Chemical Bonding and Structure
A. Chemical Bonding
A chemical bond is formed when atoms of the same or different elements share, gain, donate, or delocalize their outer energy level electrons to combine during chemical reactions in order to become stable.
Atoms have an equal number of negatively charged electrons in the energy levels and positively charged protons in the nucleus.
Atoms are chemically stable if they have filled outer energy levels. An energy level is full if it has a duplet (2) or octet (8) electrons in the outer energy level.
Noble gases have a duplet or octet. All other atoms try to be like noble gases through chemical reactions and forming molecules.
Only electrons in the outer energy level take part in the formation of a chemical bond. There are three main types of chemical bonds formed by atoms:
- (i) Covalent bond
- (ii) Ionic/electrovalent bond
- (iii) Metallic bond
(i) Covalent Bond
A covalent bond is formed when atoms of the same or different elements share some or all the outer energy level electrons to combine during chemical reactions in order to attain a duplet or octet.
A shared pair of electrons is attracted by the nucleus (protons) of the two atoms sharing.
Covalent bonds are mainly formed by non-metals to form molecules. A molecule is a group of atoms of the same or different elements held together by a covalent bond. The number of atoms making a molecule is called atomicity. Noble gases are monatomic because they are stable and thus do not bond with each other or other atoms. Most other gases are diatomic.
The more the number of electrons shared, the stronger the covalent bond.
A pair of electrons that do not take part in the formation of a covalent bond is called a lone pair of electrons.
Mathematically, the number of electrons to be shared by an atom is equal to the number of electrons remaining for the atom to be stable/attain duplet/octet/have maximum electrons in the outer energy level.
The following diagrams illustrate the formation of covalent bonds:
a) Hydrogen molecule is made up of two hydrogen atoms in the outer energy level, each requiring one electron to have a stable duplet.
To show the formation of covalent bonding in the molecule, the following data/information is required:
| Symbol of atom/element taking part in bonding | H | H |
| Number of protons/electrons | 1 | 1 |
| Electron configuration/structure | 1: | 1: |
| Number of electrons in outer energy level | 1 | 1 |
| Number of electrons remaining to be stable/shared | 1 | 1 |
| Number of electrons not shared (lone pairs) | 0 | 0 |
Diagram method 2
H H
Note:
After bonding, the following intermolecular forces exist:
- The attraction of the shared electrons by both nuclei/protons of the atoms.
- The repulsion of the nucleus of one atom on the other.
- Balance of the attraction and repulsion is maintained inside/intermolecular/within the molecule as follows:
E1
P1 P1
E1
(iv) Protons (P1) from nucleus of atom 1 repel protons (P2) from nucleus of atom 2.
(v) Electron (E1) in the energy levels of atom 1 repel electron (E2) in the energy levels of atom 2.
(vi) Protons (P1) from nucleus of atom 1 attract electron (E2) in the energy levels of atom 2.
(vii) Protons (P2) from nucleus of atom 2 attract electron (E1) in the energy levels of atom 1.
b) Fluorine, chlorine, bromine, and iodine molecules are also made up of two atoms sharing the outer energy level electrons to have a stable octet.
