The Periodic Table 🌌

The periodic table is a chart of elements placed according to the order of increasing atomic numbers. Atomic number is the property of elements used to place them in order on the periodic table. 🔢

Important Features of the Periodic Table 📊

• Elements are arranged in the order of increasing atomic numbers. 🔢
• Elements with similar electronic configurations are placed in the same group. 🔗
• Elements with similar chemical properties are placed in the same group. 🧪

Period 📅

A period is a horizontal row of elements in the periodic table. The periodic table has 7 periods. 📏

• Period 1 contains two elements; hydrogen and helium. 💧🎈
• Periods 2 and 3 contain eight elements each and are called short periods. 📏
• Periods 4, 5 and 6 contain eighteen elements each and are called long periods. 📏
• Period 7 contains three elements. 🔢

Progression of Properties Across the Period 🔄

As we move across the period (from left to right):

• The metallic nature of elements decreases. They change from metals to non-metals and inert gases. ⚖️
• Electronegativity increases. ⚡
• The atomic number increases by one between successive elements. ➕
• The number of shells remains the same while the number of valence electrons increases steadily. 📈

Groups 📊

A group is a vertical column of elements in the periodic table. There are eight groups on the periodic table, labeled with Roman numerals. 🏛️

Position of Hydrogen in the Periodic Table 💧

Hydrogen is placed between Group I and Group VII because it behaves like both. It can lose one electron to form a hydrogen ion or gain one to form a hydride ion. ⚛️

Group I Elements (Alkali Metals) 🔥

Alkali metals react with water to form alkalis. They are stored under oil to prevent reactions with air or water. 💧

Group VII Elements (Halogens) 🌈

Group VII elements are also known as Halogens because they react with metals to form salts. The term "halogen" means "salt-former". 🧂

Group O Elements (Noble Gases) 🎈

Group O elements, also known as Noble gases, are unreactive due to their full outer electron shells. 🛡️

Transition Elements 🔄

Transition elements are found in the center block of the periodic table, between Groups II and III, and through Periods 4 and 6. They are all metals with unique properties. ⚙️

Practice Questions ❓

Use the following examples and exercises to test your understanding of the periodic table. 📚

Example 📝

Using the following evidence, determine the group numbers for elements A, B, C, D, and E on the periodic table:

Periodic Table of Elements

Important Features of the Periodic Table

• Elements are arranged in the order of increasing atomic numbers.
• Elements with similar electronic configurations are placed in the same group.
• Elements with similar chemical properties are placed in the same group.

Period

A period is a horizontal row of elements in the periodic table. The periodic table has 7 periods.

• Period 1 contains two elements; hydrogen and helium.
• Periods 2 and 3 contain eight elements each and are called short periods.
• Periods 4, 5 and 6 contain eighteen elements each and are called long periods.
• Period 7 contains three elements.

Progression of Properties Across the Period

As we move across the period (from left to right):

• The metallic nature of elements decreases. They change from metals to non-metals and inert gases.
• Electronegativity increases.
• The atomic number increases by one between successive elements.
• The number of shells remains the same while the number of valence electrons increases steadily.

Groups

A group is a vertical column of elements in the periodic table. There are eight groups on the periodic table, labeled with Roman numerals.

• Group I: Alkali metals 🔥
• Group II: Alkaline earth metals 🌍
• Group VII: Halogens 🌈
• Group O: Noble gases/Inert gases 🎈

Position of Hydrogen in the Periodic Table 💧

Hydrogen is placed between Group I and Group VII because it behaves like both. It can lose one electron to form a hydrogen ion or gain one to form a hydride ion. ⚛️

The groups on the periodic table have distinct properties:

Group I Elements (Alkali Metals) 🔥

Alkali metals react with water to form alkalis. They are stored under oil to prevent reactions with air or water. 💧

Trend in Chemical Reactivity of Group I Elements 📈

The reactivity of Group I elements increases as you go down the group. Lithium is the least reactive, while francium is the most reactive element in Group I. ⚡

Group II Elements (Alkaline Earth Metals) 🌍

Group II elements are known as Alkaline Earth Metals because they form alkaline solutions when reacting with water. They are characterized by having two electrons in their outer shell, which they readily lose to form +2 ions. ⚛️

The reactivity of alkaline earth metals increases down the group, with barium being more reactive than magnesium. They react with water to form hydroxides and release hydrogen gas. ⚡

Chemical Properties of Group II Elements 🧪

Alkaline earth metals are less reactive than alkali metals but still react with acids to produce hydrogen gas. They also form oxides and hydroxides that are basic in nature. ⚗️

Uses of Group II Elements 🛠️

• Magnesium is used in fireworks and as a lightweight structural material in aerospace applications. ✈️
• Calcium is essential for living organisms, particularly in bones and teeth. 🦴
• Barium is used in medical imaging to enhance the contrast of X-ray images. 📸

