Ions And Ionic Bonds

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Formation of Ions

An ion is an electrically charged atom or group of atoms formed by loss or gain of electrons.
Atoms gain or lose electrons to obtain a full outer shell (noble gas configuration).
Positive ions (cations) form when atoms lose electrons (more protons than electrons). Metals form cations.
Negative ions (anions) form when atoms gain electrons (more electrons than protons). Non-metals form anions.
Group 1 elements form 1+ ions; Group 2 form 2+ ions; Group 6 form 2– ions; Group 7 form 1– ions.

Formation of a sodium ion (cation)

Ionic Bonding

Ionic bonds form between metal and non-metal atoms via electron transfer.
Metal atoms lose electrons to become positive ions; non-metal atoms gain electrons to become negative ions.
The oppositely charged ions are held together by strong electrostatic forces of attraction – this is the ionic bond.
Ionic compounds have no overall charge (total positive charge = total negative charge).
Example: NaCl – Na loses one electron to form Na⁺, Cl gains one electron to form Cl⁻.

Sodium loses one electron and chlorine gains an electron

Dot-and-Cross Diagrams

Dot-and-cross diagrams show outer-shell electrons only (dots for one atom, crosses for the other).
Each ion is enclosed in square brackets with the charge written at the top right.
Example: NaCl – Na⁺ has no outer electrons; Cl⁻ has eight outer electrons.
Example: MgO – Mg loses two electrons to form Mg²⁺; O gains two electrons to form O²⁻.

Ionic bonding in sodium chloride

Lattice Structure (Extended Tier)

Ionic compounds form a giant lattice structure – a regular, repeating 3D arrangement of alternating positive and negative ions.
The lattice is held together by strong electrostatic forces in all directions.
Example: NaCl lattice consists of Na⁺ and Cl⁻ ions arranged alternately.

The lattice structure of NaCl

Properties of Ionic Compounds

Ionic compounds are solid at room temperature and have high melting and boiling points.
High melting/boiling points are due to strong electrostatic forces in the giant lattice requiring much energy to overcome.
Solid state: poor electrical conductors because ions are fixed in the lattice and cannot move.
Molten or aqueous state: good conductors because ions are free to move and carry charge.
Greater ion charges (e.g., Mg²⁺ and O²⁻) lead to stronger forces and higher melting points than singly charged ions (e.g., Na⁺ and Cl⁻).

Electrical conductivity of ionic compounds

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練習題

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1.What is an ion?
Easy
- AAn atom with a full outer shell
- BAn electrically charged atom or group of atoms
- CA neutral atom
- DA molecule
2.What is the name for a positive ion?
Easy
3.What is the name for a negative ion?
Easy
4.Complete the sentence:
Easy
An atom that loses electrons becomes a ____ ion.
5.All metals lose electrons to become positively charged ions.
Easy
True or false?
6.What is the charge on an ion formed from a Group 2 element?
Easy
- A3
- B4
- C1
- D2
7.Which of the following describes the structure of an ionic compound?
Medium
- AA giant lattice of alternating positive and negative ions
- BA simple molecular structure
- CA giant covalent structure
- DA lattice of atoms held by metallic bonds
8.Ionic compounds conduct electricity in the solid state.
Easy
True or false?

