Group 7: the halogens

The elements in Group 7 of the periodic table are known as the halogens.

Figure 4 shows information about some of the elements in Group 7.

Predict the boiling point of chlorine.

Use Figure 4.

What is the state of fluorine at –250 °C?

Use Figure 4.

Astatine (At) is an element in Group 7.

What is the number of electrons in the outer shell of an astatine atom?

Hydrogen reacts with astatine to produce hydrogen astatide.

Predict the formula of hydrogen astatide.

Explain the trend in reactivity of the elements going down Group 7.

A more reactive halogen can displace a less reactive halogen from a solution of its salt.

Write a balanced equation for the reaction between bromine and potassium iodide.

This question is about the periodic table.

Sodium and potassium are in Group 1 of the periodic table.

Give one similarity and one difference between the electronic structures of sodium and potassium.

Group 1 elements react with water.

Give two observations made when potassium reacts with water.

Potassium hydroxide solution is produced when potassium reacts with water.

What is the colour of universal indicator when added to potassium hydroxide solution?

Give one reason for your answer.

Colour of universal indicator

Table 4 shows the densities of some of the elements in Group 0 of the periodic table.

Plot the data from Table 4 on Figure 15.

Estimate the density (X) of krypton.

Use Figure 15 and Table 4.

The elements in Group 7 are called the halogens.

A more reactive halogen can displace a less reactive halogen from a solution of its salt.

Which combination of solutions will produce a reaction when mixed?

Tick () one box.

Which of the following describes the trends going down Group 7?

Tick () one box.

This question is about the periodic table.

Sodium and potassium are in Group 1 of the periodic table.

Give one similarity and one difference between the electronic structures of sodium and potassium.

Group 1 elements react with water.

Give two observations made when potassium reacts with water.

Potassium hydroxide solution is produced when potassium reacts with water.

What is the colour of universal indicator when added to potassium hydroxide solution?

Give one reason for your answer.

Colour of universal indicator

Table 1 shows the densities of some of the elements in Group 0 of the periodic table.

Plot the data from Table 1 on Figure 1.

Estimate the density (X) of krypton.

Use Figure 1 and Table 1.

The elements in Group 7 are called the halogens.

A more reactive halogen can displace a less reactive halogen from a solution of its salt.

Which combination of solutions will produce a reaction when mixed?

Tick () one box.

Which of the following describes the trends going down Group 7?

Tick () one box.

This question is about the periodic table.

Figure 6 shows an early version of the periodic table published by a scientist.

The scientist left gaps in the periodic table in Figure 6.

Each gap is represented by a question mark (?).

Give one reason why the scientist left gaps in this periodic table.

Which scientist published the periodic table in Figure 6 ?

Tick (✓) one box.

The modern periodic table is different from the periodic table in Figure 6.

One extra group of elements has been added.

What is the name of the extra group of elements in the modern periodic table?

Tick (✓) one box.

Why do the elements in Group 1 of the modern periodic table have similar chemical properties?

Tick (✓) one box.

Table 3 shows the melting points of the first five elements going down Group 1.

Predict value X.

Give one observation you would see when a small piece of potassium is added to water.

Table 4 shows information about the first five elements going down Group 7.

Complete Table 4.

The elements in Group 7 consist of molecules.

What is the formula of a molecule of bromine?

Tick (✓) one box.

This question is about the elements in Group 7 of the periodic table. Table 1 shows the melting points and boiling points of some of the elements.

What is the state of bromine at 100 °C? Use Table 1. Tick (✓) one box.

What temperature does chlorine gas condense at to form a liquid? Use Table 1.

Complete the sentences.

This is because the size of the molecules increases so the

A teacher investigated the reaction of iron with chlorine. Figure 1 shows the apparatus used.

Why did the teacher do the investigation in a fume cupboard? Tick (✓) one box.

The word equation for the reaction is: iron + chlorine → iron chloride Iron chloride is a solid. The teacher weighed the glass tube and contents:

• before the reaction

• after the reaction.

What happened to the mass of the glass tube and contents during the reaction? Give one reason for your answer.

The mass of the glass tube and contents.

The teacher repeated the investigation with bromine gas and with iodine gas. Table 2 shows the results.

Fluorine is above chlorine in Group 7. Predict what you would observe when fluorine gas reacts with iron. Use Table 2.

Balance the equation for the reaction between iron and bromine.

2 Fe + _____ Br 2 → 2 FeBr 3

Calculate the relative formula mass (M_r) of FeBr₃ Relative atomic masses (A_r): Fe = 56 Br = 80

This question is about the halogens. Table 5 shows the melting points and boiling points of some halogens.

