The Ionic Model

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수업 노트

Forming Ions

Ionic bonds form by the transfer of electrons from a metallic element to a non-metallic element.
Metals lose electrons from their valence shell to form positively charged cations.
Non-metal atoms gain electrons to form negatively charged anions.
After electron transfer, ions usually have the same electronic configuration as a noble gas.
For example, Na⁺ has the configuration [2,8] like neon, and Cl⁻ has [2,8,8] like argon.
The group number of an element helps predict how many electrons it will lose or gain.

Formation of ions

Binary Ionic Compounds

A binary ionic compound is composed of ions of two different elements: a metal cation and a non-metal anion.
Ionic bonding is the force of attraction between oppositely charged species/ions.
The strong electrostatic attractions between cations and anions require a lot of energy to overcome, giving ionic compounds high melting points.
Binary ionic compounds are named with the cation first, followed by the anion with the suffix -ide (e.g. sodium iodide).
Ionic compounds are electrically neutral; the total positive charge equals the total negative charge.

Charges on Ions

Group 1, 2 and 13 metals form ions with charges of +1, +2 and +3 respectively.
Transition elements can form ions with variable charges, shown by Roman numerals in names (Stock notation), e.g. copper(II) oxide has Cu²⁺.
Non-metals in Group 17 gain 1 electron and have a 1− charge, e.g. Br⁻.
Non-metals in Group 16 gain 2 electrons and have a 2− charge, e.g. O²⁻.
Non-metals in Group 15 gain 3 electrons and have a 3− charge, e.g. N³⁻.
Some non-metals form positive ions, such as ammonium, NH₄⁺, and hydrogen, H⁺.

Polyatomic Ions

Polyatomic ions are ions made up of more than one type of atom, also called compound negative ions.
The seven polyatomic ions you need to know are: ammonium NH₄⁺, hydroxide OH⁻, nitrate NO₃⁻, hydrogencarbonate HCO₃⁻, carbonate CO₃²⁻, sulfate SO₄²⁻, and phosphate PO₄³⁻.
When more than one polyatomic ion is needed in a formula, it is placed in brackets with the number outside, e.g. Ca(NO₃)₂.
To determine a formula, balance the positive and negative charges so they cancel out.

Ionic Lattices

An ionic lattice is a crystalline structure formed by ions in a regular, repeating pattern.
The lattice consists of alternating cations and anions, arranged so that positive and negative charges cancel out, making the lattice overall electrically neutral.
Ionic compounds are represented using empirical formulas, which show the simplest whole-number ratio of ions.
The strong electrostatic forces of attraction between oppositely charged ions act in all directions and hold the lattice together.

The lattice structure of sodium chloride

Lattice Enthalpy

Lattice dissociation enthalpy (ΔH_latt) is the standard enthalpy change when 1 mole of gaseous ions is formed from the solid lattice.
Lattice enthalpy is always endothermic (positive value) because energy is required to break the bonds between ions in the lattice.
For example: NaCl(s) → Na⁺(g) + Cl⁻(g), ΔH_latt = +790 kJ mol⁻¹.
Lattice enthalpy increases as ionic charge increases and ionic radius decreases, due to stronger electrostatic attractions.

Properties of Ionic Compounds

Ionic compounds are hard and brittle; crystals shatter when layers shift and like charges align.
They have high melting and boiling points because strong electrostatic forces act in all directions and keep ions strongly together.
Melting and boiling points increase with the charge density of the ions; for example, MgO has a higher melting point than NaCl.
Ionic compounds are not volatile as large amounts of energy are needed to overcome the strong electrostatic forces.
They are generally soluble in water because polar water molecules form ion–dipole interactions and hydrate the ions.
Lower solvent polarity and weaker ion–solvent interactions reduce solubility.

Electrical conductivity of ionic compounds

Electrical Conductivity of Ionic Compounds

Ionic compounds only conduct electricity when molten or in solution, because the ions are free to move.
As a solid, the ions are in fixed positions and cannot move, so they do not conduct electricity.
When molten or aqueous, the ions can freely move around and carry charge.

Comparing Structure Types

Giant ionic: high melting/boiling points, conduct only when molten or in solution, generally soluble, hard and brittle, solid at room temperature, particles are ions.
Giant metallic: moderately high to high melting/boiling points, conduct when solid or liquid, insoluble, hard and malleable, solid at room temperature, particles are positive ions in a sea of electrons.
Simple covalent: low melting/boiling points, do not conduct electricity, usually insoluble unless polar, soft, solid/liquid/gas at room temperature, particles are small molecules.
Giant covalent: very high melting/boiling points, do not conduct electricity (except graphite), insoluble, very hard (diamond/silica) or soft (graphite), solid at room temperature, particles are atoms.

