SAT2 Chemistry: Comprehensive Knowledge Summary | SAT2化学知识点总结

📚 SAT2 Chemistry: Comprehensive Knowledge Summary | SAT2化学知识点总结

The SAT Subject Test in Chemistry assesses your ability to apply fundamental chemical principles. This article summarizes essential topics, key formulas, and high-yield facts to help you achieve a top score. Master these concepts, and you’ll be ready for any question the test throws at you.

SAT2 化学考试评估学生对基本化学原理的应用能力。本文梳理了必考知识点、关键公式和常考高频内容，助你冲刺满分。吃透这些概念，你就能从容应对考试中的任何问题。

1. Atomic Structure and Electron Configuration | 原子结构与电子排布

Atoms consist of protons (positive), neutrons (neutral), and electrons (negative). The atomic number Z equals the number of protons and determines the element. Mass number A = protons + neutrons.

原子由质子（正电）、中子（中性）和电子（负电）组成。原子序数Z等于质子数，决定元素种类。质量数A = 质子数 + 中子数。

Isotopes of an element have the same number of protons but different numbers of neutrons, leading to different mass numbers. The relative atomic mass is a weighted average of all naturally occurring isotopes.

元素的同位素质子数相同而中子数不同，因此质量数不同。相对原子质量是各种天然同位素的加权平均值。

Electrons occupy energy levels (shells) and subshells (s, p, d, f). The s subshell holds 2 electrons, p holds 6, d holds 10, and f holds 14. The electron configuration of carbon is 1s²2s²2p².

电子占据能层和亚层（s, p, d, f）。s 亚层可容纳 2 个电子，p 可容纳 6 个，d 可容纳 10 个，f 可容纳 14 个。碳原子的电子排布式为 1s²2s²2p²。

Hund’s rule states that electrons fill degenerate orbitals singly with parallel spins before pairing. The Pauli exclusion principle asserts that no two electrons can have the same set of four quantum numbers.

洪特规则指出，电子在能量相同的轨道上尽可能分占不同轨道，且自旋平行，再配对。泡利不相容原理表明，同一原子中没有两个电子具有完全相同的四个量子数。

Fe: [Ar] 4s²3d⁶ | Note half-filled and fully-filled stability (e.g., Cr: [Ar] 4s¹3d⁵)

Fe: [Ar] 4s²3d⁶ | 注意半充满和全充满的稳定性（如 Cr: [Ar] 4s¹3d⁵）

2. Periodic Table and Periodicity | 周期表与周期性规律

The periodic table is organized by increasing atomic number. Periods run horizontally, groups run vertically. Elements in the same group have similar valence electron configurations and comparable chemical properties.

周期表按原子序数递增排列。横行称为周期，纵列称为族。同族元素具有相似的价电子排布和相近的化学性质。

Atomic radius decreases across a period due to increased nuclear charge pulling electrons closer. It increases down a group because additional electron shells are added.

同一周期中，原子半径从左到右减小，因为核电荷增加将电子拉得更紧。同一族中从上到下原子半径增大，因为电子层数增加。

Ionization energy (IE) generally increases across a period and decreases down a group. The first ionization energy is the energy required to remove the outermost electron. Metals have low IE, nonmetals high IE.

电离能（IE）在同一周期中一般从左到右增大，同族从上到下减小。第一电离能指移除最外层电子所需的能量。金属电离能低，非金属电离能高。

Electron affinity (EA) becomes more negative across a period (more energy released when gaining an electron). Electronegativity, the ability to attract bonding electrons, follows the same trend: increases across a period, decreases down a group.

电子亲和能（EA）在同一周期中变得更负（获得电子时放出更多能量）。电负性衡量原子吸引键合电子的能力，变化趋势相同：同周期递增，同族递减。

F > O > Cl > N > Br > I > S > C > H ≈ P … for electronegativity

电负性顺序：F > O > Cl > N > Br > I > S > C > H ≈ P …

3. Chemical Bonding and Intermolecular Forces | 化学键与分子间作用力

Ionic bonds form between metals and nonmetals through electron transfer. Cations (positive) and anions (negative) are held together by electrostatic forces. Covalent bonds involve electron sharing, typically between nonmetals.