To show the formation of covalent bonding in the molecule, the following data/information is required:
(i) Fluorine
| Symbol of atom/element taking part in bonding | F | F |
| Number of protons/electrons | 9 | 9 |
| Electron configuration/structure | 2:7 | 2:7 |
| Number of electrons in outer energy level | 7 | 7 |
| Number of electrons remaining to be stable/shared | 1 | 1 |
| Number of outer electrons not shared (3 lone pairs) | 6 | 6 |
Diagram method 2
(ii) Chlorine
| Symbol of atom/element taking part in bonding | Cl | Cl |
| Number of protons/electrons | 17 | 17 |
| Electron configuration/structure | 2:8:7 | 2:8:7 |
| Number of electrons in outer energy level | 7 | 7 |
| Number of electrons remaining to be stable/shared | 1 | 1 |
| Number of outer electrons not shared (3 lone pairs) | 6 | 6 |
Diagram method 2
(iii) Bromine
| Symbol of atom/element taking part in bonding | Br | Br |
| Number of protons/electrons | 35 | 35 |
| Electron configuration/structure | 2:8:18:7 | 2:8:18:7 |
| Number of electrons in outer energy level | 7 | 7 |
| Number of electrons remaining to be stable/shared | 1 | 1 |
| Number of outer electrons not shared (3 lone pairs) | 6 | 6 |
Diagram method 2
(iv) Iodine
| Symbol of atom/element taking part in bonding | I | I |
| Number of protons/electrons | 53 | 53 |
| Electron configuration/structure | 2:8:18:18:7 | 2:8:18:18:7 |
| Number of electrons in outer energy level | 7 | 7 |
| Number of electrons remaining to be stable/shared | 1 | 1 |
| Number of outer electrons not shared (3 lone pairs) | 6 | 6 |
Diagram method 2
c) Oxygen molecule is made up of two atoms sharing each two outer energy level electrons to have a stable octet as shown below:
| Symbol of atom/element taking part in bonding | O | O |
| Number of protons/electrons | 8 | 8 |
| Electron configuration/structure | 2:6 | 2:6 |
| Number of electrons in outer energy level | 6 | 6 |
| Number of electrons remaining to be stable/shared | 2 | 2 |
| Number of outer electrons not shared (2 lone pairs) | 4 | 4 |
Diagram method 2
d) Nitrogen and phosphorus molecules are made up of two atoms sharing each three outer energy level electrons to have a stable octet as shown below:
(i) Nitrogen
| Symbol of atom/element taking part in bonding | N | N |
| Number of protons/electrons | 7 | 7 |
| Electron configuration/structure | 2:5 | 2:5 |
| Number of electrons in outer energy level | 5 | 5 |
| Number of electrons remaining to be stable/shared | 3 | 3 |
| Number of outer electrons not shared (3 lone pairs) | 2 | 2 |
Diagram method 2
(ii) Phosphorus
| Symbol of atom/element taking part in bonding | P | P |
| Number of protons/electrons | 15 | 15 |
| Electron configuration/structure | 2:8:5 | 2:8:5 |
| Number of electrons in outer energy level | 5 | 5 |
| Number of electrons remaining to be stable/shared | 3 | 3 |
| Number of outer electrons not shared (3 lone pairs) | 2 | 2 |
Diagram method 2
e) Water molecule is made up of hydrogen and oxygen. Hydrogen requires sharing one electron with oxygen to be stable/attain duplet. Oxygen requires sharing two electrons to be stable/attain octet. Two hydrogen atoms share with one oxygen atom for both to be stable as shown below:
| Symbol of atoms/elements taking part in bonding | O | H |
| Number of protons/electrons | 8 | 1 |
| Electron configuration/structure | 2:6 | 1 |
| Number of electrons in outer energy level | 6 | 1 |
| Number of electrons remaining to be stable/shared | 2 | 1 |
| Number of electrons not shared (2 Oxygen lone pairs) | 4 | 0 |
Diagram method 2
f) Ammonia molecule is made up of hydrogen and nitrogen. Hydrogen requires sharing one electron with nitrogen to be stable/attain duplet. Nitrogen requires sharing three electrons to be stable/attain octet. Three hydrogen atoms share with one nitrogen atom for both to be stable as shown below:
| Symbol of atoms/elements taking part in bonding | N | H |
| Number of protons/electrons | 7 | 1 |
| Electron configuration/structure | 2:5 | 1: |
| Number of electrons in outer energy level | 5 | 1 |
| Number of electrons remaining to be stable/shared | 3 | 1 |
| Number of electrons not shared (1 Nitrogen lone pairs) | 2 | 0 |
Diagram method 2
