Ions & Ionic Bonds (CIE IGCSE Chemistry)
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The Formation of Ions
Ionic Bonding
- An ion is an electrically charged atom or group of atoms formed by the loss or gain of electrons
- An atom will lose or gain electrons to become more stable
- The loss or gain of electrons takes place to gain a full outer shell of electrons which is a more stable arrangement of electrons
- The electronic configuration of an ion will be the same as that of a noble gas – such as helium, neon and argon
Formation of positively charged sodium ion
Formation of negatively charged chloride ion
Ionisation of metals and non-metals
- Metals: all metals can lose electrons to other atoms to become positively charged ions, known as cations
- Non-metals: all non-metals can gain electrons from other atoms to become negatively charged ions, known as anions
What is Ionic Bonding?
Ionic Bonding Definition
- Ionic compounds are formed when metal atoms react with non-metal atoms
- Metal atoms lose their outer electrons which the non-metal atoms gain to form positive and negative ions
- The positive and negative ions are held together by strong electrostatic forces of attraction between opposite charges
- This force of attraction is known as an ionic bond and they hold ionic compounds together
Ionic Bonding Examples
Dot-and-cross diagrams
- Dot and cross diagrams are diagrams that show the arrangement of the outer-shell electrons in an ionic or covalent compound or element
- The electrons are shown as dots and crosses
- In a dot and cross diagram:
- Only the outer electrons are shown
- The charge of the ion is spread evenly which is shown by using brackets
- The charge on each ion is written at the top right-hand corner
Electrostatic forces between the positive Na ion and negative Cl ion
Ionic Bonds between Group I & Group VII Elements
Example: Sodium Chloride, NaCl
Ionic Bonding Diagram
Sodium chloride ionic bonding
Explanation
- Sodium is a Group I metal so will lose one outer electron to another atom to gain a full outer shell of electrons
- A positive sodium ion with the charge 1+ is formed
- Chlorine is a Group VII non-metal so will need to gain an electron to have a full outer shell of electrons
- One electron will be transferred from the outer shell of the sodium atom to the outer shell of the chlorine atom
- A chlorine atom will gain an electron to form a negatively charged chloride ion with a charge of 1-
- The oppositely charged ions are held together by strong electrostatic forces of attraction
- The ionic compound has no overall charge
Formula of ionic compound: NaCl
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