"IUPAC nomenclature: elements, monatomic ions and binary compounds"

The iron in a bridge ($\text{Fe}$) and the carbon dioxide we release when breathing ($\text{CO}_2$): one of the two is a simple substance and the other is a compound. The figure shows their particle models.

Which is which? Explain the difference between the two.

Oxygen ($\text{O}_2$), nitrogen ($\text{N}_2$), iron ($\text{Fe}$) and helium ($\text{He}$) are simple substances. Look at their formulas and state which of them form molecules, which are made up of individual atoms and whether any of them fits neither case.

When a sodium atom loses an electron, it becomes $\text{Na}^+$. The figure shows the process.

1. a) Explain what an ion is.
2. b) Does $\text{Na}^+$ have a positive or a negative charge?
3. c) What is this ion called?

Name these three monatomic ions: $\text{Cl}^-$, $\text{Ca}^{2+}$ and $\text{O}^{2-}$. Hint: positive ions keep the name of the atom (for example, the $\text{Na}^+$ ion is called sodium ion) and negative ions end in -ide (for example, the $\text{S}^{2-}$ ion is called sulfide ion).

In your bones, calcium is present as $\text{Ca}^{2+}$.

1. a) What does that $2+$ mean?
2. b) How many electrons has the calcium atom lost?
3. c) What is this ion called?

Magnesium is in group $2$ of the periodic table, just like calcium, and chlorine is in group $17$, just like fluorine.

1. a) Predict which ion magnesium will form and which chlorine will form.
2. b) Write the formula of magnesium chloride.
3. c) Explain where you obtained the charges you used.

Many fire extinguishers are filled with $\text{CO}_2$ gas. Naming it with Greek prefixes (mono-, di-, tri-) according to the number of oxygen atoms it has, what is the name of this gas?

Using the prefixes mono-, di- and tri-, write the formula for these two substances: carbon monoxide and carbon dioxide. What is the difference between the two molecules?

When a metal combines with a non-metal, the compound is named by placing the name of the metal first and then the non-metal with the ending -ide. Apply the rule and name table salt, $\text{NaCl}$, as well as the compound $\text{CaS}$.

Compounds of oxygen with another element are called oxides and are named "[element] oxide". Milk of magnesia from pharmacies contains $\text{MgO}$: name it. Also name the compound $\text{Na}_2\text{O}$.

When hydrogen combines with a metal, the compound is called a hydride. Name these two compounds: $\text{NaH}$ and $\text{CaH}_2$.

Match each formula to its correct name:

1. a) $\text{Na}_2\text{O}$
2. b) $\text{CO}_2$
3. c) $\text{FeS}$
4. d) $\text{CaF}_2$

1) iron(II) sulfide

2) carbon dioxide

3) calcium fluoride

4) sodium oxide

Classify each substance as a simple substance, oxide, hydride or binary salt, and write its name:

1. a) $\text{O}_2$
2. b) $\text{Na}_2\text{O}$
3. c) $\text{CaH}_2$
4. d) $\text{FeS}$
5. e) $\text{N}_2$
6. f) $\text{MgO}$

The reddish oxide that appears on an old bicycle is $\text{Fe}_2\text{O}_3$, and in it iron has a valency of $3$. Name it in both ways: using the prefixes mono-, di-, tri- and using the valency of iron written in brackets in Roman numerals.

Troilite, a mineral found in many meteorites, has the formula $\text{FeS}$, and in it iron has a valency of $2$.

1. a) Name it using Stock nomenclature (the valency in brackets and in Roman numerals).
2. b) Also name it using prefixes.

Iron can form two different ions: $\text{Fe}^{2+}$ and $\text{Fe}^{3+}$.

1. a) Write the formula of iron(II) oxide, formed by $\text{Fe}^{2+}$ and $\text{O}^{2-}$.
2. b) Write the formula of iron(III) oxide.
3. c) Name both oxides using prefixes.