g) Carbon (IV) oxide molecule is made up of carbon and oxygen. Carbon requires sharing four electrons with oxygen to be stable/attain octet. Oxygen requires sharing two electrons to be stable/attain octet. Two oxygen atoms share with one carbon atom for both to be stable as shown below:
| Symbol of atoms/elements taking part in bonding | O | C |
| Number of protons/electrons | 8 | 6 |
| Electron configuration/structure | 2:6 | 2:4 |
| Number of electrons in outer energy level | 6 | 4 |
| Number of electrons remaining to be stable/shared | 2 | 4 |
| 2 lone pairs from each Oxygen atom | 2 | 0 |
Diagram method 2
h) Methane molecule is made up of hydrogen and carbon. Hydrogen requires sharing one electron with carbon to be stable/attain duplet. Carbon requires sharing four electrons to be stable/attain octet. Four hydrogen atoms share with one carbon atom for both to be stable as shown below:
| Symbol of atoms/elements taking part in bonding | C | H |
| Number of protons/electrons | 6 | 1 |
| Electron configuration/structure | 2:4 | 1 |
| Number of electrons in outer energy level | 4 | 1 |
| Number of electrons remaining to be stable/shared | 4 | 1 |
| Number of electrons not shared (No lone pairs) | 0 | 0 |
Diagram method 2
i) Tetrachloromethane molecule is made up of chlorine and carbon. Chlorine requires sharing one electron with carbon to be stable/attain octet. Carbon requires sharing four electrons to be stable/attain octet. Four chlorine atoms share with one carbon atom for both to be stable as shown below:
| Symbol of atoms/elements taking part in bonding | C | Cl |
| Number of protons/electrons | 6 | 17 |
| Electron configuration/structure | 2:4 | 2:8:7 |
| Number of electrons in outer energy level | 4 | 7 |
| Number of electrons remaining to be stable/shared | 4 | 1 |
| 3 lone pairs from each Chlorine atom (24 electrons) | 0 | 6 |
Diagram method 2
j) Ethane molecule is made up of six hydrogen and two carbon atoms. Hydrogen requires sharing one electron with carbon to be stable/attain duplet. Carbon requires sharing four electrons to be stable/attain octet. Three hydrogen atoms share with one carbon atom while another three hydrogen atoms share with a different carbon atom. The two carbon atoms bond by sharing a pair of the remaining electrons as shown below:
| Symbol of atoms/elements taking part in bonding | C | H |
| Number of protons/electrons | 6 | 1 |
| Electron configuration/structure | 2:4 | 1 |
| Number of electrons in outer energy level | 4 | 1 |
| Number of electrons remaining to be stable/shared | 4 | 1 |
| Number of electrons not shared (No lone pairs) | 0 | 0 |
Diagram method 2
k) Ethene molecule is made up of four hydrogen and two carbon atoms. Hydrogen requires sharing one electron with carbon to be stable/attain duplet. Carbon requires sharing four electrons to be stable/attain octet. Two hydrogen atoms share with one carbon atom while another two hydrogen atoms share with a different carbon atom. The two carbon atoms bond by sharing two pairs of the remaining electrons as shown below:
| Symbol of atoms/elements taking part in bonding | C | H |
| Number of protons/electrons | 6 | 1 |
| Electron configuration/structure | 2:4 | 1 |
| Number of electrons in outer energy level | 4 | 1 |
| Number of electrons remaining to be stable/shared | 4 | 1 |
| Number of electrons not shared (No lone pairs) | 0 | 0 |
Diagram method 2
l) Ethyne molecule is made up of two hydrogen and two carbon atoms. Hydrogen requires sharing one electron with carbon to be stable/attain duplet. Carbon requires sharing four electrons to be stable/attain octet. One hydrogen atom shares with one carbon atom while another hydrogen atom shares with a different carbon atom. The two carbon atoms bond by sharing three pairs of the remaining electrons as shown below:
| Symbol of atoms/elements taking part in bonding | C | H |
| Number of protons/electrons | 6 | 1 |
| Electron configuration/structure | 2:4 | 1 |
| Number of electrons in outer energy level | 4 | 1 |
| Number of electrons remaining to be stable/shared | 4 | 1 |
| Number of electrons not shared (No lone pairs) | 0 | 0 |
Diagram method 2
j) Ethanol molecule is made up of six hydrogen, one oxygen atom, and two carbon atoms.
