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Disorders of the Digestive System - Causes, Symptoms & Treatment Disorders of the Digestive System: Causes, Symptoms, Treatment & Prevention 1. Introduction to Digestive Disorders The digestive system breaks down food and absorbs nutrients. Disorders like acid reflux, IBS, or ulcers can interfere with these processes. Understanding symptoms, causes, and treatments is essential for maintaining gut health. 2. Common Digestive System Disorders Acid Reflux (GERD): Stomach acid flows into the esophagus causing heartburn. Peptic Ulcers: Open sores in the stomach or small intestine. Irritable Bowel Syndrome (IBS): Affects bowel habits with cramping and bloating. Constipation: Infrequent or painful bowel movements. Diarrhea: Loose, frequent stools. Inflammatory Bowel Disease (IBD): Includes Crohn's disease and ulcerative colitis. Gallstones: Block bile flow, causing pain an...
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Why Do Atoms Form Chemical Bonds? – MCQs & Short Questions

 

hy Do Atoms Form Chemical Bonds?

Introduction

Atoms do not exist alone in nature. They combine with other atoms to form molecules or compounds. But why do they do this? The answer lies in stability—atoms form chemical bonds to achieve a low-energy, stable state, just like noble gases.

1. The Role of Noble Gases

Scientists discovered that noble gases (such as helium, neon, and argon) do not react with other elements because their outermost electron shells are full.

  • Helium (He) has 2 electrons in its outer shell.
  • Other noble gases have 8 electrons in their outer shell.

Since these gases do not form bonds, scientists realized that a full outer shell makes an atom stable. This led to the Octet Rule.

Octet Rule

"Atoms tend to gain, lose, or share electrons to complete 8 electrons in their outermost shell (or 2 for hydrogen and helium) to achieve stability."

2. How Do Atoms Achieve Stability?

Atoms that do not have a full outer shell can achieve stability in three ways:

1. Losing Electrons → Forms Positive Ions (Cations)

  • Some atoms (like sodium) lose electrons to get a full outer shell.

2. Gaining Electrons → Forms Negative Ions (Anions)

  • Some atoms (like chlorine) gain electrons to complete their outer shell.

3. Sharing Electrons → Forms Covalent Bonds

  • Some atoms (like oxygen) share electrons to complete their outer shell.
  • Example: Oxygen molecule (O₂)
    • Each oxygen atom shares 2 electrons to form a stable O₂ molecule.

Conclusion

Atoms form chemical bonds because they want to be stable. By following the Octet Rule, they lose, gain, or share electrons to achieve a low-energy state—just like noble gases. This process leads to the formation of ionic, covalent, or metallic bonds, which hold atoms together in compounds and molecules.


Multiple-Choice Questions (MCQs)

1. Why do atoms form chemical bonds?
a) To increase their energy
b) To become unstable
c) To achieve stability
d) To change their atomic number
→ (c) To achieve stability

2. What is the Octet Rule?
a) Atoms tend to lose, gain, or share electrons to complete 6 electrons in their outermost shell
b) Atoms tend to lose, gain, or share electrons to complete 8 electrons in their outermost shell
c) Atoms always lose electrons to become stable
d) Atoms always gain electrons to become stable
→ (b) Atoms tend to lose, gain, or share electrons to complete 8 electrons in their outermost shell

3. Which of the following elements is already stable?
a) Hydrogen
b) Neon
c) Sodium
d) Oxygen
→ (b) Neon

4. What happens when an atom loses an electron?
a) It becomes a negative ion
b) It becomes a positive ion
c) It remains neutral
d) It becomes unstable
→ (b) It becomes a positive ion

5. What happens when an atom gains an electron?
a) It becomes a positive ion
b) It becomes a negative ion
c) It remains neutral
d) It releases energy
→ (b) It becomes a negative ion

6. What type of bond is formed when electrons are transferred?
a) Ionic bond
b) Covalent bond
c) Metallic bond
d) Hydrogen bond
→ (a) Ionic bond

7. What type of bond is formed when electrons are shared?
a) Ionic bond
b) Covalent bond
c) Metallic bond
d) Hydrogen bond
→ (b) Covalent bond

8. Which type of elements usually form ionic bonds?
a) Metal and metal
b) Non-metal and non-metal
c) Metal and non-metal
d) Noble gases
→ (c) Metal and non-metal

9. What kind of bond is found in water (H₂O)?
a) Ionic bond
b) Covalent bond
c) Metallic bond
d) Hydrogen bond
→ (b) Covalent bond

10. Which of the following is an example of an ionic bond?
a) H₂O
b) O₂
c) NaCl
d) CO₂
→ (c) NaCl

11. What is the charge on a sodium ion (Na⁺) after losing an electron?
a) -1
b) 0
c) +1
d) +2
→ (c) +1

12. What is the charge on a chlorine ion (Cl⁻) after gaining an electron?
a) -1
b) 0
c) +1
d) +2
→ (a) -1

13. What type of bond exists between two oxygen atoms in an O₂ molecule?
a) Ionic bond
b) Covalent bond
c) Metallic bond
d) Hydrogen bond
→ (b) Covalent bond

14. Which bond allows free movement of electrons in metals?
a) Ionic bond
b) Covalent bond
c) Metallic bond
d) Hydrogen bond
→ (c) Metallic bond

15. Why do noble gases not form chemical bonds easily?
a) They are highly reactive
b) They already have a complete outer shell
c) They need to gain electrons
d) They have an unstable nucleus
→ (b) They already have a complete outer shell

16. What happens to atoms when they form a chemical bond?
a) Their energy increases
b) They become unstable
c) Their energy decreases
d) They lose protons
→ (c) Their energy decreases

17. Which of the following is an example of a covalent compound?
a) NaCl
b) H₂O
c) KBr
d) CaO
→ (b) H₂O

18. Which of these is NOT a type of chemical bond?
a) Ionic bond
b) Covalent bond
c) Metallic bond
d) Radioactive bond
→ (d) Radioactive bond

19. Which of these atoms is most likely to lose an electron?
a) Sodium (Na)
b) Chlorine (Cl)
c) Oxygen (O)
d) Fluorine (F)
→ (a) Sodium (Na)

20. What kind of bond holds atoms together in metals?
a) Ionic bond
b) Covalent bond
c) Metallic bond
d) Hydrogen bond
→ (c) Metallic bond

Short Questions

1. Why do atoms form chemical bonds?
Atoms form chemical bonds to achieve stability by lowering their energy.

2. What is the Octet Rule?
The Octet Rule states that atoms tend to gain, lose, or share electrons to complete 8 electrons in their outer shell, making them stable like noble gases.

3. How does a sodium atom become a sodium ion?
A sodium atom (Na) loses one electron to form a positive ion (Na⁺).

4. How does a chlorine atom become a chloride ion?
A chlorine atom (Cl) gains one electron to form a negative ion (Cl⁻).

5. What is an ionic bond?
An ionic bond is formed when electrons are transferred from one atom to another, creating positive and negative ions that attract each other.

6. What is a covalent bond?
A covalent bond is formed when two atoms share electrons to complete their outer shells.

7. What is a metallic bond?
A metallic bond is a bond in which metal atoms share a "sea of electrons," allowing electrical conductivity.

8. Why are noble gases unreactive?
Noble gases are unreactive because their outermost electron shells are already full.

9. Give an example of an ionic compound.
Sodium chloride (NaCl) is an example of an ionic compound.

10. Give an example of a covalent compound.
Water (H₂O) is an example of a covalent compound.

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