
For ionic bonding the particles are oppositely charged ions.
What are the three types of strong chemical bonds?
- ionic
- covalent
- metallic
How are ionic compounds held together?
• They are held together in a giant lattice.
• It’s a regular structure that extends in all directions in a substance.
• Electrostatic attraction between positive and negative ions holds the structure together.
State properties of ionic substances
• High melting and boiling point (strong electrostatic forces between oppositely charged ions)
Do not conduct electricity when solid (ions in fixed positions).
• Conduct when moten or dissolved in water- ions are free to move.
Describe the structure and properties of simple molecular covalent substances
- Do not conduct electricity (no ions)
Small molecules - Weak intermolecular forces, therefore:
- Low melting and boiling points
How do intermolecular forces change as the mass/size of the molecule increases?
They increase. That causes melting/boiling points to increase as well (more energy needed to overcome these forces).
What are polymers? What are thermosoftening polymers?
Polymers are very large molecules (>100s, 1000s of atoms) with atoms linked by covalent bonds.
Thermosoftening polymers - special type of polymers; they melt/soften when heated. There are no bonds between polymer chains. Strong intermolecular forces ensure that the structure is solid at room temperature. These forces are overcome with heating - polymer melts.
What are giant covalent substances? Give examples
- Solids, atoms covalently bonded together in a giant lattice.
- High melting/boiling points - strong covalent bonds.
- Mostly don’t conduct electricity (no delocalised e*)
- Diamond, graphite, silicon dioxide.
What are alloys? Why are they harder than pure metals?
Alloys:
- mixtures of metal with other elements, usually metals
- different sizes of atoms distorts the layers, so they can’t slide over each other, therefore alloys are harder than pure metals
What are the limitations of the simple model?
There are no forces between spheres and atoms, molecules and ions are solid spheres - this is not true
What does the amount of energy needed to change state from solid to liquid or liquid to gas depend 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
A pure substance will melt or boil at…? What about the mixture?
A fixed temperature.
A mixture will melt over a range of temperatures.
What is nanoscience?
Science that studies particles that are 1 - 100m in size
State the uses of nanoparticles
- Medicine (drug delivery systems)
- Electronics
- Deodorants
- Sun creams (better skin coverage and more effective protection against cell damage)
What are fine and coarse particles?
- Fine particles (soot), 100-2500 m diameter
- Coarse particles (dust), 2500-105 m diameter
Why do nanoparticles have different properties to those for the same materials in bulk?
High surface area to volume ratio
What are the properties of nanotubes?
Nanotubes
- cylindrical fullerene with high length to diameter ratio
-High tensile strength (strong bonds)
- Conductivity (deloc. electrons)
Graphene - a single layer of graphite.
What are the characteristics of fullerene?
Fullerenes
- hollow shaped molecules
- based on hexagonal rings but may have
5/7-carbon rings
- C6o
• has spherical shape, simple
molecular structure (Buckminsterfullerene)
What are the characteristics of graphite?
Graphite
- three covalent bonds for each carbon atom
- layers of hexagonal rings
- high melting point
- layers free to slide as weak intermolecular forces between layers; soft, can be used as a lubricant
- conduct thermal and electricity due to one delocalised electron per each carbon atom
What are the characteristics of Diamond?
Diamond
-four, strong covalent bonds for each carbon atom
- very hard (Strong bonds)
- very high melting point (strong bonds)
- does not conduct (no delocalised electrons)
What are the three way atoms can combine?
- Ionic bonds
- Covalent bonds
- Metallic bonds
When do ionic bonds take place?
- Takes place when metals and non-metals react by transferring electrons.
- The atoms involved are oppositely charged particles (known as ions) in which electron transfer occurs.
- The opposite charges attract through electrostatic forces.
When do covalent bonds occur?
Non-metal atoms share pairs of electrons between each other.
When do metallic bonds occur?
This type of bonding occurs in metals and metal alloys (mixtures of metals).
What is an ion?
An ion is an electrically charged atom or group of atoms formed by the loss or gain of electrons.
What do the loss or gain of electrons lead to?
A full outer shell of electrons
What is the electronic structure of ions of elements in group 1,2,6 and 7?
It will be the same as the noble gas - such as helium, neon, and argon.
What are negative ions called?
Negative ions are called anions and form when atoms gain electrons, meaning they have more electrons than protons.
What are positive ions called?
Positive ions are called cations and form when atoms lose electrons, meaning they have more protons than electrons.
Why do all metals lose electrons?
All metals lose electrons to other atoms to become positively charged ions.
Why do non-metals gain electrons?
All non-metals gain electrons from other atoms to become negatively charged ions.
How can ionic bonds be shown?
Ionic bonds can be represented diagrammatically using dot and cross diagrams.
What should electrons in the dot and cross diagram show?
- The electrons from each atom should be represented by using solid dots and crosses.
- If there are more than two atoms, then hollow circles or other symbols / colours may be used to make it clear.
What should the large square brackets encompass?
The large square brackets should encompass each atom and the charge should be in superscript and on the right-hand side, outside the brackets.
What happens to the electrons in Sodium (Group 1)?
Sodium is a group 1 metal so loses one outer electron to another atom to gain a full outer shell of electrons.
- A positive sodium ion with the charge 1+ is formed, Na+.
How do you work out the formula of an ionic compound?
- If it is a dot-and-cross diagram, then just count the number of atoms of each element.
- This is then equal to the empirical formula of the compound.
- If it is a 3D lattice structure, then look for how many ions are in the lattice.
- Write them down and balance the charges to find the formula for the compound.
What is the lattice structure made out of?
The lattices formed by ionic compounds consist of a regular arrangement of alternating positive and negative ions in which the ions are tightly packed together.