Chemistry Topic 2

Ionic Bonding

Ionic bonding is the process of an atom donating electrons to another atom, since electrons have a tendency to stabilise after having a full outer shell of electrons (Octet Rule)

Example: 

Lithium: 2,1

Fluorine: 2,7

Both the lithium and the fluorine can be stabilised if they form an ionic bond. The lithium can donate its single electron to fluorine so they can both have an outer shell. 

Note: Clean 100% Ionic bonding does not exist, as all ionic compounds have a degree covalent bonding or electron sharing.

  • Explain how and why ions are formed.

Ions are formed by simply giving or taking electrons from the atom. 

Ions are formed so they can achieve a more stable configuration. An atom is the most stable when it has a full outer shell (Octet Rule).


  • Explain the difference between cations and anions

Both refer to the charge of an ion

Cation: A positive ion, where they lose electrons, (can be remembered as cat, good)

Anions: A negative ion, when they gain electrons

  • Understand the octet rule and how it applies to the formation of monatomic ions

Monatomic Ions: Charged particles formed from a single atom that has either gained or lost electrons making it a Cation or Anion

Octet Rule: The octet rule refers to the tendency of atoms to prefer having 8 electrons in their outer shell.

  • Draw electron-dot diagrams to show the transfer of electrons between metal and non-metal atoms

For reference, lewis dot, electron dot, and dot and cross diagrams are pretty much the same thing

For the example Sodium and Chlorine, with sodium being a metal and chlorine being the non-metal. The first step is to find the chemical symbol, alongside the amount of valence electrons both the atoms have. The number of valence electrons are to be drawn around the chemical symbol.

The next step is to show the ionic bond, keeping in mind the octet rule, and the fact that an atom is most stable when it has a full valence shell. The last step is to show the charge of the individual atoms by closing them with square brackets and the charge outside.


  • Assign a chemical formula and name for an ionic compound (including monatomic, transition metal and polyatomic ions) 

Monatomic: 

Chemical Formula: For ionic compounds, they consist of a metal and a non-metal. To assign a chemical formula, the ionic charge and symbol need to be found alongside the quantity for both atoms present in the ionic bond to make it stable.

Chemical Name: The cation (positive ion) is said first alongside the anion. The anion then contains the suffix -ide.

Keep in mind that prefixes for the anion, such as mono- is only included for covalent compounds.

Transition Metals: 

Chemical Formula: Compared to metals, transition metals can have different oxidation states, which can make them have different charges. For example, Fe (I) has a 1+ charge, while Fe (II) has a 2+ charge. 

Chemical Name: With transition metals, since some of them have different ions such as Fe (I) and Fe (II), the type should be written in brackets. For example, Iron (II) oxide and Iron (III) oxide.

Polyatomic: 

Chemical Formula: Write the element symbol for the metal and its charge (the cation)

Find the name and charge of the polyatomic ion

Balance the charges by adding subscripts

Chemical name: Don't gotta know

  • Describe the bonding and structure of an ionic compound 

An ionic compound is formed when one atom gives electrons to another atom. The structure of an ionic compound is a lattice structure, which consists of a cube with each square face consisting of an alternating pattern between the two elements.

  • Explain the physical properties of an ionic compound using the model of an ionic compound, including:

    • brittle

Ionic compounds are generally brittle because of the arrangement of ions in a crystal lattice structure. When force is applied, layers of ions shift; if like-charged ions align, they repel each other, causing the crystal to shatter. This is in contrast to metals, which can deform without breaking.

  • crystal lattice structure 

Ionic compounds form a crystal lattice, a three-dimensional arrangement of ions held together by strong electrostatic forces (ionic bonds). This common arrangement maximises attraction between oppositely charged ions while minimising repulsion among like-charged ions. The lattice structure contributes to the stability and hardness of ionic compounds.

  • poor conductors of electricity in solid state

In solid form, ionic compounds (lattice structure), do not conduct electricity well because the ions are very tightly fixed in place and cannot move freely. Electrical conductivity requires the movement of charged particles, which is not possible in the solid state. 

  • good conductors of electricity in molten (liquid) or aqueous state

When ionic compounds are melted down or dissolved in water, the crystal lattice breaks down, allowing the ions to move freely. In this state, the mobile ions can carry an electric current.

  • high melting point

Ionic compounds typically have high melting points due to the strong electrostatic forces of attraction between between the oppositely charged ions in the crystal lattice. Therefore, a significant amount of energy is required to overcome these forces and seperate these ions, which means higher temperatures are required for it to melt and break apart. 

Metallic Bonding

  • Know that the chemical formula of a metallic element is simply its chemical symbol

Self explanatory, examples:

Iron (Fe): Symbol is Fe

Copper (Cu): Symbol is Cu

Gold (Au): Symbol is Au

All metallic elements are single elements, and no subscripts are needed.

  • Describe the bonding and structure of a metallic substance 

Metallic bonding only consists of metals. They consist of positive cations, surrounded by a “sea of delocalised electrons”.

Sea of delocalised electrons: In a metallic bond, the metals lose their valence electrons which turns them into cations. A sea of delocalised electrons then form because the excess electrons do not belong to a single element, and instead, are free to move throughout the metallic structure. 

For example:

The metal iron (Fe) can metallically bond with itself. Since iron has 2 valence electrons, every single iron element in the bond loses the 2 valence electrons to contribute to the sea of delocalised electrons.