离子键由金属和非金属通过电子转移形成。阳离子（正电）和阴离子（负电）通过静电引力结合在一起。共价键涉及非金属原子之间的电子共享。

Polar covalent bonds arise when electrons are shared unequally due to electronegativity difference (ΔEN). A ΔEN > 1.7 usually indicates ionic character; ΔEN < 0.4 is nonpolar covalent.

极性共价键源于电负性差异导致的电子共享不均。ΔEN ＞ 1.7 通常属于离子键；ΔEN ＜ 0.4 为非极性共价键。

Metallic bonding consists of a sea of delocalized electrons surrounding positive metal ions, explaining conductivity and malleability.

金属键由离域电子海与正金属离子构成，解释了金属的导电性和延展性。

Intermolecular forces (IMFs) determine physical properties like boiling point. London dispersion forces exist in all molecules and increase with molecular size. Dipole-dipole forces occur in polar molecules. Hydrogen bonding, a strong dipole interaction, occurs when H is bonded to N, O, or F.

分子间作用力（IMFs）决定沸点等物理性质。伦敦色散力存在于所有分子中，随分子尺寸增大而增强。偶极-偶极力存在于极性分子中。氢键是一种强偶极作用，当H与N、O或F相连时产生。

Boiling point: H₂O > H₂S > H₂Se due to hydrogen bonding

沸点：H₂O > H₂S > H₂Se（因氢键存在）

4. Molecular Geometry and VSEPR Theory | 分子几何与VSEPR理论

VSEPR (Valence Shell Electron Pair Repulsion) theory predicts molecular shape by assuming electron pairs around a central atom repel and arrange to minimize repulsion. Both bonding pairs and lone pairs are considered.

VSEPR（价层电子对互斥）理论通过假定中心原子周围的电子对互相排斥并采取最小排斥的排列来预测分子形状。考虑成键电子对和孤电子对。

2 electron pairs → linear (180°), e.g. BeCl₂. 3 electron pairs → trigonal planar (120°), e.g. BF₃. 4 electron pairs → tetrahedral (109.5°), e.g. CH₄. With one lone pair, pyramidal (107°), e.g. NH₃. With two lone pairs, bent (104.5°), e.g. H₂O.

2 对电子 → 直线形（180°），如 BeCl₂。3 对电子 → 平面三角形（120°），如 BF₃。4 对电子 → 四面体形（109.5°），如 CH₄。有一对孤电子，三角锥形（107°），如 NH₃。有两对孤电子，V 形（104.5°），如 H₂O。

Hybrid orbitals correspond to electron-domain geometry: sp for linear, sp² for trigonal planar, sp³ for tetrahedral. Multiple bonds count as one electron domain.

杂化轨道对应于电子域几何：sp 杂化对应直线形，sp² 对应平面三角形，sp³ 对应四面体形。多重键只算作一个电子域。

CO₂: O=C=O, linear, sp hybridization

CO₂: O=C=O，直线形，sp 杂化

5. Stoichiometry and Reactions | 化学计量与反应类型

The mole is the chemist’s counting unit, 6.022 × 10²³ particles. Molar mass (g/mol) links mass to moles. Empirical formulas give the simplest whole-number ratio of atoms; molecular formulas are multiples of the empirical formula.

摩尔是化学家的计数单位，6.022 × 10²³ 个粒子。摩尔质量（g/mol）连接质量与物质的量。实验式给出原子最简整数比；分子式是实验式的整数倍。

Percent composition: % element = (mass of element / molar mass of compound) × 100%. Limiting reactant problems require comparing mole ratios; the reactant that produces least product is limiting.

质量分数：某元素% =（该元素质量 / 化合物摩尔质量）× 100%。限量反应物问题需要比较摩尔比；生成产物最少的反应物就是限量反应物。

Reaction types: Synthesis (A + B → AB), Decomposition (AB → A + B), Single displacement (A + BC → AC + B), Double displacement (AB + CD → AD + CB), Combustion (hydrocarbon + O₂ → CO₂ + H₂O).

