Ionic bonding (Edexcel IGCSE Chemistry (Modular): Unit 2): Flashcards

True.

Group 1 metals have one electron in their outer shell. They lose this electron to form ions with a 1+ charge, such as Na⁺.

Compound ions are ions made from more than one element, such as ammonium (NH₄⁺), hydroxide (OH^-), carbonate (CO₃^2-) and sulfate (SO₄^2-).

Group 7 non-metals form ions with a 1– charge. They gain one electron to fill their outer shell, becoming negatively charged anions (for example, Cl^-).

The hydroxide ion has the formula OH^- and a charge of 1–. The sulfate ion has the formula SO₄^2- and a charge of 2–.

True.

Ammonium (NH₄⁺) is a compound ion because it contains more than one element (nitrogen and hydrogen). It carries a positive charge of 1+.

The charges are:

1. Iron(II) — Fe²⁺ (2+ charge)

2. Iron(III) — Fe³⁺ (3+ charge)

3. Copper(II) — Cu²⁺ (2+ charge)

The swap-and-drop method is a technique for finding the formula of an ionic compound: the size of the charge on each ion becomes the subscript number for the other ion, giving the correct ratio.

Ionic compounds have no overall charge because the positive charges from the metal ions are exactly cancelled out by the negative charges from the non-metal ions. The total charge across the compound equals zero.

Ionic compounds have no overall charge because the positive and negative charges must cancel each other out.

False.

Copper(II) has a 2+ charge and chloride has a 1– charge. Using the swap-and-drop method, two chloride ions are needed to cancel the 2+ charge, so the correct formula is CuCl₂.

Write down the charges of both ions and check whether they cancel each other out. If the charges are equal and opposite, one of each ion is needed. If they are not equal, adjust the number of each ion until the total charge is zero.

When a compound ion such as hydroxide appears more than once in a formula, brackets must be placed around it.

True.

Iron(III) has a 3+ charge and chloride has a 1– charge. Three chloride ions are needed to cancel the 3+ charge, giving the formula FeCl₃.

Complete the table.

Brackets must be included when a compound ion (such as hydroxide or sulfate) is needed more than once in the formula. For example, magnesium hydroxide is written as Mg(OH)₂, not MgOH₂.

A dot-and-cross diagram shows the outer electrons of each atom using dots and crosses, the transfer of electrons between atoms, and each ion enclosed in square brackets with its charge shown outside.

In sodium chloride, the sodium atom loses one electron to the chlorine atom, forming a positive ion and a negative ion.

True.

Sodium is a Group 1 metal with one outer electron. It loses this electron to chlorine, forming a sodium ion with a 1+ charge (Na⁺).

The key rules are:

1. Show only the outer electrons, using dots and crosses to distinguish atoms

2. Enclose each ion in square brackets

3. Write the charge as a superscript outside the right-hand bracket

A dot-and-cross diagram is a diagram that uses dots and crosses to represent the outer electrons of atoms, showing how electrons are transferred or shared when chemical bonds form.

True.

Magnesium is a Group 2 metal with two outer electrons. It loses both electrons to oxygen, forming Mg²⁺. Oxygen gains these two electrons to form O^2-.

In magnesium oxide, two electrons are transferred from each magnesium atom to each oxygen atom.

The charge on the ion must be shown as a superscript on the outside of the right-hand bracket — for example, 1+ or 2– — to indicate whether the ion is positive or negative.

A giant ionic lattice is a regular three-dimensional arrangement of thousands of alternating positive and negative ions held together by strong electrostatic forces of attraction acting in all directions.

Ionic compounds have high melting and boiling points because they contain a giant ionic lattice with strong electrostatic forces of attraction between oppositely charged ions acting in all directions. A large amount of energy is needed to overcome these forces.

False.

In the solid state, ions are held in fixed positions in the lattice and cannot move. Because the ions cannot move, they cannot carry a charge and the compound cannot conduct electricity.

Ionic compounds cannot conduct electricity in the solid state because the ions are fixed and cannot move.

When an ionic compound is melted or dissolved in water, the ions are free to move. These moving ions can carry a charge through the liquid, allowing electricity to flow.

True.

Magnesium oxide contains Mg²⁺ and O^2- ions, which have a greater charge than the Na⁺ and Cl^- ions in sodium chloride. Greater ionic charges mean stronger electrostatic forces, requiring more energy to overcome.

Electrostatic forces of attraction are the strong forces between oppositely charged positive and negative ions in an ionic compound. They act in all directions and hold the giant ionic lattice together.

The greater the charge on the ions, the stronger the electrostatic forces between them. Stronger forces require more energy to overcome, so the melting point is higher.

Complete the table about electrical conductivity of ionic compounds.

For a substance to conduct electricity, there must be freely moving charged particles — either electrons or ions — that can carry a charge through the material.