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연습 문제

무료 미리 보기 — 60개 중 8개 문제. 가입하면 전부 볼 수 있어요.

1.Which statement best describes ionic bonding?
Easy
- AThe electrostatic attraction between oppositely charged ions
- BThe electrostatic attraction between cations and delocalised electrons
- CThe electrostatic attraction of nuclei towards shared electrons
- DThe electrostatic attraction between nuclei
2.What is the correct formula for ammonium carbonate?
Easy
- A(NH₄)₂CO₃
- BNH₄CO₃
- C(NH₄)₃CO₃
- DNH₄(CO₃)₂
3.Which crystal structure does not conduct electricity when solid, has a high melting point and can conduct electricity when molten?
Medium
- AGiant ionic
- BGiant metallic
- CCovalent network
- DSimple molecular
4.Which of the following compounds is not bonded ionically?
Easy
- ACH₃OH
- BCaCO₃
- CNaOH
- DBaCl₂
5.Magnesium oxide has a very high melting temperature. Which of the following is the best description of its structure and bonding?
Easy
- AGiant ionic
- BGiant metallic
- CNetwork covalent
- DSimple molecular
6.Which of the following compounds has both covalent and ionic bonds?
Medium
- Apotassium carbonate, K₂CO₃
- Bcalcium bromide, CaBr₂
- Cpropanoic acid, CH₃CH₂COOH
- Ddichloromethane, CH₂Cl₂
7.Potassium bromide is an ionic compound. When can potassium bromide conduct electricity?
Medium
- AMolten and aqueous only
- BSolid and molten only
- CSolid and aqueous only
- DAqueous only
8.Which of the following substances has the highest melting point?
Hard
- AMgO
- BNa₂O
- CO₂
- DC (graphite)

