STRUCTURE OF METAL

Arrangement of atoms in metals forms a closely packed regular giant structure.

· " Giant" implies that large but variable numbers of atoms are involved - depending on the size of the bit of metal.

· In metals, the atoms are ionized, loosing some electrons from the outer most shell.

· The electrostatic attraction between the positive metal ions and the negative delocalized electrons binds the ions together.

·

The delocalized electrons between the atoms enable metals to conduct heat and electricity, and give the metal malleability, as the atoms can slide over each other.

· Delocalized electrons means that they do not move in a fixed position.

· The electrons move freely in the empty space between the positive metal ions.

· Metals have high melting points, which suggests that there are strong chemical bonds between the atoms.

SIMPLE MOLECULAR SUBSTANCES

· The molecules of non-metals are often made up of two identical atoms covalently bonded together, for example: oxygen (O₂), hydrogen (H₂), and nitrogen (N₂). There are also molecular compounds made up of different non-metal atoms bonded together, such as water (H₂O), ammonia (NH₃), and carbon dioxide (CO₂)

· Simple molecular structures have distinctive properties. Although the covalent bonds within the molecules are very strong, the weak intermolecular forces are easily broken.

· As the molecules can be parted easily, simple molecular substances are not very hard or strong and have low melting and boiling points. At room temperature, most simple molecular substances are either a gas or liquid. They do not usually dissolve in water and do not conduct electricity because they have no ions.

There are two kinds of intermolecular forces,

· Van der Waals forces:

- Exist between simple covalent molecules

· Hydrogen bonding:

- Occurs in polar molecules containing hydrogen

- Stronger than Van der Waals’ forces but is still much weaker than covalent bond because it’s just an attraction.

IONIC COMPOUND STRUCTURE

· Ionic compounds consist of positive metallic ions and negative-metallic ions bonded together by electrostatic forces of attraction.

· They mostly form a giant crystal lattice pattern,this results in the compound forming crystals with definite shapes.

· These crystal lattice structures are very stable because of the strong ionic bonds

· between the two oppositely charged ions.

· These require large amount of energy to overcome.

An example is: Sodium Chloride

· Most ionic compounds are solids with hight melting and boiling point.

· They are also a non-conductor of electricity in solid state, but a conductor in

· molten or aqueous state.

· Chemical compounds are never strictly ionic. Even the most electronegative/electropositive pairs such as caesium fluoride exhibit a degree of covalency. Similarly, covalent compounds often exhibit charge separations. See also HASB theory.

MACROMOLECULAR STRUCTURE

· In a macromolecular structure, all the atoms in

· the crystal are held together by strong covalent

· bonds to give a giant three-dimensional lattice.

· This is the reason why it is so stable.

An example of such is diamond.

(tetrahedral structure)

· The carbon atoms are all bonded together by very strong covalent bonds to give a giant three-dimensional network.

· This results in a network of covalent bonds.

· Due to the large amount of energy required to overcome these bonds, the diamond is rigid and strong, and has a high melting point. They do not conduct electricity at all, and are generally insoluble in all solvents.

The term macromolecule was coined by Nobel Laureate Hermann Staudinger in the 1920s although his first relevant publication on this field only mentions high molecular compounds (in excess of 1000 atoms). At that time the phrase polymer as introduced by Berzelius in 1833 had a different meaning from that of today: it simply was another form of isomerism for example with benzene and acetylene and had little to do with size.

Personal thoughts:

I honestly think that this topic isn't that very much interesting. This could because I have only learnt the basics of this topic. (Although the macromolecular one does seem interesting : D) Descriptions of the compound were pretty simple, whilst the macromolecular one was more complex, it showed how the (in a diamond) different carbon atoms are linked together by strong covalent bonds, this then goes on to show how it eventually ends up as a giant crystal lattice structure. The info from the internet about the structure of metals and simple molecular substances is explained in detail which is easy to understand and grasp the concept about howI hope through this project, it will help other students to understand more about these two. Credits to Cheryl Seah.

