8.2 Group Properties & Trends

Scandium, proton number 21, is not a typical transition element.

Scandium is a low density metal which has only one oxidation state in its compounds. Scandium compounds are white solids which form colourless solutions. Titanium, the next metal in the period, is a far more typical transition element. 

How would the properties of titanium differ from those of scandium?

Scandium fluoride is an ionic compound. The valency of scandium in scandium fluoride is three.

Draw a diagram which shows the formula of this compound, the charges on the ions and the arrangement of the valency electrons around the negative ions.

Use × to represent an electron from a fluorine atom.
Use ○ to represent an electron from a scandium atom.

Scandium oxide is insoluble in water. Describe how you could show that it is an amphoteric oxide.

For each of the following, select an element from Period 4, potassium to krypton, which matches the description.

A metal that reacts rapidly with cold water to form a compound of the type M(OH)₂ and hydrogen.

Its only oxidation state is 0.

It has a macromolecular oxide, XO₂, which has similar physical properties to those of diamond.

This is one of the metals alloyed with iron in stainless steel.

It can be reduced to an ion of the type X^–.

It can form a covalent hydride having the formula H₂X.

Its soluble salts are blue and its oxide is black.

It is a liquid at room temperature.

This question is concerned with the elements in Period 5, Rb to Xe.

The electron distributions of some of these elements are given in the following list.

[1]

[1]

[1]

Predict two differences in physical properties and two differences in chemical properties between rubidium and the transition metal niobium.

Three of the halogens in Group VII are:

chlorine
bromine
iodine

Describe how you could distinguish between aqueous potassium bromide and aqueous potassium iodide.

Test ....................

Result with bromide ............................................................

Result with iodide ............................................................

0.015 moles of iodine react with 0.045 moles of chlorine to form 0.030 moles of a single product.

Complete the equation.

I₂ + ............ Cl₂ → ................................

Traces of chlorine can be separated from bromine vapour by diffusion.

Which gas would diffuse the faster and why?

Rubidium and strontium are very reactive metals at the top of the reactivity series. Because their ions have different charges, their compounds behave differently when heated.

The formulae of the ions of these two elements are Rb⁺ and Sr²⁺.

Explain why these metals, which are in different groups, form ions which have different charges.

Strontium carbonate is similar to calcium carbonate. It is insoluble in water and it decomposes when heated. Rubidium carbonate is soluble in water and does not decompose when heated.

Extended Only

Use your copy of the periodic table to help you answer these questions.

Predict the formula of each of the following compounds.

Give the formula of the following ions.

Draw a diagram showing the arrangement of the valency electrons in one molecule of the covalent compound nitrogen trichloride.

Use x to represent an electron from a nitrogen atom.
Use o to represent an electron from a chlorine atom.

Potassium and vanadium are elements in Period IV.

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Fluorine and astatine are halogens. Use your knowledge of the other halogens to predict the following:

[2]

Separate: Chemistry Only

For each of the following, give the name of an element from Period 2 (lithium to neon), which matches the description.
Elements may be used once, more than once or not at all.

[1]

[1]

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[1]

[1]

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Give the formula of a compound that contains

[1]

[1]

Choose an element from the list below which best fits the description.

An element which reacts with cold water.

It is a solid at room temperature and exists as diatomic molecules, X₂.

Separate: Chemistry and Extended Only

It can form two oxides, XO and X₂O₃.

This element has a hydride of the type XH₃.

Separate: Chemistry and Extended Only

It has a macromolecular structure similar to that of carbon.

Use your copy of the Periodic Table to answer these questions.

Choose an element from the Periodic Table to match each description.
You may give either the name or the symbol.

[1]

[1]

[1]

[1]

[1]

Predict the formula of each of the following compounds.

Give the formula of each of the following ions.

For each of the following select an element from Period 4, potassium to krypton, that matches the description.

It is a brown liquid at room temperature.

It forms a compound with hydrogen having the formula XH₄.

A metal that reacts violently with cold water.

It has a complete outer energy level.

Separate: Chemistry and Extended Only

It has oxidation states of 2 and 3 only.

It can form an ion of the type X^-.

Separate: Chemistry and Extended Only

One of its oxides is the catalyst in the Contact Process.

For each of the following, give the name of an element from Period 3 (sodium to argon), which matches the description.

An element which is gaseous at room temperature and pressure

An element that is added to water to kill bacteria.

An element that forms a basic oxide of the type XO.

Extended Only

An element that forms an amphoteric oxide.

An element that reacts vigorously with cold water to produce hydrogen.

Table 1 shows some properties of some of the halogens.

                                                                  Table 1Use the information in Table 1 to suggest:

• the colour of astatine ______________
• the boiling point of bromine ____________
• the state of iodine at 190 °C _______________

Aqueous chlorine reacts with aqueous potassium bromide as shown.

                                              Cl₂ + 2KBr → Br₂ + 2KCl

Name the salt formed in this reaction.

Explain why aqueous bromine does not react with aqueous potassium chloride.

Complete the dot-and-cross diagram in Figure 1 of a molecule of chlorine.
Show outer shell electrons only.

Figure 1

The diagram shows part of the structures of sodium bromide and sulfur.

Describe both sodium bromide and sulfur in terms of:

bonding

electrical conductivity

solubility in water

Sulfur is an element.

What is meant by the term element?

A coloured crystal of cobalt(II) chloride is placed at the bottom of a beaker containing water.
Colour spreads throughout the water over time. Figure 1 shows the spread of colour after two days.

Figure 1

Cobalt is a transition element. Lithium is a Group I element.

Describe two ways in which the properties of cobalt differ from those of lithium.

The properties of the first four Group I elements are shown in the table.

Answer these questions using only the information in the table.

Describe the general trend in the boiling points of the Group I elements.

Explain why it is difficult to predict the density of rubidium.

Deduce the state of rubidium at 45 °C. Explain your answer.