Learn more about Periodic Classification of Elements |
The physical properties of metals and non-metals, as we've discussed, come with a variety of exceptions that make classification based solely on these properties challenging. Let's summarise these exceptions:
Chemical properties of metals are the characteristics that describe how metals react with other substances and elements. Metals display a wide range of chemical properties, which are a result of their tendency to lose electrons and form positively charged ions (cations). Here are some key chemical properties of metals:
Metals vary in their reactivity. Some metals, like sodium and potassium, are highly reactive and readily react with air and water, while others, like gold and platinum, are much less reactive and remain unreactive in most conditions.
Reactivity Series (or Activity Series) of Metals
Reactivity Trends
Metals More Reactive Than Hydrogen
Metals Less Reactive Than Hydrogen
Many metals corrode when exposed to oxygen and moisture. For example, iron corrodes to form iron oxide (rust).
Example: 4Fe (s) + 3O2 (g) + 6H2O (l) → 4Fe(OH)3 (s) (Rust formation)
Alloys are mixtures of metals or metals with non-metals. They often have superior properties compared to pure metals. Brass, an alloy of copper and zinc, is stronger than pure copper.
Example: Brass - Cu (copper) + Zn (zinc)
Metals are crucial in electrochemical processes, like batteries. In a zinc-carbon battery, zinc undergoes oxidation and provides electrical energy.
Example: Zn (s) + 2MnO2 (s) + 2NH4Cl (aq) → ZnCl2 (aq) + 2MnO(OH) (s) + 2NH3 (aq)
Some metals, like platinum in catalytic converters, accelerate chemical reactions without being consumed themselves. In this case, platinum helps convert harmful exhaust gases into less harmful substances.
Example: Pt (platinum) catalysing the conversion of carbon monoxide (CO) to carbon dioxide (CO2) in an automobile exhaust system.
Most metals react with oxygen from the air to form metal oxides. This process is called oxidation.
The general equation for this reaction is:
Metal + Oxygen ? Metal Oxide
Example: When iron reacts with oxygen, it forms iron oxide (rust): 4Fe + 3O2 ? 2Fe2O3 (Iron oxide or rust)
The reactivity of metals with water varies. Some metals react vigorously with cold water, while others react only with steam or not at all.
The general equation for the reaction of metals with water is:
Metal + Water ? Metal Hydroxide + Hydrogen Gas
Example: Sodium reacts violently with cold water, producing sodium hydroxide and hydrogen gas: 2Na + 2H2O ? 2NaOH + H2
Most metals react with dilute acids, such as hydrochloric acid (HCl) or sulfuric acid (H2SO4), to produce salt and hydrogen gas.
The general equation for this reaction is: Metal + Dilute Acid → Salt + Hydrogen gas
Example: When zinc reacts with hydrochloric acid: Zn (s) + 2HCl (aq) → ZnCl2 (aq) + H2 (g)
Zinc displaces hydrogen from hydrochloric acid, forming zinc chloride and liberating hydrogen gas. This reaction is vigorous.
However, some metals like copper, silver, and gold do not react with dilute acids and remain unreactive.
When a more reactive metal is placed in the salt solution of a less reactive metal, a displacement reaction occurs.
The more reactive metal displaces the less reactive metal from the salt solution, forming its own salt solution and releasing the less reactive metal.
Example: When zinc is placed in copper sulphate solution: CuSO4 (aq) + Zn (s) → ZnSO4 (aq) + Cu (s)
Zinc displaces copper from copper sulphate solution, forming zinc sulphate and depositing copper metal.
Many metals react with chlorine gas (Cl2) to form metal chlorides.
The general equation for this reaction is: Metal + Chlorine → Metal Chloride
Example: When iron reacts with chlorine: 2Fe (s) + 3Cl2 (g) → 2FeCl3 (s)
Iron combines with chlorine to form iron(III) chloride, a reddish-brown solid.
Some very reactive metals, like sodium, potassium, calcium, and magnesium, can react with hydrogen gas to form metal hydrides.
The general equation for this reaction is: Metal + Hydrogen → Metal Hydride
Example: When sodium reacts with hydrogen: 2Na (s) + H2 (g) → 2NaH (s)
Sodium reacts with hydrogen to form sodium hydride, a solid compound.
Aqua-regia, often referred to as "royal water," is a highly corrosive and potent mixture of concentrated nitric acid (HNO3) and concentrated hydrochloric acid (HCl). It is called "royal water" because of its ability to dissolve noble metals like gold and platinum, which are typically resistant to most acids. Here are some key characteristics and uses of aqua-regia:
Chemical properties and reactions of non-metals are quite distinct from those of metals. Non-metals, being on the right side of the periodic table, generally have a tendency to gain or share electrons in chemical reactions. Here are the key chemical properties and reactions of non-metals:
Non-metals generally have high electronegativity, meaning they have a strong tendency to attract electrons when they participate in chemical reactions. This property allows them to form covalent bonds by sharing electrons with other non-metals or with hydrogen.
Non-metals often form covalent compounds, where atoms share electrons to achieve a stable electron configuration. In covalent bonds, electrons are shared rather than transferred as in ionic bonds.
Non-metals often react with oxygen to form oxides. These oxides can be acidic or neutral.
Acidic oxides: Non-metals like carbon, sulphur, and nitrogen form acidic oxides (e.g., CO2, SO2). When these oxides dissolve in water, they produce acids (e.g., carbonic acid, sulphurous acid).