Five hydrogen atoms share their one electron each with carbon to be stable/attain duplet. One hydrogen atom shares one electron with oxygen for both to attain duplet/octet.
Each carbon uses four electrons to share with oxygen and hydrogen to attain octet/duplet.
NB: Oxygen has two lone pairs.
j) Ethanoic molecule is made up of four hydrogen, two oxygen atoms, and two carbon atoms.
Three hydrogen atoms share their one electron each with carbon to be stable/attain duplet. One hydrogen atom shares one electron with oxygen for both to attain duplet/octet.
Each carbon uses four electrons to share with oxygen and hydrogen to attain octet/duplet.
NB: Each oxygen atom has two lone pairs.
By convention (as a rule), a:
- Single covalent bond made up of two shared (a pair) electrons is represented by a dash (–)
- Double covalent bond made up of four shared (two pairs) electrons is represented by a double dash (=)
- Triple covalent bond made up of six shared (three pairs) electrons is represented by a triple dash (≡)
The representation below shows the molecules covered in (a) to (k) above:
- Hydrogen molecule (H2): H–H
- Fluorine molecule (F2): F–F
- Chlorine molecule (Cl2): Cl–Cl
- Bromine molecule (Br2): Br–Br
- Iodine molecule (I2): I–I
- Oxygen molecule (O2): O=O
- Nitrogen molecule (N2): N≡N
- Phosphorus molecule (P2): P=P
- Water molecule (H2O): H–O–H
- Ammonia molecule (NH3): H–N–H
H - Carbon (IV) oxide molecule (CO2): O=C=O
- Methane molecule (CH4): H–C–H
H - Tetrachloromethane molecule (CCl4): Cl–C–Cl
Cl - Ethane molecule (C2H6): H–C–C–H
H H - Ethene molecule (C2H4): H–C=C–H
H H - Ethyne molecule (C2H2): H–C≡C–H
Dative / Coordinate Bond
A dative/coordinate bond is a covalent bond formed when a lone pair of electrons is donated then shared to an electron-deficient species/ion/atom.
During dative/coordinate bonding, all the shared pair of electrons are donated by one of the combining/bonding species/ion/atom.
Like covalent bonding, coordinate/dative bond is mainly formed by non-metals.
Illustration of coordinate/dative bond
a) Ammonium ion (NH4+)
The ammonium ion is made up of ammonia (NH3) molecule and hydrogen (H+) ion. The H+ ion has no electrons. NH3 is made up of covalent bonding from nitrogen and hydrogen. One lone pair of electrons is present in the nitrogen atom after the bonding. This lone pair is donated and shared with an electron-deficient H+ ion.
Diagram method 2
b) Phosphine ion (PH4+)
The phosphine ion is made up of phosphine (PH3) molecule and hydrogen (H+) ion. The H+ ion has no electrons. PH3 is made up of covalent bonding from phosphorus and hydrogen. One lone pair of electrons is present in the phosphorus atom. After the bonding, this lone pair is donated and shared with the electron-deficient H+ ion.
Diagram method 2
c) Hydroxonium (H3O+) ion
The hydroxonium ion is made up of water (H2O) molecule and hydrogen (H+) ion. The H+ ion has no electrons. The H2O molecule is made up of covalent bonding from oxygen and hydrogen. One lone pair of electrons out of the two present in the oxygen atom after the bonding is donated and shared with the electron-deficient H+ ion.