更多題目

9.Why do ionic compounds have high melting points?
Medium
10.What is the charge on the magnesium ion in magnesium oxide?
Easy
- A3
- B2
- C1
- D4
11.Which of the following ionic compounds is expected to have the highest melting point?
Medium
- ANaCl
- BMgO
- CKCl
- DCaCl2
12.Non-metals gain electrons to become negatively charged ions.
Easy
True or false?
13.An ion is formed when an atom:
Easy
- Aloses or gains protons
- Bloses or gains electrons
- Cshares electrons with another atom
- Dloses or gains neutrons
14.Match each group of the periodic table to the charge on the ion formed by elements in that group.
Medium
- Group 1
- Group 2
- Group 6
- Group 7
- 1+
- 2+
- 2−
- 1−
15.Which of the following are properties of ionic compounds? (Select all that apply)
Medium
- AHigh melting points
- BConduct electricity in the solid state
- CConduct electricity when molten or dissolved
- DLow boiling points
- EFormed between metals and non-metals
16.Arrange the following steps in the correct order to describe the formation of an ionic bond between sodium and chlorine.
Medium
- Electrostatic attraction holds Na⁺ and Cl⁻ together
- Sodium atom loses one electron to become Na⁺
- Chlorine atom gains one electron to become Cl⁻
- Sodium and chlorine atoms approach each other
17.In an ionic compound, the overall charge is zero.
Easy
True or false?
18.Which of the following best describes the structure of an ionic compound?
Medium
- AA regular arrangement of molecules held by weak forces
- BA giant lattice of alternating positive and negative ions
- CA random arrangement of atoms held by covalent bonds
- DA giant structure of atoms held by delocalised electrons
19.Which of the following statements about magnesium oxide (MgO) are correct? (Select all that apply)
Medium
- AIt has a higher melting point than sodium chloride
- BIt contains Mg⁺ and O⁻ ions
- CIt conducts electricity when molten
- DIt is a gas at room temperature
20.Arrange the following ionic compounds in order of increasing melting point (lowest first).
Medium
- NaCl
- MgO
- KCl
21.An atom of calcium (atomic number 20) forms an ion. What is the electronic configuration of the calcium ion?
Medium
- A2,8,8,2
- B2,8,8
- C2,8,8,1
- D2,8,8,0
22.Which of the following elements is most likely to form a 2− ion?
Medium
- ASodium
- BOxygen
- CAluminium
- DChlorine
23.In a dot-and-cross diagram for an ionic compound, the charge on each ion is written at the top right-hand corner, inside the square brackets.
Medium
True or false?
24.Which of the following statements about the properties of ionic compounds are correct? (Select all that apply)
Medium
- AThey conduct electricity in the solid state.
- BThey have high melting points.
- CThey are usually soluble in water.
- DThey are soft and malleable.
- EThey conduct electricity when molten.
25.Match each element to the charge on its ion.
Easy
- Magnesium
- Oxygen
- Sodium
- Chlorine
- 1+
- 2+
- 1−
- 2−
26.Ionic compounds conduct electricity in the solid state because the ions are free to move.
Easy
True or false?
27.In an experiment to test the electrical conductivity of an ionic compound, the compound does not conduct electricity when solid but conducts when molten. Which statement explains this observation?
Medium
- AIn the solid state, the ions are fixed in the lattice and cannot move; in the molten state, the ions are free to move and carry charge.
- BIn the solid state, the ions are free to move; in the molten state, the ions are fixed in the lattice.
- CIn the solid state, the compound has no ions; in the molten state, ions are formed.
- DIn the solid state, the electrons are free to move; in the molten state, the electrons are fixed.
28.A student is investigating the melting points of two ionic compounds: sodium chloride (NaCl) and magnesium oxide (MgO). Which compound has the higher melting point and why?
Medium
- AMgO, because the Mg2+ and O2- ions have higher charges than Na+ and Cl-, leading to stronger electrostatic forces.
- BNaCl, because sodium is more reactive than magnesium.
- CMgO, because it has a larger formula mass.
- DNaCl, because the ions are smaller and pack more tightly.
29.Which of the following are correct statements about the dot-and-cross diagram for magnesium oxide (MgO)? (Select all that apply)
Medium
- AThe magnesium atom loses two electrons.
- BThe oxygen atom gains two electrons.
- CThe magnesium ion is written with a 2- charge.
- DThe oxygen ion is written with a 2- charge.
- EThe diagram shows only the outer shell electrons.
30.What is the charge on an ion formed from a Group 6 element?
Easy
- A1+
- B2+
- C2−
- D1−
31.An anion is a positively charged ion.
Easy
True or false?
32.Which of the following describes the electronic configuration of a sodium ion (Na⁺)?
Easy
- A2,8,1
- B2,8
- C2,7
- D2,8,8
33.All non-metals gain electrons to become negatively charged ions.
Easy
True or false?
34.Which of the following statements about the dot-and-cross diagram for magnesium oxide (MgO) are correct? (Select all that apply)
Medium
- AThe magnesium ion has a 2+ charge.
- BThe oxygen ion has a 2− charge.
- CBoth ions are shown with square brackets.
- DThe diagram shows only the inner electrons.
35.A student measures the electrical conductivity of three ionic compounds: NaCl, MgO, and CaCl₂. The results show that MgO has the highest melting point. Which is the best explanation?
Medium
- AMgO has the smallest ions, so the lattice is more compact.
- BMgO has ions with higher charges (Mg²⁺ and O²⁻), leading to stronger electrostatic forces.
- CMgO is a covalent compound, so it has stronger bonds.
- DMgO has a simple molecular structure, making it harder to melt.
36.Which of the following compounds is most likely to be magnesium oxide (MgO), based on its melting point?
Medium
- ACompound A: 801 °C
- BCompound B: 1410 °C
- CCompound C: 2852 °C
- DCompound D: 772 °C
37.When an atom of a Group 7 element forms an ion, it gains one electron.
Easy
True or false?
38.Which of the following are correct about the dot-and-cross diagram for magnesium oxide (MgO)? (Select all that apply)
Medium
- AMagnesium loses two electrons.
- BOxygen gains two electrons.
- CThe magnesium ion has a 2− charge.
- DThe oxygen ion has a 2+ charge.
- EBoth ions have full outer shells.
39.Match each element to the charge on the ion it typically forms.
Easy
- Calcium
- Oxygen
- Chlorine
- 2+
- 2−
- 1−
40.Arrange the following steps in the correct order to describe the formation of an ionic bond between a sodium atom and a chlorine atom.
Medium
- The sodium ion and chloride ion are held together by electrostatic forces.
- A sodium atom loses one electron to become a Na⁺ ion.
- A chlorine atom gains one electron to become a Cl⁻ ion.
- The oppositely charged ions attract each other.
41.A student is given three white solids: A, B, and C. They test electrical conductivity. All are non-conductors as solids. When melted, A and B conduct electricity but C does not. Which is most likely an ionic compound?
Medium
- AOnly A and B
- BOnly C
- CAll three
- DNone
42.A student tests the electrical conductivity of sodium chloride in three states: solid, molten, and aqueous solution. In which state(s) does sodium chloride conduct electricity?
Medium
- ASolid only
- BMolten and aqueous solution only
- CAqueous solution only
- DSolid, molten, and aqueous solution
43.An ion is an atom or group of atoms that has an electrical charge due to the loss or gain of electrons.
Easy
True or false?
44.Complete the sentence: All metals lose electrons to become positively charged ions.
Easy
All metals lose electrons to become ____ charged ions.
45.Complete the sentence about dot-and-cross diagrams.
Easy
In a dot-and-cross diagram, the charge on an ion is written at the top ____ corner.
46.State one reason why ionic compounds have high melting points.
Medium
47.How many electrons are transferred from one magnesium atom to oxygen atoms to form magnesium oxide (MgO)?
Easy
48.Complete the sentence about the formation of ionic bonds.
Easy
The force of attraction between oppositely charged ions is called an ____ bond.
49.State the formula of the ionic compound formed between aluminium and oxygen.
Easy
50.Explain why solid sodium chloride does not conduct electricity but molten sodium chloride does.
Medium
51.Explain why magnesium oxide has a higher melting point than sodium chloride.
Hard
52.How many electrons are transferred from one magnesium atom to oxygen atoms to form magnesium oxide (MgO)?
Medium
- A2
- B1
- C4
- D3