For example: C + O2 → CO2
CO2 + H2O → H2CO3 (Carbonic Acid)
Neutral oxides: Some non-metals like hydrogen and oxygen form neutral oxides (e.g., H2O). These oxides do not affect the pH of water and are not acidic.
Non-metals do not generally react with water or steam to produce hydrogen gas (H2). Unlike metals, they lack the ability to donate electrons to reduce water molecules into hydrogen gas and hydroxide ions (OH-).
Non-metals do not readily react with dilute acids. They do not displace hydrogen ions (H+) from acids because they are not good electron donors.
In some cases, a more reactive non-metal can displace a less reactive non-metal from its salt solution. This displacement reaction forms new compounds.
For instance, chlorine gas (Cl2) can displace bromine (Br2) from a solution of sodium bromide (NaBr), resulting in the formation of sodium chloride (NaCl) and bromine gas (Br2).
Cl2 + NaBr → NaCl + Br2
Non-metals can react with chlorine gas (Cl2) to form covalent chlorides. These chlorides are typically covalent compounds and do not conduct electricity.
Examples include hydrogen chloride (HCl) formed by the reaction of hydrogen (H2) with chlorine (Cl2) and phosphorus trichloride (PCl3) formed by the reaction of phosphorus (P4) with chlorine.
P4 + 6Cl2 → 4PCl3
Non-metals can react with hydrogen gas (H2) to form covalent hydrides. These hydrides involve the sharing of electrons and are typically covalent compounds.
Examples include hydrogen sulphide (H2S) formed by sulphur's reaction with hydrogen and ammonia (NH3) formed by nitrogen's reaction with hydrogen.
Non-metal hydrides do not contain ions and do not conduct electricity.
Non-metals can react with halogens like fluorine (F2), chlorine (Cl2), bromine (Br2), and iodine (I2) to form various covalent compounds.
For example, iodine reacts with hydrogen to form hydrogen iodide (HI).
Metals and non-metals react with each other differently due to their distinct chemical properties. The way they react depends on the number of electrons in their outermost energy levels (valence electrons) and their tendency to gain or lose electrons.
A chemical bond is the force of attraction that holds atoms (or ions) together in a molecule or compound. It is the result of interactions between electrons in the outermost energy levels (valence electrons) of atoms.
Atoms tend to combine with each other because they seek to achieve a stable electron configuration, specifically, the electron arrangement of an inert gas (also known as a noble gas). Inert gases have a full outermost electron shell, which makes them highly stable and unreactive.
Learn more about Occurence of Metals |
Ions are electrically charged particles that result from the gain or loss of one or more electrons by an atom. Ions can be either positively charged (cations) or negatively charged (anions), depending on whether they have lost or gained electrons.
Cations (Positive Ions)
Anions (Negative Ions)
Ionic bonds are formed between ions, typically a cation and an anion. These bonds result from the electrostatic attraction between oppositely charged ions. Ionic bonds are characterised by the transfer of electrons from one atom to another, leading to the formation of a compound with a neutral overall charge. Here's how ionic bonds are formed:
Example 1: Sodium Chloride (NaCl)
Sodium (Na) is a metal and readily loses its one valence electron to form Na+.
Chlorine (Cl) is a non-metal and readily gains an electron to form Cl-.
When sodium donates its electron to chlorine, they become oppositely charged ions (Na+ and Cl-).
The electrostatic attraction between Na+ and Cl- ions results in the formation of the ionic compound sodium chloride (NaCl), also known as table salt.
Example 2: Calcium Oxide (CaO)
Calcium (Ca) is a metal that loses two valence electrons to form Ca2+.
Oxygen (O) is a non-metal that gains two electrons to form O2-.
When calcium and oxygen combine, Ca2+ and O2- ions are attracted to each other, forming the ionic compound calcium oxide (CaO).
Ionic compounds are chemical compounds formed through the combination of positively charged ions (cations) and negatively charged ions (anions). These compounds are also known as salts. Ionic compounds are typically composed of a metal cation and a non-metal anion, although there are exceptions.
Key Properties of Ionic Compounds:
1. Where are metals and non-metals found in the periodic table?
Metals are generally found on the left and middle of the periodic table, while non-metals are located on the right side. There is a zigzag line separating metals from non-metals; elements along this line are called metalloids, which have properties of both metals and non-metals.
2. What is the cause of chemical bonding between elements?
Chemical bonding occurs because atoms seek to achieve a stable electronic configuration, typically by filling their outermost electron shell. This can be achieved by sharing electrons (covalent bonds), transferring electrons (ionic bonds), or delocalising electrons in metallic bonds.
3. How do metals and non-metals react with each other?
Metals tend to lose electrons and form positive ions (cations), while non-metals tend to gain electrons to form negative ions (anions). When metals and non-metals react, they form ionic compounds through the transfer of electrons from the metal to the non-metal.
Example: Sodium (metal) reacts with chlorine (non-metal) to form sodium chloride (ionic compound).
4. What are alloys, and why are they important in metallurgy?
Mixtures of two or more elements, at least one of which is a metal, are called alloys. Since they frequently have better qualities than pure metals, such as greater strength, hardness, and corrosion resistance, they are significant in metallurgy. Bronze and steel are two examples.
5. Why do metals lose electrons while non-metals gain electrons during reactions?
Metals have few electrons in their outermost shell, making it easier for them to lose electrons and achieve a stable electron configuration. Non-metals have more electrons in their outer shell, so they tend to gain electrons to complete their shell and become stable.
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