  • Explain the physical properties of a metallic substance using the model of a metallic substance, including:

    • lustrous (shiny)

Metallic substances are shiny due to the sea of delocalised electrons. When light strikes the surface of the metal, the free electrons absorb and re-emit the light energy. This is because when the light energy hits the delocalised electrons, the energy is transferred to the electrons. Which makes the electrons excited. This state is temporary and they will eventually return to their normal state. As the electrons return to their ground state, they release the absorbed light energy.

  • good conductors of electricity in solid and liquid state

Metals are excellent conductors of electricity because of the sea of delocalised electrons. In both the solid and liquid states, the electrons move freely, which means when they come in contact with electricity, the electrons carry the charge efficiently. 

  • good conductors of heat

Metals conduct heat well due to the mobility of the sea of delocalised electrons. When a part of the metal is heated, the kinetic energy is transferred throughout the electron sea, which makes metals conduct heat rapidly.

  • malleable and ductile (the ability to be deformed without breaking/separating)

Metals can be easily deformed without breaking because, unlike ionic bonds, they do not consist of negative elements, which means that shifts in movement do not make the structure separate and the sea of delocalised electrons can continue to hold the structure together.

Pretty much all related to the sea of delocalised electrons


Covalent Bonding

  • Draw electron-dot diagrams for small molecules that conform to the octet rule

Keep in mind that electron dot and Lewis dot are the same thing. Cross and dot is also used for the same purpose with slightly different execution.

With 2 hydrogen elements as an example, it is common to represent a bond with a line, with a single line representing a single bond, two lines representing a double bond, and so on. 

These are all examples of electron dot diagrams for covalent bonds. Only the valence electrons are to be drawn, and the positioning of the elements show the sharing of the electrons. 

  • Describe the bonding and structure for a covalent substance (including covalent molecular and covalent network substances)

Bonds: In covalent bonds, atoms share electrons. This is so that they can have a full outer shell to become stable. Depending on the number of shared electron pairs, covalent bonds can have single double or triple pairs.

Structure: The structure of a covalent bond varies with factors such as the number of elements and lone pairs.

Lone pair: a pair of valence electrons that are not shared with another atom in a covalent bond.

VSEPR Theory: stands for valence shell electron pair repulsion theory. Which is used to predict the shapes of molecules, consisting of linear, trigonal planar, tetrahedral, trigonal bipyramidal and octahedral.


  • Explain the physical properties of covalent molecular substances using the model of a covalent molecular substance, including:

    • low melting and boiling points

Covalent substances have low melting points because they are held together by covalent bonds within each molecule. However, the forces between these molecules are much weaker than covalent bonds which are weak points in the bond making it take less energy to turn into a liquid (melting)

The same can be said about the low boiling temperature required, because it takes less energy to separate the molecules into gas.

  • poor conductors of electricity 

Unlike metallic bonds, covalent substances are poor conductors of electricity because they do not have free-moving electrons available to conduct electricity.

  • Explain the physical properties of covalent network substances (including graphite, diamond and silica) using the model of a covalent network substance, including:

    • very high melting points

Covalent molecular substances: covalent substances consisting of 2 elements

Covalent network substances: basically the lattice structure of a covalent bond. Except it is not a cube.

Covalent network substances, compared to covalent molecular substances, have pretty much the opposite melting points and boiling points. Instead of having low melting and boiling points, they have very high melting points and boiling points. This is because compared to covalent molecular substances, they have lots more atoms held together which therefore makes the bonds stronger, along the fact that there are a shit ton more bonds that need to be broken compared to covalent molecular substances.

  • poor conductors of electricity (with the exception of graphite)

The same reason for covalent molecular substances they do not have free electrons to conduct electricity.


  • Assign a chemical formula and name for simple binary covalent compounds.

Binary covalent compound: a chemical compound composed of two different nonmetal elements bound together by covalent bonds.

Chemical formula: chemical notation + quantity (displayed as a subscript)


Chemical name: prefixes are used to identify the quantity of each element. Mono is often omitted for the first element in binary covalent compounds. For example: CO: carbon monoxide.

Prefix Number of Atoms

Mono- 1

Di- 2

Tri- 3

Tetra- 4

Penta- 5

Hexa- 6

Hepta- 7

Octa- 8

Nona- 9

Deca- 10

  • State the VSEPR theory and explain how it helps determine the shape of small molecules (elements and binary covalent compounds)

VSEPR Theory: Valence Shell Electron Pair Repulsion Theory. Basically used to predict the structure of covalent compounds.

The theory states that the 3D shape of covalent compounds can be predicted because of factors such as electron pairs and lone pairs. The theory also states that electron pairs repel each other due to them having the same charge. 

  • Name the shape of a small molecule (including linear, trigonal planar, trigonal pyramidal, v-shaped and tetrahedral)

Linear: 180-degree bond angle. Consists of 2 elements bonding with one. Since electrons have the same charge and they tend to repel each other, they will naturally go far away as possible from each other, which is 180 degrees.


Trigonal Planar: 120-degree bond angle. Consists of 3 elements bonding with one. Since electrons have the tendency to be as far away as possible from them, 120-degrees is the optimal distance between each of them. 


Tetrahedral: 109.5-degree bond angle. Consists of 4 elements bonding with one. Looks like a trigonal planar but with an element on the top of it. Again, it is the most optimal spacing between the elements. 


Trigonal pyramidal: 107.3-degree bond angle. Consists of 3 elements bonding with one. Looks like a tetrahedral except it’s missing the top element. This is simply because there are 3 bonds but a lone bond on the top which also repels the electrons. 


V-shaped/bent: either 120-degrees or 109.5-degrees. Consists of 2 elements bonded with one. It is bent because there are lone pairs.