GCSE OCR Chemistry: Atomic Structure Key Points | GCSE OCR 化学：原子结构 考点精讲

📚 GCSE OCR Chemistry: Atomic Structure Key Points | GCSE OCR 化学：原子结构 考点精讲

Atomic structure is the foundation of chemistry. Understanding how atoms are built explains everything from chemical bonding to the properties of materials. In the OCR GCSE Chemistry course, you need to describe the fundamental particles, use atomic numbers and mass numbers, calculate relative atomic masses, write electronic configurations, and explain how ions form.

原子结构是化学的基础。理解原子的构成能够解释从化学键合到物质性质的一切。在 OCR GCSE 化学课程中，你需要描述基本粒子，使用原子序数和质量数，计算相对原子质量，书写电子排布，并解释离子是如何形成的。

1. The Composition of an Atom | 原子的组成

All matter is made up of atoms. Each atom consists of a central nucleus containing protons and neutrons, surrounded by electrons moving in shells (energy levels).

所有物质均由原子构成。每个原子由一个包含质子和中子的中心原子核，以及在电子层（能级）中运动的电子所组成。

Most of the mass of the atom is concentrated in the nucleus. The electrons have very little mass, but they occupy most of the volume.

原子的大部分质量集中在原子核里。电子的质量极小，但它们占据了原子的大部分体积。

The nucleus is incredibly small compared with the overall size of the atom. If the atom were the size of a sports stadium, the nucleus would be the size of a pea at the centre.

与原子整体大小相比，原子核极其微小。如果将原子比作一个体育场，原子核就是中心的一粒豌豆大小。

2. Subatomic Particles at a Glance | 亚原子粒子一览

There are three key subatomic particles you must know: protons, neutrons and electrons. Their properties are summarised in the table below.

你必须知道的三种亚原子粒子是：质子、中子和电子。下表总结了它们的性质。

Protons and neutrons have roughly the same mass, whereas electrons are almost massless. The charges on the proton and electron are equal but opposite, so a neutral atom has equal numbers of protons and electrons.

质子和中子质量大致相同，而电子几乎没有质量。质子和电子所带电荷量相等但符号相反，因此中性原子的质子数和电子数相等。

3. Atomic Number and Mass Number | 原子序数与质量数

Every element is defined by its atomic (proton) number, Z. The atomic number tells you the number of protons in the nucleus of an atom. For a neutral atom, it also equals the number of electrons.

每一种元素都由其原子序数（质子数）Z 定义。原子序数告诉了你原子核内质子的数量。对于中性原子，它也等于电子数。

The mass (nucleon) number, A, is the total number of protons plus neutrons in the nucleus. It is always a whole number.

质量数（核子数）A 是原子核中质子数与中子数之和。它总是整数。

Mass number (A) = number of protons + number of neutrons

质量数 (A) = 质子数 + 中子数

For example, a carbon atom with 6 protons and 6 neutrons has atomic number 6 and mass number 12. This is often written as ¹²C (or carbon-12).

例如，一个含有6个质子和6个中子的碳原子，原子序数为6，质量数为12。通常写作 ¹²C（或碳-12）。

4. Isotopes: Same Element, Different Neutrons | 同位素：相同元素，不同的中子数

Isotopes are atoms of the same element that have the same number of protons but a different number of neutrons. This means they have the same atomic number but different mass numbers.

同位素是同种元素的不同原子，它们具有相同的质子数，但中子数不同。这意味着它们有相同的原子序数，但质量数不同。

For example, chlorine has two stable isotopes: ³⁵Cl (17 protons, 18 neutrons) and ³⁷Cl (17 protons, 20 neutrons). Both have 17 protons, so they are still chlorine, but their physical properties such as density may differ slightly.

例如，氯有两种稳定同位素：³⁵Cl（17个质子，18个中子）和 ³⁷Cl（17个质子，20个中子）。两者都有17个质子，因此它们仍然是氯，但它们的物理性质（如密度）可能略有不同。

Chemical properties of isotopes are identical because chemical reactions involve electrons, and the number of electrons is the same.

同位素的化学性质完全相同，因为化学反应涉及电子，而它们的电子数相同。

Some isotopes are radioactive (radioisotopes) because the nucleus is unstable. OCR expects you to recognise that carbon-14 is used in radiocarbon dating.

有些同位素具有放射性（放射性同位素），因为其原子核不稳定。OCR 考试要求你认识到碳-14 被用于放射性碳定年法。

Published by TutorHao | GCSE Chemistry Revision Series | aleveler.com

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