C2 Flashcards
What is ionic bonding?
The transfer of electrons from a metal to a non-metal
eg. Sodium chloride, Magnesium oxide
What is covalent bonding?
The sharing of electrons between two non-metals
eg. NH3, CH4
What is metallic bonding?
the bonding within a metal/alloy which involves positive ions and a sea of delocalised electrons
- the delocalised electrons (free to move) are able to conduct heat and electricity
Why do electrons become delocalised in metals?
the electron orbitals in metal atoms overlap
Explain ionic bonding
- when a metal atom reacts with a non-metal atom, electrons in the outer shell of the metal atom are transferred
- metal atom loses electrons= positive charged ion (cation), with a full outer shell
- non-metal atom gains electrons= negatively charged ion (anion), with a full outer shell
- the oppositely charged ions are held together by strong electrostatic forces of attraction
What can be used to represent the electron transfer during the formation of an ionic compound?
A dot and cross diagram
What is an ionic compound?
a giant ionic lattice held together by strong electrostatic forces of attraction between oppositely charged ions (which act in all direction in the lattice)
Explain covalent bonding
when atoms share pairs of electrons (for a full outer shell) and form strong covalent bonds
What are limitations of the simple model of the states of matter?
- in the model forces are not shown
- all particles are represented by spheres which is not the case
- the spheres are solid
What are properties of ionic compounds?
- high melting and boiling points due to strong electrostatic forces which requires large amount of energy to overcome
- can conduct electricity when molten or dissolved in water because there are delocalised ions can move and carry a current
Describe the structure and properties of simple covalent bonds(small molecules)
- held together by covalent bonds
- low melting and boiling points because there are weak intermolecular forces that are overcome when the substance melts or boils
- usually gases or liquids
- do not conduct electricity(molecules have no overall electric charge)
Describe the structure and properties of giant covalent structures
- solids with very high melting points
- all atoms in this structure are linked to other atoms by strong covalent bonds
- high amounts of energy are needed to overcome these bonds= high melting and boiling points
eg. diamond, silicon dioxide
What are alloys?
Alloys are made from two or more different types of metals
Why do most metals have high melting and boiling points?
Metals have giant structures of atoms with strong metallic bonding
What are polymers?
Polymers are long chains of repeating units; they are very large molecules that are made up of monomers
What type of bond joins all the atoms in a polymer?
strong covalent bonds
Why are most polymers solid at room temperature?
The intermolecular forces between polymer molecules are relatively strong, so a large amount of energy is needed to break them
What are the two types of polymers?
Addition and Condensation
Describe the structure of diamond
- each atom forms 4 covalent bonds with other carbon atoms
- giant covalent structure so it is very hard has a high melting point
- does not conduct electricity
Describe the structure of graphite
- each carbon atom is covalently bonded to 3 other carbons, forming hexagonal rings(layers). There are no covalent bonds between layers.
- soft(layers can slide) and conducts electricity(due to delocalised electrons)
Give a use of graphite
Pencil
Describe the structure of graphene and fullerenes
- graphene is a single layer of graphite
- uses of graphene: electronics and composites
- fullerenes are molecules of carbon with hollow shapes
- based on hexagonal rings of carbon atoms
- are hard
- can be used as a lubricant, future(drug delivery)
What are nanoparticles?
very small particles of 1-100 nm in size
Give an example of a coarse particle
dust
Why do nanoparticles make good catalysts?
They have high surface area: volume ratios so smaller quantities are needed to be effective than normal size particles
Give uses of nanoparticles
- electronics- small electrical circuits(conduct electricity)
- cosmetics and sun creams
- deodorants
- medicine- drug delivery
Give disadvantages of nanoparticles
- may be toxic
- may be able to enter the blood stream and cause harm
- new so very little scientific knowledge