In her exam, Amina wrote these names. Correct each one and explain the mistake she made:

1. a) $\text{NaCl}$: "sodium chlorine"
2. b) $\text{Fe}_2\text{O}_3$: "iron(II) oxide"
3. c) $\text{CO}_2$: "carbon monoxide"

Fluorite, a colourful mineral, is $\text{CaF}_2$.

1. a) Name this compound (remember the ending -ide).
2. b) Now in reverse: write the formula of sodium sulfide, which has two sodium atoms for every sulfur atom.

Common salt is made up of $\text{Na}^+$ ions and $\text{Cl}^-$ ions arranged in a lattice. The figure shows a section of that lattice.

1. a) Explain why the same number of ions of each type is needed for the salt to be neutral.
2. b) Write the formula of the salt and reason why it cannot be $\text{Na}_2\text{Cl}$.

Aluminium always forms the $\text{Al}^{3+}$ ion and oxygen forms the $\text{O}^{2-}$ ion.

1. a) Work out how many ions of each type are needed for the total charge of aluminium oxide to be zero.
2. b) Write the formula of aluminium oxide.

Calcium forms the $\text{Ca}^{2+}$ ion and fluorine forms the $\text{F}^-$ ion.

1. a) Reason how many fluoride ions are needed for each calcium ion for the total charge to be zero.
2. b) Write the formula of calcium fluoride.
3. c) Also name it using prefixes.

In nature, the salts $\text{NaCl}$ and $\text{CaCl}_2$ exist, but a $\text{NaCl}_2$ salt has never been found. Use the charges of the ions $\text{Na}^+$, $\text{Ca}^{2+}$ and $\text{Cl}^-$ to justify why the formula $\text{NaCl}_2$ is impossible and the other two can exist.

The prefixes mono-, di-, tri- indicate how many atoms of each element are in the formula.

1. a) Write the formula of dialuminium trioxide.
2. b) Write the formula of carbon monoxide.
3. c) Dialuminium trioxide is also called, simply, aluminium oxide. Knowing that aluminium only forms the $\text{Al}^{3+}$ ion, reason why in this case the prefixes can be omitted without causing confusion.

In the storeroom of a cleaning products factory there are three jars labelled as $\text{NaF}$, $\text{CaCl}_2$ and "zinc oxide".

1. a) Name the compounds $\text{NaF}$ and $\text{CaCl}_2$.
2. b) Write the formula of zinc oxide knowing that zinc forms the $\text{Zn}^{2+}$ ion and oxygen the $\text{O}^{2-}$ ion.
3. c) Justify using the charges of the ions why that oxide cannot have the formula $\text{Zn}_2\text{O}$.

Unit challenge. How much chemistry is hidden in the food in your kitchen? Become a chemical auditor and write a scientific report analysing the substances in your pantry.

1. Chemical exploration: Identify three real substances on labels: an element/simple substance (e.g., $O_2$ in packaging), a monatomic ion (e.g., $F^-$ or $Na^+$ in water or toothpaste), and a binary compound (e.g., $NaCl$). Write their formulas, their systematic IUPAC names, and locate their elements on the periodic table (group and period).

2. Home lab: Using a kitchen scale (uncertainty $\pm 1\text{ g}$), measure the mass of 1, 2, 3, 4, and 5 teaspoons of table salt ($NaCl$). Record the data in a table reflecting the experimental uncertainty and plot the graph of mass versus number of teaspoons.

3. Quantitative processing: Calculate the molar/formula mass of $NaCl$ from the atomic masses ($M_{\text{Na}} = 23.0\text{ u}$; $M_{\text{Cl}} = 35.5\text{ u}$). From the slope of your graph, calculate the average mass of a teaspoon and estimate how many formula units of salt it contains.

Assessment criteria:

• Correctness of formulas, IUPAC nomenclature, and location on the periodic table.

• Rigour in taking home measurements, expressing uncertainty, and plotting the graph.

• Precision in the calculations of atomic and molecular masses applied to the obtained data.