Group VII Elements (Halogens) 🌈

Group VII elements are also known as Halogens because they react with metals to form salts. The term "halogen" means "salt-former". 🧂

The reactivity of halogens increases as you go up the group, with fluorine being the most reactive and astatine the least reactive. ⚡

Chemical Properties of Group VII Elements 🧪

Halogens have seven electrons in their outer shell, making them strong oxidizing agents. They readily accept electrons to form ions with a 1− charge. ⚡

Uses of Group VII Elements 🛠️

• Fluorine is used in toothpaste to prevent tooth decay. 🦷
• Chlorine is used to sterilize drinking water. 💧
• Iodine is added to table salt to prevent goiter. 🧂

Group O Elements (Noble Gases) 🎈

Group O elements, also known as Noble gases, are unreactive due to their full outer electron shells. 🛡️

Transition Elements 🔄

Transition elements are found in the center block of the periodic table, between Groups II and III, and through Periods 4 and 6. They are all metals with unique properties. ⚙️

Physical Properties of Transition Elements ⚙️

• High densities ⚖️
• High melting and boiling points 🔥
• Good conductors of heat and electricity ⚡
• Mostly solid at room temperature (except mercury, which is a liquid) 🌡️
• Ductile and malleable 🔨

Chemical Properties of Transition Elements 🧪

• They act as catalysts in various reactions. ⚗️
• They have variable valencies and form positively charged ions. ➕
• They form colored compounds depending on their valency. 🎨

Uses of Transition Elements 🛠️

• Used to make electric cables and cookware due to their conductivity. ⚡
• Used to form alloys, such as brass (copper and zinc) and bronze (copper and tin). ⚒️
• Used as catalysts in industrial processes (e.g., iron in the Haber process). ⚗️

Practice Questions ❓

Use the following examples and exercises to test your understanding of the periodic table. 📚

Example 📝

Using the following evidence, determine the group numbers for elements A, B, C, D, and E on the periodic table:

• A: An oxide A₂O exists and is strongly basic. 🔥
• B: Forms a liquid covalent chloride. 💧
• C: The oxide of C is acidic. ⚗️
• D: Produces a positively charged ion. ➕
• E: Exists as an unreactive monatomic element. ⚛️

Solution: Group I, Group V, Group III, Group VII, Group O. ✅

Exercise 📝

1. The diagram below shows part of the periodic table. Answer the following questions using the elements shown:
   • Write down the symbol for an element with five electrons in the outermost shell. 🔍
   • Identify a diatomic molecule. 🔗
   • Find an element that reacts with sodium to form sodium bromide. ⚗️
   • Identify a noble gas. 🎈
   • Find an element with a lower atomic number than fluorine. 🔢
2. Why is argon very unreactive? 🤔
3. Name the element in Group II and Period 3 on the periodic table. Is it a metal or non-metal? ⚖️
4. Suggest the formula of a compound formed between the element from (2) and sulfur (S). ⚗️
5. Explain why chlorine and fluorine have similar chemical properties. 🔄

Further Exercises 🔍

6. Chlorine, bromine, and iodine are ordered as follows in Group VII:
   • State four ways in which the physical or chemical properties of chlorine, bromine, and iodine are similar. 🔄
   • Describe the trends in physical properties among chlorine, bromine, and iodine. 📈
   • Explain how the trend in chemical reactivity is shown by displacement reactions. Provide an equation for a reaction where one halogen displaces another from its compound. ⚗️
7. The diagram below shows a table of elements extracted from a larger periodic table. Based on the table:
   • Identify the group containing halogens. 🌈
   • Identify the group containing alkali metals. 🔥
   • Select a metal from Period 2. ⚖️
   • Select a non-metal with a valency of 2. ⚗️
8. Explain the classification challenge for hydrogen, as it resembles both chlorine and sodium in certain ways:
   • How many electrons does a hydrogen atom contain? 🔢
   • What is the valency of hydrogen? ➕
   • In what way is hydrogen similar to chlorine? 🔄
   • In what way is hydrogen similar to sodium? 🔄
9. Using the periodic table, answer the following:
   • Provide the symbol of a non-metal used to sterilize water. 💧
   • Identify an element that forms diatomic molecules. 🔗
   • Find an element that reacts with water to create an alkaline solution. ⚗️
   • Choose an element that forms an ion with a 2− charge. ➖
10. Oxygen, sulfur, and selenium belong to Group VI of the periodic table. Given that at room temperature:
    • Oxygen is a gas and sulfur is a solid, predict whether selenium is likely a liquid, solid, or gas. 🔍
    • Identify the most reactive element in Group VII based on the reactivity trend similar to Group VI. ⚡