5.2.1 Ionic bonding
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5.2.1.2 Ionic bonding
The non-metal atoms in group 0 (noble gases) are inert (unreactive)
because they have a full outer shell or a stable electron configuration.
For example neon (Ne) and argon (Ar) are non-metal atoms in group 0 (noble gases).
Ne has 10 electrons so it has the stable electronic configuration 2, 8
Ar has 18 electrons so it has the stable electron configuration 2, 8, 8
Q1. Why are noble gases unreactive?
Because they have a full outer shell / stable electron configuration.
Q2. What group are the noble gases in?
Group 0.
Q3. Give two examples of noble gases.
Any from helium, neon and argon.
Q4. What is the electron configuration of neon (Ne)?
2, 8
Q5. What is the electron configuration of argon (Ar)?
2, 8, 8
When a metal atom reacts with a non-metal atom, electrons from the outer shell of the metal atom are transferred to the outer shell of the non-metal atom.
Metal atoms lose electrons to become positively charged ions.
Non-metal atoms gain electrons to become negatively charged ions.
The oppositely charged ions (positive and negative) are held together by a strong electrostatic force of attraction called ionic bond.
Q6. What happens when a metal reacts with a non-metal?
Electrons are transferred from the outer shell of the metal atom to the outer shell of non-metal atom.
Q7. What happens to the metal atom during ionic bonding?
The metal atom loses electrons and becomes a positively charged ion.
Q8. What happens to the non-metal atom during ionic bonding?
The non-metal atom gains electrons and becomes a negatively charged ion.
Q9. What type of attraction holds the ions together in an ionic bond?
Electrostatic attraction between oppositely charged ions.
Q10. Ionic bonding happens between …
Metal and non-metal atoms.
The charge on metal ions:
a group 1 metal atom loses 1 electron from its outer shell and forms a 1+ ion
a group 2 metal atom loses 2 electrons from its outer shell and forms a 2+ ion
a group 3 metal atom loses 3 electrons from its outer shell and forms a 3+ ion
The ions produced by metals in Groups 1, 2 and 3
have a full outer shell or the stable electronic structure of a noble gas (Group 0).
Q11. What charge ion does a group 1 metal atom form?
1+
Q12. How many electrons does a group 1 metal lose?
One
Q13. When lithium atom from group 1 forms an ion, what charge would the lithium ion have?
Q13. When lithium atom from group 1 forms an ion, what charge would the lithium ion have?
Li+
Feedback: lithium atom has lost 1 electron
Q14. What charge ion does a group 2 metal atom form?
2+
Q15. How many electrons does a group 2 metal lose?
Two
Q16. When a magnesium atom from group 2 forms an ion, what charge would the magnesium ion have?
Q16. When a magnesium atom from group 2 forms an ion, what charge would the magnesium ion have?
Mg2+
Feedback: magnesium atom loses two electrons from the outer shell
Q17. What charge ion does a group 3 metal atom form?
3+
Q18. How many electrons does a group 3 metal lose?
Three.
Q19. When an aluminium atom from group 3 forms an ion, what charge would the aluminium ion have?
Q19. When an aluminium atom from group 3 forms an ion, what charge would the aluminium ion have?
Al3+
Feedback: aluminium atom loses three electrons from the outer shell
The charge on non-metal ions:
a group 6 non-metal atom gains 2 electrons on its outer shell and forms a 2- ion
a group 7 non-metal gains 1 electron on its outer shell and forms a 1- ion
The ions produced by non-metals in Groups 6 and 7
have a full outer shell or the stable electronic structure of a noble gas (Group 0).
Q20. What charge ion does a group 6 non-metal atom form?
2 –
Q21. How many electrons does a group 6 non-metal gain?
Two
Q22. When an oxygen atom from group 6 forms an ion, what charge would the oxide ion have?
O2-
Feedback: oxygen atom gains two electrons on the outer shell
Q23. What charge ion does a group 7 non-metal atom form?
1 –
Q24. How many electrons does a group 7 non-metal gain?
One
Q25. When a fluorine atom from group 7 forms an ion, what charge would the fluoride ion have?
F -
Feedback: fluorine atom gains 1 electron on the outer shell
Q26. After gaining or losing electrons, what structure do the ions achieve?
The stable electronic structure of a noble gas.
Q27. Which groups form ions with the stable electronic structures of noble gases?
Metals in groups 1, 2 and 3 and non-metals in groups 6 and 7.
Q28. Describe what happens during ionic bonding. Use key words such as atoms, electrons and ions in your answer. (4 marks)
The metal atom transfers electrons from its outer shell to the non-metal atom.
By losing electron(s) the metal atom becomes a positively charged ion with a full outer shell.
By gaining electron(s) the non-metal atom becomes a negatively charged ion with a full outer shell.
The electron transfer during the formation of an ionic compound can be represented by a dot and cross diagram
e.g. for sodium chloride.
Sodium atom transfers one electron to chlorine atom.
(Sodium loses one electron and chlorine gains one electron)
Sodium atom forms a positive ion Na+ and chlorine atom forms a negative ion Cl- (chloride ion).
Both ions achieve a full outer shell or the stable electron configuration of noble gases.
An ionic bond is formed between oppositely charged ions (Na+ and Cl-)
Q29. The diagram below shows how magnesium and iodine atoms form magnesium iodide.
Use the diagram to help you to answer this question.
Describe, in terms of electrons, what happens when magnesium reacts with iodine.
To gain full marks you should use the words atom, electron and ion in your answer. (4 marks)
Magnesium atom loses two electrons, and each iodine atom gains 1 electron
Magnesium atom forms a positive ion Mg2+ and each iodine atom forms a negative ion I- (iodide ion).
Both ions achieve a full outer shell or the stable electron configuration of noble gases.