Diagram method 2
d) Carbon (II) oxide (CO)
Carbon (II) oxide is made up of carbon and oxygen atoms sharing each two outer electrons and not sharing each two electrons. Oxygen with an extra lone pair of electrons donates and shares with the carbon atom for both to be stable.
Diagram method 2
e) Aluminum (III) chloride (AlCl3/Al2Cl6)
Aluminum (III) chloride is made up of aluminum and chlorine. One aluminum atom shares its outer electrons with three separate chlorine atoms. All chlorine atoms attain stable octet but aluminum does not. Another molecule of aluminum chloride shares its chlorine lone pair of electrons with the aluminum atom for both to be stable. This type of bond exists only in vapor phase after aluminum chloride sublimes.
Diagram method 2
A dative/coordinate bond is by convention represented by an arrow (→) heading from the donor of the shared pair of electrons.
Below is the representation of molecules in the above examples:
a) Ammonium ion:
H
H− N→H
H
b) Phosphine ion:
H− P→H
H
c) Hydroxonium ion:
H− O→H
H
d) Carbon (II) oxide:
O→C
e) Aluminum (III) chloride:
Cl Cl Cl
Al Al
Cl Cl Cl
(ii) Ionic/Electrovalent Bond
An ionic/electrovalent bond is an extreme form of a covalent bond.
During ionic/electrovalent bonding, there is complete transfer of valence electrons to one electronegative atom from an electropositive atom.
All metals are electropositive and easily/readily donate/lose their valence electrons.
All non-metals are electronegative and easily/readily gain/acquire extra electrons.
Ionic/electrovalent bonding therefore mainly involves transfer of electrons from metal/metallic radical to non-metallic radical.
When an electropositive atom donates/loses the valence electrons, it forms a positively charged cation to attain stable octet/duplet.
When an electronegative atom gains/acquires extra valence electrons, it forms a negatively charged anion to attain stable octet/duplet.
The electrostatic attraction force between the stable positively charged cation and the stable negatively charged anion with opposite charges constitutes the ionic bond.
Like in covalent/dative/coordinate bonding, only the outer energy level electrons take part in the formation of ionic/electrovalent bond.
Like in covalent/dative/coordinate bonding, the more electrons involved in the formation of ionic/electrovalent bond, the stronger the ionic/electrovalent bond.
Illustration of ionic/electrovalent bond
a) Sodium chloride (NaCl)
Sodium chloride (NaCl) is formed when a sodium atom donates its outer valence electron to a chlorine atom for both to attain stable octet:
| Symbol of atoms/elements taking part in bonding | Na | Cl |
| Number of protons/electrons | 11 | 17 |
| Electron configuration/structure | 2:8:1 | 2:8:7 |
| Number of electrons in outer energy level | 1 | 7 |
| Number of electrons donated and gained to be stable | 1 | 1 |
| New electron configuration/structure | 2:8: | 2:8: |
| Symbol of cation/anion after bonding | Na+ | Cl– |
Diagram
b) Magnesium chloride (MgCl2)
Magnesium chloride (MgCl2) is formed when a magnesium atom donates its two outer valence electrons to chlorine atoms. Two chlorine atoms are required to gain each one electron. All the ions (cations and anions) attain stable octet:
| Symbol of atoms/elements taking part in bonding | Mg | Cl |
| Number of protons/electrons | 12 | 17 |
| Electron configuration/structure | 2:8:2 | 2:8:7 |
| Number of electrons in outer energy level | 2 | 7 |
| Number of electrons donated and gained to be stable | 2 | 1 |
| New electron configuration/structure | 2:8: | 2:8: |
| Symbol of cation/anion after bonding | Mg2+ | Cl– |
Diagram
c) Lithium oxide (Li2O)
Lithium oxide (Li2O) is formed when lithium atoms donate their outer valence electrons to oxygen atom. Two lithium atoms are required to donate/lose each one electron and attain stable duplet. Oxygen atom acquires the two electrons and attains stable octet:
| Symbol of atoms/elements taking part in bonding | Li | O |
| Number of protons/electrons | 3 | 8 |
| Electron configuration/structure | 2:1 | 2:6 |
| Number of electrons in outer energy level | 1 | 6 |
| Number of electrons donated and gained to be stable | 1 | 2 |
| New electron configuration/structure | 2: | 2:8: |
| Symbol of cation/anion after bonding | Li+ | O2- |
Diagram
d) Aluminum (III) oxide (Al2O3)
Aluminum (III) oxide (Al2O3) is formed when aluminum atoms donate their three outer valence electrons to oxygen atoms. Two aluminum atoms are required to donate/lose each three electrons and attain stable octet. Three oxygen atoms gain/acquire the six electrons and attain stable octet:
| Symbol of atoms/elements taking part in bonding | Al | O |
| Number of protons/electrons | 13 | 8 |
| Electron configuration/structure | 2:8:3 | 2:6 |
| Number of electrons in outer energy level | 3 | 6 |
| Number of electrons donated and gained to be stable | 3 | 2 |
| New electron configuration/structure | 2:8: | 2:8: |
| Symbol of cation/anion after bonding | Al3+ | O2- |
Diagram
e) Calcium oxide (CaO)
Calcium oxide (CaO) is formed when a calcium atom donates its two outer valence electrons to oxygen atom. Both attain stable octet:
| Symbol of atoms/elements taking part in bonding | Ca | O |
| Number of protons/electrons | 20 | 8 |
| Electron configuration/structure | 2:8:8:2 | 2:6 |
| Number of electrons in outer energy level | 2 | 6 |
| Number of electrons donated and gained to be stable | 2 | 2 |
| New electron configuration/structure | 2:8:8: | 2:8: |
| Symbol of cation/anion after bonding | Ca2+ | O2- |
Diagram
Some compounds can be formed from ionic/electrovalent, covalent, and dative/coordinate bonding within their atoms/molecules:
a) Formation of ammonium chloride:
Ammonium chloride is formed from the reaction of ammonia gas and hydrogen chloride gas. Both ammonia and hydrogen chloride gas are formed from covalent bonding. During the reaction of ammonia and hydrogen chloride gas to form ammonium chloride:
- Ammonia forms a dative/coordinate bond with electron deficient H+ ion from hydrogen chloride to form ammonium ion (NH4+).
- The chloride ion Cl– and ammonium ion (NH4+) bond through ionic/electrovalent bond from the electrostatic attraction between the opposite/unlike charges.
Diagram
b) Dissolution/dissolving of hydrogen chloride:
Hydrogen chloride is formed when hydrogen and chlorine atoms form a covalent bond. Water is formed when hydrogen and oxygen atoms also form a covalent bond. When hydrogen chloride gas is dissolved in water:
- Water molecules form a dative/coordinate bond with electron deficient H+ ion from hydrogen chloride to form hydroxonium ion (H3O+).
- The chloride ion Cl– and hydroxonium ion (H3O+) bond through ionic/electrovalent bond from the electrostatic attraction between the opposite/unlike charges.
Diagram
c) Dissolution/dissolving of ammonia gas:
Ammonia gas is formed when hydrogen and nitrogen atoms form a covalent bond. Water is formed when hydrogen and oxygen atoms also form a covalent bond. When ammonia gas is dissolved in water:
- Ammonia forms a dative/coordinate bond with electron deficient H+ ion from a water molecule to form ammonium ion (NH4+).
- The hydroxide ion OH– and ammonium ion (NH4+) bond through ionic/electrovalent bond from the electrostatic attraction between the opposite/unlike charges.
Diagram
(iii) Metallic Bond
A metallic bond is formed when metallic atoms delocalize their outer electrons in order to be stable.
Metals delocalize their outer electrons to form positively charged cations.
The electrostatic attraction force between the metallic cation and the negatively charged electrons constitutes the metallic bond.
