Physical Properties of Transition Elements | 过渡元素的物理性质

📚 Physical Properties of Transition Elements | 过渡元素的物理性质

Transition elements, located in the d-block of the periodic table, are often described as typical metals. Their physical properties, such as high density, high melting point, good electrical conductivity and strong magnetism, make them essential in construction, electronics and engineering. This article explores these properties from a physical perspective, linking them to the underlying metallic bonding and electronic structure.

过渡元素位于周期表 d 区，常被称为典型金属。它们具有高密度、高熔点、良好导电性和强磁性等物理性质，因此在建筑、电子和工程领域不可或缺。本文从物理角度探讨这些性质，并将其与金属键和电子结构联系起来。

1. Definition and Position in the Periodic Table | 过渡元素的定义与周期表位置

Transition elements occupy the central block of the periodic table, between Groups 2 and 13. In A-level terms, a transition element is a d-block element that forms at least one stable ion with an incomplete d subshell. Although this definition is chemical, it explains why these atoms have unusual physical behaviour: the presence of inner d electrons affects the way atoms pack and bond.

过渡元素占据周期表中部，位于第2族和第13族之间。在A-level定义中，过渡元素是能形成至少一种稳定离子且d亚层未填满的d区元素。尽管这一定义偏向化学，但它解释了这些原子为何具有特殊的物理行为：内层d电子的存在影响了原子的堆积和成键方式。

For example, scandium and zinc are d-block elements but are not always classified as transition elements under the strict definition because their common ions do not have partially filled d orbitals. Nevertheless, they are often studied alongside true transition elements because they share many metallic physical properties.

例如，钪和锌属于d区元素，但按照严格定义并不总被归为过渡元素，因为它们的常见离子不具有部分填充的d轨道。然而，由于它们与真正的过渡元素有许多共同的金属物理性质，因此通常也被放在一起研究。

2. Metallic Bonding and d-Electron Contribution | 金属键与d电子的贡献

In transition metals, the outermost s electrons form a sea of delocalised electrons. In addition, some inner d electrons can also participate in metallic bonding, especially in the early transition series. This higher number of bonding electrons increases the electrostatic attraction between positive metal ions and the electron sea.

在过渡金属中，最外层s电子形成离域电子海。此外，部分内层d电子也能参与金属键，尤其是在早期过渡系中。这种更多的成键电子增强了正金属离子与电子海之间的静电吸引。

The result is a stronger metallic bond than that found in s-block metals such as sodium or magnesium. Stronger bonding requires more energy to separate atoms, which directly explains the high melting points, boiling points and densities of transition elements.

结果就是过渡金属的金属键比钠、镁等s区金属更强。更强的键需要更多能量才能将原子分开，这直接解释了过渡元素的高熔点、高沸点和高密度。

3. Atomic Radius and Density | 原子半径与密度

Transition metal atoms are relatively small for their period because the nuclear charge increases across the d-block while the added d electrons only partially shield the outer s electrons. This leads to a higher effective nuclear charge and a relatively small atomic radius.

过渡金属原子在其周期中相对较小，因为跨d区时核电荷增加，而新增的d电子对最外层s电子的屏蔽作用不完整。这导致有效核电荷较高，原子半径相对较小。

Small atomic radius combined with high atomic mass gives transition elements much higher densities than s-block metals. For example, iron has a density of about 7.9 g cm⁻³, copper about 8.9 g cm⁻³ and tungsten about 19.3 g cm⁻³, whereas sodium is only 0.97 g cm⁻³.

较小的原子半径加上较高的原子质量，使过渡元素的密度远高于s区金属。例如，铁的密度约为7.9 g cm⁻³，铜约为8.9 g cm⁻³，钨约为19.3 g cm⁻³，而钠仅为0.97 g cm⁻³。

4. Melting and Boiling Points | 熔点与沸点

Transition metals generally have very high melting and boiling points. This is a direct consequence of the strong metallic bonding arising from the involvement of both s and d electrons in the delocalised electron sea.

过渡金属通常具有非常高的熔点和沸点。这是s电子和d电子共同参与离域电子海而形成强金属键的直接结果。

Tungsten, with the highest melting point among metals at about 3422 °C, is used for light bulb filaments. Chromium, molybdenum and platinum also show exceptionally high melting temperatures, making them suitable for high-temperature applications such as furnace components and jet engines.

钨的熔点约为3422 °C，是金属中最高的，因此用于灯泡灯丝。铬、钼和铂也具有极高的熔点，使其适用于熔炉部件和喷气

Published by TutorHao | A-Level Physics Revision Series | aleveler.com

更多咨询请联系16621398022（同微信）