더 많은 문제

9.Of the four compounds listed below, which one has the greatest ionic character?
Hard
- ACaO
- BHCl
- CMgS
- DCO₂
10.What is the correct formula for aluminium sulfate?
Medium
- AAl₂(SO₄)₃
- BAl₃(SO₄)₂
- CAl(SO₄)₂
- DAlSO₄
11.Which of the following statements about ions and ionic compounds are true? (select all that apply)
Medium
- ANitrogen can form a 3− ion
- BPotassium can form a cation
- CThe formula for aluminium chloride is AlCl₂
- DMagnesium can form a 2+ ion
- EChlorine can form a 2− ion
12.Lattice enthalpy is always endothermic because energy is required to break the bonds between the ions in the lattice.
Easy
True or false?
13.A sodium ion has the same electronic configuration as an argon atom.
Easy
True or false?
14.Match each polyatomic ion to its correct formula and charge.
Medium
- Ammonium
- Hydroxide
- Nitrate
- Sulfate
- Phosphate
- NH₄⁺
- OH⁻
- NO₃⁻
- SO₄²⁻
- PO₄³⁻
15.Place the following ionic compounds in order of increasing melting point, from lowest to highest.
Medium
- NaCl
- MgO
- KCl
16.An ionic compound has the empirical formula H₄N₂O₃. Which pair of ions is present in this compound?
Medium
- ANH₄⁺ and NO₃⁻
- BNH₄⁺ and NO₂⁻
- CNH₄⁺ and N³⁻
- DH⁺ and NO₃⁻
17.Aluminium iodide vapour can exist as an AlI₃ molecule. How many valence electrons are in one AlI₃ molecule?
Medium
- A24
- B26
- C22
- D28
18.What are the correct formulas for the phosphate, ammonium, ethanoate and nitrate ions?
Medium
- APO₄³⁻, NH₄⁺, CH₃COO⁻, NO₃⁻
- BPO₃²⁻, NH₄⁻, CH₃COO⁻, NO₂⁻
- CPO₄²⁻, NH₄⁺, CH₃CH₂COO⁻, NO₃⁻
19.Which physical property of an ionic compound is correctly described?
Medium
- AIonic crystals are hard and brittle because the layers shatter when like charges align
- BIonic compounds are volatile because the ions escape easily
- CIonic compounds conduct electricity when solid because ions are mobile
- DIonic compounds are generally insoluble in water
20.Which of the following statements about ionic lattices and lattice enthalpy are correct? (select all that apply)
Hard
- ALattice enthalpy increases as ionic charge increases
- BLattice enthalpy increases as ionic radius decreases
- CLattice enthalpy is always negative because the lattice forms spontaneously
- DThe lattice is overall electrically neutral
- EIonic compounds are represented by molecular formulas showing all ions
21.Ionic compounds are generally soluble in water because polar water molecules form ion–dipole interactions with the ions.
Easy
True or false?
22.Ionic compounds conduct electricity in the solid state because the ions can move within the lattice.
Easy
True or false?
23.Match each structure type to its electrical conductivity behaviour.
Medium
- Giant ionic
- Giant metallic
- Simple covalent
- Giant covalent (except graphite)
- Only when molten or in solution
- When solid or liquid
- Do not conduct electricity
- Do not conduct electricity (except graphite)
24.Arrange the following ionic compounds in order of increasing lattice enthalpy, from lowest to highest.
Medium
- NaCl
- MgO
- KCl
25.Which of the following is the correct name for the compound formed between copper with a 2+ charge and oxygen?
Medium
- Acopper(II) oxide
- Bcopper(I) oxide
- Ccopper oxide(II)
- Dcopper dioxide
26.Metals lose electrons from their valence shell to form positively charged cations.
Easy
True or false?
27.Which of the following are properties of giant ionic lattice structures? (select all that apply)
Medium
- AHigh melting and boiling points
- BHard and brittle
- CConduct electricity when solid
- DGenerally soluble in water
- ELow volatility
28.Place the following ionic compounds in order of increasing lattice enthalpy, from lowest to highest.
Medium
- NaCl
- KCl
- MgO
- CaO
29.Which statement about the formation of ions is correct?
Medium
- AMetals gain electrons to form anions.
- BNon-metals lose electrons to form cations.
- CMetals lose electrons from their valence shell to form cations.
- DNon-metals gain protons to form anions.
30.An ionic compound has the empirical formula H4N2O3. Which pair of ions is present in this compound?
Medium
- ANH4+ and NO3-
- BNH4+ and NO2-
- CNH2+ and NO3-
- DNH4+ and CO3²-
31.Aluminium iodide vapour can exist as an AlI3 molecule. How many valence electrons are in one AlI3 molecule?
Hard
- A22
- B24
- C26
- D28
32.A student is given four unknown solids and records the following results. Which solid is most likely to be a giant ionic lattice?
Medium
- ASolid W: melting point 95 °C, does not conduct when solid or molten, insoluble in water
- BSolid X: melting point 839 °C, conducts when molten but not when solid, soluble in water
- CSolid Y: melting point 1389 °C, conducts when solid and molten, insoluble in water
- DSolid Z: melting point 3550 °C, does not conduct when solid or molten, insoluble in water
33.The lattice dissociation enthalpy of NaCl is +790 kJ mol⁻¹. What is the enthalpy change when 3.0 moles of NaCl are completely broken down into gaseous ions?
Medium
- A+2370 kJ
- B+790 kJ
- C+263 kJ
- D+1580 kJ
34.A compound has the empirical formula H₄N₂O₃. Which pair of ions is present in this compound?
Hard
- ANH₄⁺ and NO₃⁻
- BNH₄⁺ and NO₂⁻
- CNH₃⁺ and NO₃⁻
- DNH₄⁺ and CO₃²⁻
35.The lattice dissociation enthalpies of three compounds are: MgO +3795 kJ mol⁻¹, Na₂O +2481 kJ mol⁻¹, K₂O +2230 kJ mol⁻¹. Which statement best explains the trend?