字卡

What is an ion?

An ion is an electrically charged atom or group of atoms formed by the loss or gain of electrons.

Why do atoms form ions?

Atoms form ions to obtain a full outer shell of electrons, like a noble gas.

What is a cation?

A cation is a positively charged ion formed when an atom loses electrons.

What is an anion?

An anion is a negatively charged ion formed when an atom gains electrons.

What type of elements form cations?

Metals lose electrons to form cations (positive ions).

What type of elements form anions?

Non-metals gain electrons to form anions (negative ions).

What is the charge on ions formed by Group 1 elements?

Group 1 elements form ions with a 1+ charge.

What is the charge on ions formed by Group 2 elements?

Group 2 elements form ions with a 2+ charge.

What is the charge on ions formed by Group 6 elements?

Group 6 elements form ions with a 2− charge.

What is the charge on ions formed by Group 7 elements?

Group 7 elements form ions with a 1− charge.

What is an ionic bond?

An ionic bond is the strong electrostatic force of attraction between oppositely charged ions.

Between which types of elements does ionic bonding occur?

Ionic bonding occurs between metal atoms and non-metal atoms.

What is a dot-and-cross diagram?

A dot-and-cross diagram shows the arrangement of outer-shell electrons in an ionic or covalent compound, using dots and crosses.

How is the charge shown in a dot-and-cross diagram for an ion?

The ion is enclosed in square brackets with the charge written at the top right-hand corner.

What is the formula of sodium chloride?

NaCl

Describe the lattice structure of ionic compounds.

Ionic compounds have a giant lattice structure with a regular arrangement of alternating positive and negative ions in 3D.

What is the overall charge of an ionic compound?

An ionic compound has no overall charge; positive and negative charges balance.

What are the typical physical properties of ionic compounds?

Ionic compounds are usually solid at room temperature, have high melting and boiling points, and conduct electricity when molten or in solution but not in solid state.

Why do ionic compounds have high melting points?

They have strong electrostatic forces between oppositely charged ions in a giant lattice, requiring lots of energy to overcome.

Why are ionic compounds poor conductors in the solid state?

In the solid state, ions are in fixed positions and cannot move to carry charge.

Why do ionic compounds conduct electricity when molten or dissolved?

When molten or dissolved, ions are free to move and carry charge.

Which has a higher melting point: NaCl or MgO? Why?

MgO has a higher melting point because Mg²⁺ and O²⁻ have greater charges than Na⁺ and Cl⁻, leading to stronger electrostatic forces.

Write the dot-and-cross diagram for NaCl (outer electrons only).

Na loses its outer electron to Cl; Na⁺ has no outer electrons (shown as [Na]⁺), Cl⁻ has 8 outer electrons (shown as [Cl]⁻ with 8 dots/crosses).

Write the dot-and-cross diagram for MgO.

Mg loses two outer electrons to O; Mg²⁺ has no outer electrons, O²⁻ has 8 outer electrons; formula MgO.

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