What is the state of bromine at 0 °C and at 100 °C? Tick (✓) one box. State at 0 °C State at 100 °C

Explain the trend in boiling points of the halogens shown in Table 5.

Why is it not correct to say that the boiling point of a single bromine molecule is 59 °C?

Iron reacts with each of the halogens in their gaseous form. Figure 5 shows the apparatus used.

Give one reason why this experiment should be done in a fume cupboard.

Explain why the reactivity of the halogens decreases going down the group.

A teacher investigated the reaction of iron with chlorine using the apparatus in Figure 5. The word equation for the reaction is: iron + chlorine → iron chloride The teacher weighed:

• the glass tube

• the glass tube and iron before the reaction

• the glass tube and iron chloride after the reaction.

Table 6 shows the teacher’s results.

Calculate the simplest whole number ratio of: moles of iron atoms moles of chlorine atoms Determine the balanced equation for the reaction. Relative atomic masses (A_r): Cl = 35.5 Fe = 56

Equation for the reaction

This question is about the periodic table. In the 19th century, some scientists tried to classify the elements by arranging them in order of their atomic weights. Figure 11 shows the periodic table Mendeleev produced in 1869. His periodic table was more widely accepted than previous versions.

The atomic weight of tellurium (Te) is 128 and that of iodine (I) is 127 Why did Mendeleev reverse the order of these two elements?

Mendeleev left spaces marked with an asterisk * He left these spaces because he thought missing elements belonged there. Why did Mendeleev’s periodic table become more widely accepted than previous versions?

Mendeleev arranged the elements in order of their atomic weight. What is the modern name for atomic weight?

Tick (✓) one box.

Complete the sentence. In the modern periodic table, the elements are arranged in order of

Chlorine, iodine and astatine are in Group 7 of the modern periodic table.

Astatine (At) is below iodine in Group 7. Predict:

• the formula of an astatine molecule

• the state of astatine at room temperature.

Formula of astatine molecule State at room temperature

Sodium is in Group 1 of the modern periodic table. Describe what you would see when sodium reacts with chlorine.

This question is about the periodic table. In the 19th century, some scientists tried to classify the elements by arranging them in order of their atomic weights. Figure 1 shows the periodic table Mendeleev produced in 1869. His periodic table was more widely accepted than previous versions.

The atomic weight of tellurium (Te) is 128 and that of iodine (I) is 127 Why did Mendeleev reverse the order of these two elements?

Mendeleev left spaces marked with an asterisk * He left these spaces because he thought missing elements belonged there. Why did Mendeleev’s periodic table become more widely accepted than previous versions?

Mendeleev arranged the elements in order of their atomic weight. What is the modern name for atomic weight?

Tick (✓) one box.

Complete the sentence. In the modern periodic table, the elements are arranged in order of

Chlorine, iodine and astatine are in Group 7 of the modern periodic table.

Astatine (At) is below iodine in Group 7. Predict:

• the formula of an astatine molecule

• the state of astatine at room temperature.

Formula of astatine molecule State at room temperature

Sodium is in Group 1 of the modern periodic table. Describe what you would see when sodium reacts with chlorine.

The halogens are elements in Group 7.

Bromine is in Group 7.

Give the number of electrons in the outer shell of a bromine atom.

Bromine reacts with hydrogen. The gas hydrogen bromide is produced.

What is the structure of hydrogen bromide?

Tick one box.

What is the formula for fluorine gas?

Tick one box.

A student mixes solutions of halogens with solutions of their salts.

Table 1 shows the student’s observations.

Explain how the reactivity of the halogens changes going down Group 7.

Use the results in Table 1.

A company uses chlorine to produce titanium chloride from titanium dioxide.

What is the relative formula mass (M_r) of titanium dioxide, TiO₂ ?

Relative atomic masses (A_r): O = 16 Ti = 48

Tick one box.

The company calculates that 500 g of titanium dioxide should produce 1.2 kg of titanium chloride.

However, the company finds that 500 g of titanium dioxide only produces 900 g of titanium chloride.

Calculate the percentage yield.

This question is about Group 7 elements. Chlorine is more reactive than iodine.

Name the products formed when chlorine solution reacts with potassium iodide solution.

Explain why chlorine is more reactive than iodine.

Chlorine reacts with hydrogen to form hydrogen chloride. Explain why hydrogen chloride is a gas at room temperature. Answer in terms of structure and bonding.

Bromine reacts with methane in sunlight. Figure 9 shows the displayed formulae for the reaction of bromine with methane.

Table 3 shows the bond energies and the overall energy change in the reaction.

Calculate the bond energy X for the C^___Br bond. Use Figure 9 and Table 3.