C2.1/2 - Structure and Bonding Flashcards
What is a compound?
Compounds are substances in which atoms of two or more elements are chemically combined.
Why do atoms take part in chemical bonding?
Atoms take part in chemical bonding in order to achieve the electronic structure of a noble gas (full outer energy level).
When an atom loses an electron, what charge does the remaining ion have?
When an atom loses an electron, the remaining ion has a positive charge.
When an atom gains an electron, what charge does the remaining ion have?
When an atom gains an electron, the remaining ion has a negative charge.
What is the electronic structure of an ion?
Ions have the electronic structure of a noble gas (Group 0).
What do we call the elements in Group 1?
The elements in Group 1 are called the Alkali metals.
When Group 1 metals react with non-metal elements, what type of ion is formed?
When Group 1 metals react with non-metal elements, the Group 1 element forms an in with a single positive charge.
What do we call the elements in Group 7?
The elements in Group 7 are called the Halogens.
When Group 7 elements react with the alkali metals, what charge does the halide ion gain?
When Group 7 elements react with alkali metals, the halide ion has a negative charge.
What type of bonding happens when atoms share pairs of electrons?
When atoms share pairs of electrons, this is called covalent bonding.
What do we call covalent molecules with only a small number of atoms, such as H2, Cl2, O2, HCl, H20, NH3 and CH4?
Covalent molecules with only a small number of atoms are called simple molecules.
What are the melting and boiling points of simple molecules and why?
Simple molecules have low melting and boiling points due to the weak intermolecular forces between the molecules.
Why do simple molecules not conduct electricity?
Simple molecules do not conduct electricity as the molecules do not have an overall electric charge.
Why do ionic compounds have high melting and boiling points?
Ionic compounds have high melting and boiling points as there are strong electrostatic forces between oppositely charged ions.
Why do solid ionic compounds not conduct electricity?
Solid ionic compounds cannot conduct electricity because the ions are not free to move.
Why do ionic compounds conduct electricity when they are melted or dissolved in water?
Ionic compounds can conduct electricity when melted or dissolved in water because now the ions are free to move.
What type of molecules are diamond, graphite and silicon dioxide?
Diamond, graphite, and silicon dioxide are giant covalent lattices (macromolecules).
Why do giant covalent structures have very high melting points?
Giant covalent structures have very high melting points as all the atoms are linked to other atoms by strong covalent bonds.
Diamond and graphite are formed from which element?
Diamond and graphite are formed from carbon.
What is the structure of silicon dioxide?
Each silicon atom is covalently bonded to four oxygen atoms.
Each oxygen atom is covalently bonded to two silicon atoms.
What is the structure of diamond?
Each carbon atom forms four covalent bonds.
What is the structure of graphite?
Each carbon atom forms three covalent bonds.
Why is diamond very hard?
Diamond is very hard because each carbon atom forms four strong covalent bonds.
Why is graphite soft and slippery?
Graphite is soft and slippery because it consists of layers.
There are no covalent bonds/weak intermolecular forces between the layers so they are free to slide.
Why is graphite a good conductor of heat and electricity?
In graphite, one electron from each carbon atom is delocalised. The free electrons allow graphite to conduct heat and electricity as they can move and carry energy.
What is the structure of fullerenes?
Fullerenes consist of hexagonal rings of carbon atoms.
What are fullerenes used in?
Fullerenes have uses such as lubricants and in nanotubes.
Why are metals good conductors of heat and electricity?
Metals are good conductors of heat and electricity because they have delocalised electrons that can move.
Why can metals be bent and shaped?
Metals can be bent and shaped because the layers of atoms in metals are able to slide over each other. The atoms are of the same size.
What are alloys?
Alloys are usually made from two or more metals or other elements joined to metals to make them stronger.
Why are alloys harder than pure metals?
Alloys are harder than pure metals because the different sized atoms distort the layers so it is difficult for them to slide over each other.
What are shape memory alloys?
Shape memory alloys can return to their original shape after being deformed, usually by heating (nitinol/dental braces)
What conditions can we change to alter the properties of a polymer?
To alter the properties of a polymer, we can change the temperature of the reaction or use a different catalyst (to produce high-density poly(ethene) or low-density poly(ethene).
What is a thermosoftening polymer?
Thermosoftening polymers consist of individual tanlged polymer chains. When we heat them, these polymers melt and can be reshaped.
What is meant by a thermosetting polymer?
Thermosetting polymersconsist of polymer chains with covalent cross-links between them. They do not melt when they are heated.
In terms of intermolecular forces, why can thermosoftening polymers melt when heated?
Thermosoftening polymers have weak intermolecular forces between the chains. They are easily broken, hence the polymer can melt easily.
What are nanoparticles?
Nanoparticles are between 1-100nm in size. They consist of a few hundred atoms.
Why are nanoparticles useful?
Nanoparticles are useful because they have a high surface area to volume ratio.