Hard
- ALattice enthalpy increases as ionic charge increases and ionic radius decreases.
- BLattice enthalpy increases as ionic charge decreases and ionic radius increases.
- CLattice enthalpy depends only on the mass of the ions.
- DLattice enthalpy is higher when the ions are larger and less charged.
36.Which of the following statements about ionic lattices are correct? (select all that apply)
Medium
- AThey are held together by strong electrostatic forces of attraction between oppositely charged ions.
- BThey are electrically neutral overall.
- CThey conduct electricity when solid because ions are free to move.
- DThey have high melting points because the electrostatic forces act in all directions.
- EThey are represented by empirical formulas showing the simplest whole-number ratio of ions.
37.A student heats a white crystalline solid. It melts at 1074 K. The molten liquid conducts electricity, but the solid does not. The solid is soluble in water, and the aqueous solution also conducts electricity. What is the most likely structure of the solid?
Medium
- AGiant ionic lattice
- BGiant metallic lattice
- CSimple molecular
- DGiant covalent network
38.Which of the following statements about the electrical conductivity of ionic compounds are correct? (select all that apply)
Medium
- ASolid ionic compounds do not conduct electricity because their ions are fixed in position.
- BMolten ionic compounds conduct electricity because their ions are free to move.
- CAqueous solutions of ionic compounds conduct electricity because the ions are mobile.
- DAll ionic compounds conduct electricity in the solid state.
- EIonic compounds conduct electricity by the movement of delocalised electrons.
39.Lattice dissociation enthalpy is defined as the enthalpy change when one mole of a solid ionic lattice is formed from its gaseous ions.
Easy
True or false?
40.Match each observation with the correct conclusion about the type of structure or bonding.
Medium
- Solid does not conduct electricity, molten solid conducts electricity
- Solid conducts electricity
- Solid is soft and melts at 95 °C
- Solid is very hard and does not conduct electricity
- Giant ionic lattice
- Giant metallic lattice
- Simple molecular structure
- Giant covalent network
41.Complete the names of the binary ionic compounds formed from the following pairs of elements.
Easy
Lithium and sulfur form ____. Calcium and nitrogen form ____. Sodium and hydrogen form ____.
42.The lattice dissociation enthalpy of NaCl is +790 kJ mol⁻¹. How much energy, in kJ, is required to completely break down 2 moles of NaCl into gaseous ions?
Medium
43.State the term for an ion made up of more than one type of atom, such as the ammonium ion.
Medium
44.Complete the definition of ionic bonding.
Easy
Ionic bonding is the ____ of attraction between ____ charged species or ions.
45.Complete the sentences about the properties of ionic compounds.
Medium
Ionic compounds have ____ melting points because the electrostatic forces between the ions act in all directions. They are ____ in water because polar water molecules form ion–dipole interactions.
46.In the reaction NaCl(s) → Na⁺(g) + Cl⁻(g), the enthalpy change is +790 kJ mol⁻¹. Calculate the enthalpy change, in kJ, when 0.5 moles of NaCl are converted into gaseous ions.
Hard
47.Give the name of the binary ionic compound formed when calcium reacts with nitrogen.
Medium
48.State the noble gas that has the same electronic structure as the Mg²⁺ ion.
Medium
49.Complete the definition of lattice enthalpy.
Medium
Lattice dissociation enthalpy is the standard enthalpy change when 1 mole of gaseous ____ is formed from the solid ____.
50.Complete the naming rules for binary ionic compounds.
Medium
Binary ionic compounds are named with the ____ first, followed by the anion, which adopts the suffix ____.
51.State the type of bonding in potassium chloride, which melts at 1043 K.
Easy
52.The lattice dissociation enthalpy of NaCl is +790 kJ mol⁻¹. Calculate the energy, in kJ, required to break down 2.5 moles of NaCl into gaseous ions.
Medium
53.Define ionic bonding.
Medium
54.Describe the structure and bonding in solid magnesium oxide.
Medium
55.Explain why solid magnesium chloride does not conduct electricity, but molten magnesium chloride does.
Hard
56.Explain why lattice enthalpy is always endothermic.
Hard
57.Lithium bromide dissolves in organic solvents, whereas potassium fluoride is insoluble in organic solvents. Suggest a reason for the difference in solubility.
Hard
58.The lattice dissociation enthalpy of NaCl is +790 kJ mol⁻¹. How much energy, in kJ, is required to completely break down 2 moles of NaCl into gaseous ions?
Medium
- A1896 kJ
- B1580 kJ
- C1738 kJ
- D1422 kJ
59.In the reaction NaCl(s) → Na⁺(g) + Cl⁻(g), the enthalpy change is +790 kJ mol⁻¹. Calculate the enthalpy change, in kJ, when 0.5 moles of NaCl are converted into gaseous ions.
Hard
- A475 kJ
- B435 kJ
- C395 kJ
- D355 kJ
60.The lattice dissociation enthalpy of NaCl is +790 kJ mol⁻¹. Calculate the energy, in kJ, required to break down 2.5 moles of NaCl into gaseous ions.
Medium
- A2173 kJ
- B1777 kJ
- C2371 kJ
- D1975 kJ

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