An ionic bond is formed between oppositely charged ions (Mg2+ and I-)
Practice questions
PQ1. Explain how the magnesium atom forms a magnesium ion.
Magnesium atom (group 2) with the electronic configuration 2, 8, 2 loses 2 electrons to achieve a stable electronic configuration 2, 8.
PQ2. Explain how the fluorine atom forms a fluoride ion.
Fluorine atom (group 7) with the electronic configuration 2, 7 gains 1 electrons to achieve a stable electronic configuration 2, 8.
PQ3. The electronic structure of a potassium atom is 2,8,8,1
Figure below represents the electronic structure of a potassium ion.
What is the charge on a potassium ion?
1 +
PQ4. Figure below represents a beryllium ion.
What is the relative charge on a beryllium ion?
2+
PQ5. A magnesium atom reacts to produce a magnesium ion.
Which diagram shows a magnesium ion?
the 1st one
Feedback: Magnesium atom loses 2 electrons, so the charge on the ion is 2+
PQ6. A chlorine atom reacts to produce a chloride ion.
Which diagram shows a chloride ion?
the 2nd one (middle one)
Feedback: a chloride ion would have the electronic configuration 2, 8, 8
PQ7. When an aluminium atom (Al) turns into an aluminium ion (Al3+), does it lose or gain 3 electrons?
Aluminium atom loses 3 electrons
Feedback: Aluminium atom has the electronic structure 2, 8, 3 so it loses 3 electrons to achieve a stable electronic structure 2, 8.
PQ8. When an oxygen atom (O) turns into an oxide ion (O2–), does it lose or gain electrons? How many?
Oxygen atom gains 2 electrons.
Feedback: oxygen atom has the electronic configuration 2,6 so it gains 2 electrons to achieve a stable electronic structure 2, 8.
PQ9. Metal atoms react with non-metal atoms to form ions.
Which group of elements does not form ions?
Noble gases
PQ 10. Potassium can be reacted with iodine to produce potassium iodide.
potassium + iodine → potassium iodide
The diagram below shows how this happens. Only the outer electrons are shown.
a. A potassium atom changes into a potassium ion by ...
losing 1 electron from its outer shell.
b. An iodine atom changes into a iodide ion by ...
gaining 1 electron on its outer shell.
PQ 11. The figure below shows the electronic structure of an oxygen atom and a calcium atom.
a. A calcium atom changes into a calcium ion by ...
losing 2 electrons from its outer shell.
b. What is the charge on the calcium ion?
2+
c. An oxygen atom changes into a oxide ion by ...
gaining 2 electrons on its outer shell.
d. What is the charge on the oxide ion?
2-
PQ 12. Potassium reacts with chlorine to produce potassium chloride (KCl).
Figure below shows what happens to the electrons in the outer shells when a potassium atom reacts with a chlorine atom. The dots (o) and crosses (×) represent electrons.
Describe what happens when a potassium atom reacts with a chlorine atom to produce potassium chloride. Answer in terms of electrons. (4 marks)
Potassium atom transfers one electron to chlorine atom.
(Potassium loses one electron and chlorine gains one electron)
Potassium atom forms a positive ion K+ and chlorine atom forms a negative ion Cl- (chloride ion).
Both ions achieve a full outer shell or the stable electron configuration of noble gases.
An ionic bond is formed between oppositely charged ions (K+ and Cl-)
PQ 13. Lithium reacts with chlorine to produce lithium chloride.
Figure below shows what happens to the electrons in the outer shells when a lithium atom reacts with a chlorine atom. The dots (o) and crosses (x) represent electrons.
Describe what happens to a lithium atom and to a chlorine atom when they react.
Use Figure above to answer in terms of electrons. (4 marks)
Lithium atom transfers one electron to chlorine atom.
(Lithium loses one electron and chlorine gains one electron)
Lithium atom forms a positive ion Li+ and chlorine atom forms a negative ion Cl- (chloride ion).
Both ions achieve a full outer shell or the stable electron configuration of noble gases.
An ionic bond is formed between oppositely charged ions (Li+ and Cl-)
PQ 14. Explain what happens to sodium atoms and to oxygen atoms when sodium reacts with oxygen to produce sodium oxide (Na2O). Answer in terms of electrons. (4 marks)
1. There are two sodium atoms to one oxygen atom
2. Each sodium atom loses one electron and forms a positive ion Na+
3. Oxygen atom gains two electrons and forms a negative ion O2- (oxide ion).
4. The ions formed have a full outer shell or the stable electron configuration of noble gases.
5. An ionic bond is formed between oppositely charged ions (Na+ and O2-)
PQ 15. Caesium is in Group 1 of the periodic table.
Explain what happens to caesium atoms and to oxygen atoms when caesium reacts with oxygen to produce caesium oxide. Answer in terms of electrons. (4 marks)
1. There are two caesium atoms to one oxygen atom
2. Each caesium atom loses one electron and forms a positive ion Cs+
3. Oxygen atom gains two electrons and forms a negative ion O2- (oxide ion).
4. The ions formed have a full outer shell or the stable electron configuration of noble gases.
5. An ionic bond is formed between oppositely charged ions (Cs+ and O2-)
PQ 16. Magnesium chloride contains magnesium ions (Mg2+) and chloride ions (Cl⁻). Describe, in terms of electrons, what happens when a magnesium atom reacts with chlorine atoms to produce magnesium chloride. (4 marks)
1. There are two chlorine atoms to one magnesium atom
2. Magnesium atom loses two electrons and forms a positive ion Mg2+
3. Each chlorine atom gains one electron and form a negative ion Cl- (chloride ion).
4. The ions formed have a full outer shell or the stable electron configuration of noble gases.
5. An ionic bond is formed between oppositely charged ions (Mg 2+ and Cl-)
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