- formation of ionic bonds between metallic and non-metallic elements
Metallic bonding
Metals form giant structures in which electrons in the outer shells of the metal atoms are free to move. The metallic bond is the force of attraction between these free electrons and metal ions. Metallic bonds are strong, so metals can maintain a regular structure and usually have high melting and boiling points.
Metals form giant structures in which electrons in the outer shells of the metal atoms are free to move. The metallic bond is the force of attraction between these free electrons and metal ions. Metallic bonds are strong, so metals can maintain a regular structure and usually have high melting and boiling points.
Properties of metals:
1. Metals have high melting points
This is because it takes a lot of heat energy to break up the lattice.
2. Metals are malleable and ductile.
Malleable: They can be bent and pressed into shapes. Ductile: They can be drawn out into wires.
This is because the layers can slide without the metallic bond breaking, because the electrons are free to move too.
3. Metals are good conductors of heat
That’s because the free electrons take in heat energy, which makes them move faster and they quickly transfer the heat through the metal structure.
4. Metals are good conductors of electricity
This is because the free electrons can move through the lattice carrying the charge.
1. Metals have high melting points
This is because it takes a lot of heat energy to break up the lattice.
2. Metals are malleable and ductile.
Malleable: They can be bent and pressed into shapes. Ductile: They can be drawn out into wires.
This is because the layers can slide without the metallic bond breaking, because the electrons are free to move too.
3. Metals are good conductors of heat
That’s because the free electrons take in heat energy, which makes them move faster and they quickly transfer the heat through the metal structure.
4. Metals are good conductors of electricity
This is because the free electrons can move through the lattice carrying the charge.
- the lattice structure of ionic compounds as a regular arrangement of alternating positive and negative ions
Groups
- The group number tells you how many electrons there are in the outer shell of the atoms.
- The outer-shell electrons are also called valency electrons and their number shows how the elements behave.
- All elements in a group have similar properties.
- Group 0 elements have a full outer shell. This makes them unreactive.
- Some of the groups have special names:
Group 1 – The alkali metals
Group 2 – The alkaline earth metals Group 7 – The halogens
Group 0 – The noble gases
Periods
The period number gives information about the number of electron shells that are available in that period.
Hydrogen
Hydrogen sits alone in the table because it’s the only element with one electron shell.
The period number gives information about the number of electron shells that are available in that period.
Hydrogen
Hydrogen sits alone in the table because it’s the only element with one electron shell.
Trends in the periodic table
The elements in each numbered group shows trends in their properties. For example as you go down group 1, the elements become more reactive or as you go down group 7 the elements become less reactive and so on.
The elements in each numbered group shows trends in their properties. For example as you go down group 1, the elements become more reactive or as you go down group 7 the elements become less reactive and so on.
Group 1: The alkali metals
Their physical properties:
- Like all metals, they are good conductors of heat and electricity.
- They are softer than most other metals and they have low density.
- They have low melting and boiling points, compared to most metals.
- All alkali metals react vigorously with water, releasing hydrogen gas and forming hydroxides. The hydroxides give alkaline solutions.
- They react with non-metals. With chlorine they react to make chlorides and with oxygen they make oxides.
Why they have similar properties?
Because atoms with the same number of valency electrons react in a similar way.
As you go down the group reactivity increase.
Why?
Because the atoms get larger down the group because they add electron shells.
Because atoms with the same number of valency electrons react in a similar way.
As you go down the group reactivity increase.
Why?
Because the atoms get larger down the group because they add electron shells.
Group 7: The halogens
A non-metal group.
- Form colored gases.
- Are poisonous
- Are brittle and crumbly in their solid form, and do not conduct electricity.
- Form diatomic molecules (means they exist as 2 atoms)
Trends in their chemical properties
Reactivity increases as you go up group 7.
Because the smaller the atom, the easier it is to attract the electron – so the more reactive the element will be.
Why are they so reactive?
Because their atoms are only one electron short of a full shell.
Reactivity increases as you go up group 7.
Because the smaller the atom, the easier it is to attract the electron – so the more reactive the element will be.
Why are they so reactive?
Because their atoms are only one electron short of a full shell.
Group 0: The noble gases
A non-metal group
- Contains colorless gases, which occur naturally in air
- Monatomic – they exist as single atoms
- Unreactive because they have a full outer shell.
The transition elements
The transition elements are the block of 30 elements in the middle of the periodic table. They are all metals.
Their physical properties
Their physical properties
- Hard, tough and strong
- High melting points (mercury is an exception)
- Malleable and ductile
- Good conductors of heat and electricity
- High density
Their chemical properties
- They are much less reactive than the metals of group 1.
- They show no clear trend in reactivity, unlike the metals of group 1.
- Most transition metals form colored compounds
- Most can form ions with different charges (they have variable valency)
- They can form more than one compound with another element
- Most transition metals can form complex ions
- The hard strong transition metals are used in structure such as bridges, buildings, cars etc.
- Many transition metals are used in making alloys.
- Transition metals are used as conductors of heat and electricity.
- Many transition metals and their compounds act as catalysts
Silicon (IV) oxide
There are three different crystal forms of silicon dioxide. The easiest one to remember and draw is based on the diamond structure. Crystalline silicon has the same structure as diamond. To turn it into silicon dioxide, all you need to do is to modify the silicon structure by including some oxygen atoms.
Notice that each silicon atom is bridged to its neighbours by an oxygen atom. Don't forget that this is just a tiny part of a giant structure extending on all 3 dimensions.
The physical properties of Silicon (IV) Oxide:
There are three different crystal forms of silicon dioxide. The easiest one to remember and draw is based on the diamond structure. Crystalline silicon has the same structure as diamond. To turn it into silicon dioxide, all you need to do is to modify the silicon structure by including some oxygen atoms.
Notice that each silicon atom is bridged to its neighbours by an oxygen atom. Don't forget that this is just a tiny part of a giant structure extending on all 3 dimensions.
The physical properties of Silicon (IV) Oxide:
- It has a high melting point - varying depending on what the particular structure is (remember that the structure given is only one of three possible structures), but around 1700°C. Very strong silicon-oxygen covalent bonds have to be broken throughout the structure before melting occurs.
- It is hard. This is due to the need to break the very strong covalent bonds.
- It doesn't conduct electricity. There aren't any delocalised electrons. All the electrons are held tightly between the atoms, and aren't free to move.
- It is insoluble in water and organic solvents. There are no possible attractions which could occur between solvent molecules and the silicon or oxygen atoms which could overcome the covalent bonds in the giant structure.