The more delocalized electrons, the stronger the metallic bond.
Illustration of metallic bond
a) Sodium (Na) is made of one valence electron. The electron is donated to form Na+ ion. The electron is delocalized/free within many sodium ions.
| Symbol of atoms/elements taking part in bonding | Na | Na | Na |
| Number of protons/electrons | 11 | 11 | 11 |
| Electron configuration/structure | 2:8:1 | 2:8:1 | 2:8:1 |
| Number of electrons in outer energy level | 1 | 1 | 1 |
| Number of electrons delocalized/free within | 1 | 1 | 1 |
| New electron configuration/structure | 2:8: | 2:8: | 2:8: |
| Symbol of cation after metallic bonding | Na+ | Na+ | Na+ |
Diagram
(three) Metallic cations attract (three) free/delocalized electrons.
b) Aluminium (Al) is made of three valence electrons. The three electrons are donated to form Al3+ ion. The electrons are delocalized/free within many aluminium ions.
| Symbol of atoms/elements taking part in bonding | Al | Al | Al |
| Number of protons/electrons | 13 | 13 | 13 |
| Electron configuration/structure | 2:8:3 | 2:8:3 | 2:8:3 |
| Number of electrons in outer energy level | 3 | 3 | 3 |
| Number of electrons delocalized/free within | 3 | 3 | 3 |
| New electron configuration/structure | 2:8: | 2:8: | 2:8: |
| Symbol of cation after metallic bonding | Al3+ | Al3+ | Al3+ |
Diagram
(three) Metallic cations attract (nine) free/delocalized electrons.
c) Calcium (Ca) is made of two valence electrons. The two electrons are donated to form Ca2+ ion. The electrons are delocalized/free within many calcium ions.
| Symbol of atoms/elements taking part in bonding | Ca | Ca | Ca |
| Number of protons/electrons | 20 | 20 | 20 |
| Electron configuration/structure | 2:8:8:2 | 2:8:8:2 | 2:8:8:2 |
| Number of electrons in outer energy level | 2 | 2 | 2 |
| Number of electrons delocalized/free within | 2 | 2 | 2 |
| New electron configuration/structure | 2:8:8: | 2:8:8: | 2:8:8: |
| Symbol of cation after metallic bonding | Ca2+ | Ca2+ | Ca2+ |
Diagram
(three) Metallic cations attract (six) free/delocalized electrons.
d) Magnesium (Mg) is made of two valence electrons. The two electrons are donated to form Mg2+ ion. The electrons are delocalized/free within many magnesium ions.
| Symbol of atoms/elements taking part in bonding | Mg | Mg |
| Number of protons/electrons | 12 | 12 |
| Electron configuration/structure | 2:8:2 | 2:8:2 |
| Number of electrons in outer energy level | 2 | 2 |
| Number of electrons delocalized/free within | 2 | 2 |
| New electron configuration/structure | 2:8: | 2:8: |
| Symbol of cation after metallic bonding | Mg2+ | Mg2+ |
Diagram
(two) Metallic cations attract (four) free/delocalized electrons.
e) Lithium (Li) is made of one valence electron. The electron is donated to form Li+ ion. The electron is delocalized/free within many lithium ions.
| Symbol of atoms/elements taking part in bonding | Li | Li | Li | Li |
| Number of protons/electrons | 3 | 3 | 3 | 3 |
| Electron configuration/structure | 2:1 | 2:1 | 2:1 | 2:1 |
| Number of electrons in outer energy level | 1 | 1 | 1 | 1 |
| Number of electrons delocalized/free within | 1 | 1 | 1 | 1 |
| New electron configuration/structure | 2:1: | 2:1: | 2:1: | 2:1: |
| Symbol of cation after metallic bonding | Li+ | Li+ | Li+ | Li+ |
Diagram
(four) Metallic cations attract (four) free/delocalized electrons.