反应类型：化合反应（A + B → AB）、分解反应（AB → A + B）、置换反应（A + BC → AC + B）、复分解反应（AB + CD → AD + CB）、燃烧反应（烃 + O₂ → CO₂ + H₂O）。

Balancing equations ensures conservation of mass and charge. Start with most complex species; balance O and H last.

配平化学方程式遵循质量守恒和电荷守恒。从最复杂的物质入手，最后配平O和H。

2H₂ + O₂ → 2H₂O

6. Gases and Gas Laws | 气体与气体定律

The Ideal Gas Law: PV = nRT, where R = 0.0821 L·atm/mol·K or 8.314 J/mol·K. STP conditions: 0°C (273 K) and 1 atm. At STP, one mole of an ideal gas occupies 22.4 L.

理想气体状态方程：PV = nRT，R = 0.0821 L·atm/mol·K 或 8.314 J/mol·K。标准状况 STP：0°C (273 K)，1 atm。标准状况下，1 mol 理想气体占据 22.4 L。

Dalton’s Law of Partial Pressures: P_total = P₁ + P₂ + … . Each gas behaves independently. Graham’s Law of Effusion: rate ∝ 1/√(molar mass).

道尔顿分压定律：总压 P_total = P₁ + P₂ + …，各组分气体独立作用。格雷姆扩散定律：扩散速率 ∝ 1/√（摩尔质量）。

Combined Gas Law: P₁V₁/T₁ = P₂V₂/T₂. Kinetic Molecular Theory: gas particles are in constant random motion, with negligible volume and no intermolecular forces; average kinetic energy ∝ temperature.

综合气体定律：P₁V₁/T₁ = P₂V₂/T₂。气体分子运动论：气体微粒做无规则运动，自身体积可忽略，分子间无作用力；平均动能与温度成正比。

Real gases deviate at high pressure and low temperature because of particle volume and intermolecular attractions. Van der Waals equation accounts for these deviations.

真实气体在高压低温下偏离理想行为，因为微粒本身的体积和分子间引力不可忽略。范德华方程对此进行了修正。

PV = nRT

7. Thermochemistry and Thermodynamics | 热化学与热力学

Enthalpy (H) measures heat content. ΔH = H_products – H_reactants. A negative ΔH indicates an exothermic reaction (releases heat); a positive ΔH means endothermic (absorbs heat).

焓（H）衡量热含量。ΔH = H_产物 – H_反应物。ΔH < 0 为放热反应；ΔH > 0 为吸热反应。

Hess’s Law states that the total enthalpy change for a reaction is the sum of enthalpy changes for individual steps, independent of pathway. Standard enthalpy of formation (ΔH_f°) for elements in their standard state is zero.

赫斯定律指出，总反应焓变等于各步反应焓变之和，与路径无关。标准摩尔生成焓（ΔH_f°）对于标准状态下的单质等于零。

Calorimetry: q = m c ΔT, where c is specific heat capacity. In a coffee-cup calorimeter, q_system + q_surroundings = 0.

量热法：q = m c ΔT，其中 c 为比热容。在保温杯量热计中，q_系统 + q_环境 = 0。

Entropy (S) measures disorder; gases have higher entropy than solids. Gibbs free energy predicts spontaneity: ΔG = ΔH – TΔS. A reaction is spontaneous when ΔG < 0.

熵（S）衡量混乱度；气体的熵大于固体。吉布斯自由能判断反应自发性：ΔG = ΔH – TΔS。当 ΔG < 0 时，反应自发进行。

ΔG = ΔH – TΔS

8. Chemical Kinetics | 化学动力学

Reaction rate is change in concentration per unit time. For a reaction aA + bB → products, the rate law may be: rate = k[A]^m[B]^n. The exponents m and n are the reaction orders, determined experimentally, not from coefficients.

反应速率是单位时间内浓度的变化量。对于反应 aA + bB → 产物，速率方程可能为：速率 = k[A]^m[B]^n。指数 m 和 n 为反应级数，由实验确定，而并非化学计量系数。

The rate constant k is temperature dependent. The Arrhenius equation: k = Ae^(-Ea/RT), where Ea is activation energy. Catalysts lower Ea and provide an alternative pathway, increasing rate without being consumed.

