HKDSE Chemistry Core
Section 2: Microscopic World I | 微觀世界 I
Billy Sir’s Smart Notes: Master Atomic Structure, Chemical Bonding, and the 4 Giant/Simple Structures.
由資深導師 Billy Sir 編寫，助你極速掌握原子結構、化學鍵及四大結構與性質。
1. Atomic Structure & Isotopes | 原子結構與同位素
An atom consists of a central nucleus (containing protons and neutrons) surrounded by electrons in electron shells. 原子由中心的原子核（包含質子和中子）及外圍電子層中的電子組成。
🔬 Isotopes | 同位素
Isotopes are different atoms of the same element that have the same number of protons but a different number of neutrons. 同位素是具有相同質子數，但中子數不同的同種元素原子。
- They have the same chemical properties because they have the same electronic arrangement. (它們具有相同的化學性質，因為電子排佈相同。)
- They have different physical properties (e.g., density, mass) due to different numbers of neutrons. (由於中子數不同，它們的物理性質如密度、質量會有所不同。)
2. Electronic Arrangement & Periodic Table | 電子排佈與週期表
The arrangement of electrons in an atom determines its position in the Periodic Table and its chemical behavior. 原子中電子的排佈決定了它在週期表中的位置及其化學行為。
- Period (週期): The horizontal rows. The period number equals the number of occupied electron shells.
橫行。週期數等於已佔用的電子層數。 - Group (族): The vertical columns. The group number equals the number of outermost shell (valence) electrons.
直行。族數等於最外層（價）電子數。
Example: Sodium (Na) has an atomic number of 11. Its electronic arrangement is 2, 8, 1. Therefore, it is in Period 3 and Group I. (例子：鈉的原子序為11，電子排佈為 2, 8, 1。因此它位於第3週期、第I族。)
3. Chemical Bonding | 化學鍵
Atoms bond together to achieve a stable noble gas electronic arrangement (octet or duplet). 原子透過鍵結來達到穩定的貴氣體電子排佈（八隅體或雙電子）。
| Bond Type (鍵型) | Formation (形成方式) | Nature of Attraction (引力本質) |
|---|---|---|
| Ionic Bond 離子鍵 |
Transfer of electrons from metal to non-metal. 電子由金屬轉移至非金屬。 |
Strong electrostatic attraction between oppositely charged ions. 帶相反電荷離子間的強大靜電引力。 |
| Covalent Bond 共價鍵 |
Sharing of outermost electrons between non-metals. 非金屬之間共用最外層電子。 |
Strong electrostatic attraction between shared electrons and two nuclei. 共用電子與兩個原子核間的強大靜電引力。 |
| Metallic Bond 金屬鍵 |
Metal atoms lose outer electrons to form a “sea of electrons”. 金屬原子失去外層電子形成「電子海」。 |
Strong electrostatic attraction between positive metal ions and delocalized electrons. 金屬陽離子與離域電子間的強大靜電引力。 |
4. Structures and Properties | 結構與性質
⚠️ Exam Trap: Bonding vs. Structure | 考試陷阱：化學鍵 vs 結構
Never confuse “Bonding” (the glue) with “Structure” (the 3D arrangement). For example, water (\(H_2O\)) has covalent bonds between H and O atoms, but its overall structure is a simple molecular structure. When boiling water, we break the weak intermolecular forces, NOT the strong covalent bonds! 千萬不要混淆「化學鍵」（黏合劑）和「結構」（立體排列）。例如，水分子內有共價鍵，但整體是簡單分子結構。沸騰時，我們打破的是微弱的分子間引力，而不是強大的共價鍵！
| Structure (結構) | Examples (例子) | Melting & Boiling Point (熔點及沸點) | Electrical Conductivity (導電性) |
|---|---|---|---|
| Giant Ionic Structure 巨型離子結構 |
\( \text{NaCl} \), \( \text{MgO} \) | High: A lot of heat is needed to overcome strong ionic bonds. 高：需大量熱能克服強大的離子鍵。 |
Molten/Aqueous only: Mobile ions are present. Solid state has no mobile ions. 僅在熔融/水溶液態導電：有流動離子。 |
| Giant Covalent Structure 巨型共價結構 |
Diamond (鑽石), Quartz (\( \text{SiO}_2 \)) | Very High: A lot of heat is needed to break the extensive network of strong covalent bonds. 極高：需大量熱能打破龐大的共價鍵網絡。 |
Non-conductor: No mobile electrons/ions. (Exception: Graphite conducts due to delocalized electrons) 不導電：無流動電子/離子。(石墨例外) |
| Giant Metallic Structure 巨型金屬結構 |
\( \text{Fe} \), \( \text{Cu} \) | High: A lot of heat is needed to overcome strong metallic bonds. 高：需大量熱能克服強大的金屬鍵。 |
Good conductor (All states): Contains a “sea” of delocalized mobile electrons. 優良導體(所有狀態)：含有流動的離域電子。 |
| Simple Molecular Structure 簡單分子結構 |
\( \text{H}_2\text{O} \), \( \text{CO}_2 \), \( \text{I}_2 \) | Low: Only a little heat is needed to overcome the weak intermolecular forces (Van der Waals’ forces). 低：只需少量熱能克服微弱的分子間引力。 |
Non-conductor: Molecules are neutral and have no mobile electrons or ions. 不導電：分子呈中性，無流動電子或離子。 |
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