STRUCTURE OF METAL

Arrangement of atoms in metals forms a closely packed regular giant structure.

· " Giant" implies that large but variable numbers of atoms are involved - depending on the size of the bit of metal.

· In metals, the atoms are ionized, loosing some electrons from the outer most shell.

· The electrostatic attraction between the positive metal ions and the negative delocalized electrons binds the ions together.

·

The delocalized electrons between the atoms enable metals to conduct heat and electricity, and give the metal malleability, as the atoms can slide over each other.

· Delocalized electrons means that they do not move in a fixed position.

· The electrons move freely in the empty space between the positive metal ions.

· Metals have high melting points, which suggests that there are strong chemical bonds between the atoms.

SIMPLE MOLECULAR SUBSTANCES

· The molecules of non-metals are often made up of two identical atoms covalently bonded together, for example: oxygen (O₂), hydrogen (H₂), and nitrogen (N₂). There are also molecular compounds made up of different non-metal atoms bonded together, such as water (H₂O), ammonia (NH₃), and carbon dioxide (CO₂)

· Simple molecular structures have distinctive properties. Although the covalent bonds within the molecules are very strong, the weak intermolecular forces are easily broken.

· As the molecules can be parted easily, simple molecular substances are not very hard or strong and have low melting and boiling points. At room temperature, most simple molecular substances are either a gas or liquid. They do not usually dissolve in water and do not conduct electricity because they have no ions.

There are two kinds of intermolecular forces,

· Van der Waals forces:

- Exist between simple covalent molecules

· Hydrogen bonding:

- Occurs in polar molecules containing hydrogen

- Stronger than Van der Waals’ forces but is still much weaker than covalent bond because it’s just an attraction.

IONIC COMPOUND STRUCTURE

· Ionic compounds consist of positive metallic ions and negative-metallic ions bonded together by electrostatic forces of attraction.

· They mostly form a giant crystal lattice pattern,this results in the compound forming crystals with definite shapes.

· These crystal lattice structures are very stable because of the strong ionic bonds

· between the two oppositely charged ions.

· These require large amount of energy to overcome.

An example is: Sodium Chloride

· Most ionic compounds are solids with hight melting and boiling point.

· They are also a non-conductor of electricity in solid state, but a conductor in

· molten or aqueous state.

· Chemical compounds are never strictly ionic. Even the most electronegative/electropositive pairs such as caesium fluoride exhibit a degree of covalency. Similarly, covalent compounds often exhibit charge separations. See also HASB theory.

MACROMOLECULAR STRUCTURE

· In a macromolecular structure, all the atoms in

· the crystal are held together by strong covalent

· bonds to give a giant three-dimensional lattice.

· This is the reason why it is so stable.

An example of such is diamond.

(tetrahedral structure)

· The carbon atoms are all bonded together by very strong covalent bonds to give a giant three-dimensional network.

· This results in a network of covalent bonds.

· Due to the large amount of energy required to overcome these bonds, the diamond is rigid and strong, and has a high melting point. They do not conduct electricity at all, and are generally insoluble in all solvents.

The term macromolecule was coined by Nobel Laureate Hermann Staudinger in the 1920s although his first relevant publication on this field only mentions high molecular compounds (in excess of 1000 atoms). At that time the phrase polymer as introduced by Berzelius in 1833 had a different meaning from that of today: it simply was another form of isomerism for example with benzene and acetylene and had little to do with size.

Personal thoughts:

I honestly think that this topic isn't that very much interesting. This could because I have only learnt the basics of this topic. (Although the macromolecular one does seem interesting : D) Descriptions of the compound were pretty simple, whilst the macromolecular one was more complex, it showed how the (in a diamond) different carbon atoms are linked together by strong covalent bonds, this then goes on to show how it eventually ends up as a giant crystal lattice structure. The info from the internet about the structure of metals and simple molecular substances is explained in detail which is easy to understand and grasp the concept about howI hope through this project, it will help other students to understand more about these two. Credits to Cheryl Seah.