速率常数 k 随温度变化。阿伦尼乌斯方程：k = Ae^(-Ea/RT)，其中 Ea 为活化能。催化剂降低活化能、提供新的反应路径，加快速率而自身不被消耗。

Reaction mechanisms consist of elementary steps. The slowest step (rate-determining step) dictates the overall rate law. Molecularity describes the number of reacting particles in an elementary step.

反应机理由基元步骤组成。最慢的一步（决速步）决定总速率方程。分子数指基元步骤中参与反应的微粒数目。

ln(k₂/k₁) = (Ea/R)(1/T₁ – 1/T₂)

9. Chemical Equilibrium | 化学平衡

Equilibrium occurs when the forward and reverse reaction rates are equal, and concentrations remain constant. The equilibrium constant Kc = [products]ⁿ / [reactants]ᵐ, with exponents equal to coefficients in the balanced equation. Pure solids and liquids are omitted.

当正逆反应速率相等，浓度保持恒定时达成平衡。平衡常数 Kc = [产物]ⁿ / [反应物]ᵐ，指数即配平方程中的系数。纯固体和液体不写入表达式。

If Kc » 1, products are favored; if Kc « 1, reactants are favored. Kp is used for gases, with partial pressures. Kp and Kc are related by Kp = Kc(RT)^Δn, where Δn = moles of gaseous products – moles of gaseous reactants.

若 Kc » 1，平衡倾向产物；若 Kc « 1，倾向反应物。对于气体用分压平衡常数 Kp。Kp 与 Kc 的关系：Kp = Kc(RT)^Δn，Δn = 气态产物总摩尔数 – 气态反应物总摩尔数。

Le Chatelier’s Principle: if a system at equilibrium is disturbed by changing concentration, pressure, or temperature, the equilibrium shifts to counteract the disturbance. Adding reactants shifts right; increasing temperature favors endothermic direction.

勒夏特列原理：若平衡体系受到浓度、压强或温度变化的扰动，平衡会向着减弱这种改变的方向移动。增加反应物浓度平衡右移；升高温度平衡向吸热方向移动。

Reaction quotient Q has the same expression as Kc but uses current concentrations. If Q < Kc, reaction proceeds forward; if Q > Kc, reverse.

反应商 Q 表达式与 Kc 相同但代入当前浓度。若 Q < Kc，反应正向进行；若 Q > Kc，反应逆向进行。

N₂(g) + 3H₂(g) ⇌ 2NH₃(g)

10. Acids, Bases, and pH | 酸、碱与pH

Arrhenius acids produce H⁺ in water; bases produce OH⁻. Bronsted-Lowry acids are proton donors, bases are proton acceptors. Lewis acids accept an electron pair, Lewis bases donate an electron pair.

阿伦尼乌斯酸在水中产生 H⁺；碱产生 OH⁻。布朗斯特-劳里酸是质子给体，碱是质子受体。路易斯酸接受电子对，路易斯碱给予电子对。

pH = –log[H⁺]; pOH = –log[OH⁻]; pH + pOH = 14 at 25°C. Kw = [H⁺][OH⁻] = 1.0×10⁻¹⁴. Strong acids and bases dissociate completely; weak acids and bases partially dissociate, with Ka and Kb.

pH = –log[H⁺]；pOH = –log[OH⁻]；在 25°C 时 pH + pOH = 14。Kw = [H⁺][OH⁻] = 1.0×10⁻¹⁴。强酸和强碱完全电离；弱酸和弱碱部分电离，对应 Ka 和 Kb。

Buffer solutions resist pH changes and consist of a weak acid and its conjugate base or a weak base and its conjugate acid. The Henderson-Hasselbalch equation estimates pH of a buffer.

缓冲溶液能够抵抗 pH 变化，由弱酸及其共轭碱或弱碱及其共轭酸组成。亨德森-哈塞尔巴尔赫方程可用于估算缓冲溶液的 pH。

Titration curves: strong acid–strong base have equivalence point at pH 7; weak acid–strong base above 7. Indicators change color over a pH range.

滴定曲线：强酸强碱滴定的等量点在 pH 7；弱酸-强碱滴定等量点大于 7。指示剂在特定 pH 范围内变色。

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SAT2 Chemistry: Comprehensive Knowledge Summary | SAT2化学知识点总结