📚 Year 10 WJEC Chemistry: High-Frequency Topics & Common Mistakes Analysis | WJEC十年级化学：高频考点与易错题分析
Mastering Year 10 WJEC Chemistry means not only knowing the facts but also understanding where marks are frequently lost. From atomic structure to organic chemistry, certain topics appear every year, and the same misconceptions trip up students time and again. This revision guide highlights these high-frequency topics, explains common errors, and shows you how to avoid them.
掌握十年级WJEC化学不仅需要记住知识点，更要了解哪些地方经常丢分。从原子结构到有机化学，一些主题每年必考，而且同样的误解一次次让学生出错。本复习指南聚焦高频考点，分析常见错误，并告诉你如何避开这些陷阱。
1. Atomic Structure & Periodic Table | 原子结构与周期表
WJEC requires you to determine subatomic particles from atomic (proton) number and mass number. You must also draw electronic configurations (e.g., 2,8,8,2 for calcium) and link an element's outer electron count to its Group number.
WJEC要求你能够根据原子序数和质量数确定亚原子粒子数。你还需要画出电子排布（如钙的2,8,8,2），并将元素的最外层电子数与族序数关联起来。
A common error is confusing mass number and relative atomic mass. The mass number is the total of protons and neutrons in one specific atom, while relative atomic mass (Ar) is the weighted mean of all isotopes taking abundance into account.
常见错误是混淆质量数与相对原子质量。质量数是某一个原子中的质子和中子总数，而相对原子质量（Ar）是考虑所有同位素丰度后的加权平均值。
Another pitfall is writing electronic configurations for ions incorrectly. For instance, Na⁺ is 2,8 (not 2,8,1), and O²⁻ is 2,8 (not 2,6).
另一个易错点是写错离子的电子排布。例如Na⁺是2,8（不是2,8,1），O²⁻是2,8（不是2,6）。
students often forget to divide by 100 or use the wrong average. Practice: Ar = [(mass₁ × %₁) + (mass₂ × % c number, not mass number; the use of relative atomic mass accounts for isotopic mixtures.
在根据同位素丰度计算Ar时，学生常常忘记除以100或使用了错误的平均值。请练习公式：Ar = [(质量₁ × 丰度₁) + (质量₂ × 丰度₂)] / 100。此外，周期表是按原子序数递增排列的，而不是按质量数；相对原子质量的使用考虑到了同位素混合物。
2. Ionic Bonding and Chemical Formulae | 离子键与化学式
Ionic bonding involves the transfer of electrons from a metal to a non-metal, forming oppositely charged ions held by strong electrostatic forces. You must be able to draw dot-and-cross
Published by TutorHao | Year 10 Chemistry Revision Series | aleveler.com
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