- Created by: manasi_12345
- Created on: 22-05-20 16:46
Atoms tend to lose or gain electrons to form a full outer shell.
An ion is a charged particle. They are formed when atoms gain or lose electrons to form a full outer shell. Ions are charged because the number of protons is different from the number of electrons.
A molecular ion is a particle made of more than one atom that has an overall positive or negative charge.
- A negative ion is called an anion.
- A position ion is called a cation.
Simple ions have full outer shells, and the stable electronic configuration of the noble gases.
forming negative and positive ions
Forming negative and positive ions
Forming negative ions (anions)
Atoms gain electrons in their outer shell when they form negative ions, called anions. These ions are negative because they contain more electrons than protons.
Forming positive ions (cations)
Atoms lose electrons from their outer shell when they form positive ions, called cations. These ions are positive because they contain more protons than electrons.
Ionic bonding occurs in compounds that contain a metal (usually a Group 1 or 2 elements) with a non-metal (usually a Group 6 or 7 element). They bond to form metal compounds.
When forming an ionic compound:
- electrons are transferred from the metal atom to the non-metal atom.
- this forms oppositely-charged ions.
- the metal ion has a positive charge.
- the non-metal ion has a negative charge.
- an ionic bond is the attraction between these oppositely-charged ions.
- ionic bonding is strong and requires substantial amounts of energy to break.
Dot and cross diagrams to show formation of ions
Dot and cross diagrams help us to model when ions are formed from atoms.
Here’s an example using sodium and chlorine. They form ions which bond to form sodium chloride.
1. Draw the electronic configuration of each atom – one element with dots and the other with crosses.
2. Work out how many electrons need to be transferred.
A covalent bond is formed when two atoms share electrons to obtain a noble gas configuration. Covalent bonding occurs between non-metal atoms.
Covalent bonds are strong and require substantial amounts of energy to break.
Covalent bond: a shared pair of electrons.
Molecule: two or more atoms covalently bonded together.
Diatomic: two atoms covalently bonded together in a molecule. O2, N2 and Cl2 are examples of diatomic molecules.
drawing convalent bonding diagram
Dot and cross diagrams for covalent bonding
We can use dot and cross diagrams to show how a pair of electrons forms a covalent bond.
Here is the dot and cross diagram for oxygen (O2), a diatomic molecule. Notice the lone pairs of electrons and the two shared pairs of electrons.
There are different kinds of covalent bonds:
- a single covalent bond is when two atoms share a single pair of electrons. Represented by a single line (–).
- a double covalent bond is when two atoms share two pairs of electrons. Represented by a double line (＝).
- a triple covalent bond is when two atoms share three pairs of electrons. Represented by a triple line (≡).
The table below shows several molecules with double and triple covalent bonds.
re the dot and cross diagrams for some other common molecules.
Metallic bonding is the attraction between the positive ions in a regular lattice and the delocalised electrons. Delocalised electrons are free to move throughout the whole structure.
When drawing a diagram of a metal’s structure, be sure to draw the ions in regular rows.