首页 国际时事文章正文

十大网赌娱乐网址:「A*必备干货」国际课程A-level化学重点学习笔记:原子

国际时事 2022年06月22日 21:36 6 十大信誉网
十大网赌娱乐网址:

A-Level的化学是在GCSE学习阶段时关于自然、有机和无机化学的一些重要且基本的概念上展开的,并为将来学生选择学习更高阶的化学,或化学专业里的一些特殊领域做深入研究的学生打下基础。

虽然A-level考试中化学的难度比较大,但我们只要、掌握好学习方法,及时总结归纳,把握每章的重点内容,把基础知识打扎实,一定会取得好成绩。今天我们来分享学习A-level的化学课程中比较基础的一节内容:原子的结构 The Structure of the Atom

「A*必备干货」国际课程A-level化学重点学习笔记:原子的结构

The nucleus 原子核

「A*必备干货」国际课程A-level化学重点学习笔记:原子的结构

The protons and neutrons in each atom are tightly packed in a positively charged nucleus. Negatively charged electrons move around the nucleus. The number of protons in a nucleus defines the type of atom and is the same as the atomic number. The number of neutrons is found by subtracting the atomic number from the mass number. In an atom because there is no overall charge the number of electrons equals the number of protons.

每个原子中的质子和中子都紧紧地挤在一个带正电的原子核中。带负电的电子在原子核周围移动。原子核中的质子数决定了原子的类型,与原子数相同。中子的数量是通过从质量数中减去原子数而得到的。在一个原子中,由于没有整体电荷,电子数等于质子数。

In chemical reactions, the nucleus remains unchanged.

在化学反应中,原子核保持不变。

Geiger and Marsden bombarded a thin gold foil with a beam of alpha particles.

Most of the particles passed through the foil without deflection and were detected by a flash of light when the alpha particle struck a zinc sulphide screen, surrounding the gold foil.

A few were deflected and some of these were deflected at angles greater than 900, suggesting they had been repelled by large positive charges within the foil - nuclei of atoms of gold.

盖格和马斯登用一束α粒子轰击薄薄的金箔。

大多数粒子在没有偏转的情况下通过了金箔,并在α粒子击中金箔周围的硫化锌屏幕时被一道闪光检测到。

少数粒子被偏转,其中一些被偏转的角度大于900,这表明它们被金箔内的大型正电荷--金原子核--所排斥。

「A*必备干货」国际课程A-level化学重点学习笔记:原子的结构

Arrangement of electrons around the nucleus 电子围绕原子核的排列方式

From GCSE you should be familiar with the Bohr model of electrons arranged around a nucleus. The electrons are in certain energy levels and each energy level can hold only up to a maximum number of electrons.

从GCSE开始,你应该熟悉电子围绕原子核排列的玻尔模型。电子处于一定的能级,每个能级只能容纳最多的电子数。

This is summarised in the table below:

Energy level or 'shell'

Max no of electrons

1st

2

2nd

8

3rd

18

4th

32

5th

50

A sodium atom containing 11 electrons has an electron arrangement of 2,8,1. Two electrons filling the first shell, eight electrons filling the second shell and one electron in the outer third shell.

一个含有11个电子的钠原子的电子排列是2,8,1。两个电子填充第一层外壳,八个电子填充第二层外壳,一个电子在外面的第三层外壳。

「A*必备干货」国际课程A-level化学重点学习笔记:原子的结构

However, these models of electron arrangement are simple and a more advance done can now be used. It is possible to break these energy levels into sub-shells.

Electrons are impossible to locate exactly at any one time. It is however, possible to indicate a region or volume where the electron is most likely to be found. This region is called an Orbital.

Each orbital is capable of holding a maximum of 2 electrons. Orbitals can be divided into s, p, d, and f types. Each type has its own characteristic shape.

然而,这些电子排列的模型是简单的,现在可以使用一个更先进的完成。有可能将这些能级分解成子壳。

电子在任何时候都不可能被准确定位。然而,有可能指出电子最有可能被找到的一个区域或体积。这个区域被称为 "轨道"。

每个轨道最多能够容纳2个电子。轨道可以分为s、p、d和f类型。每种类型都有自己的特征形状。

The shape of s and p orbitals are shown below:

「A*必备干货」国际课程A-level化学重点学习笔记:原子的结构

The first energy level holds a maximum of 2 electrons in one s type orbital called 1s. There are no p, d, or f orbitals available at this energy level.

The second energy level consists of one s type orbital and three p type orbitals: 2s, 2px, 2py, 2pz.

Note: there are 3 p orbitals of identical energy, one along the x axis, one along the y-axis and one along the z-axis.

These four orbitals can hold a total of 8 electrons (i.e. 2 electrons each). There are no 2d or 2f orbitals.

The third energy level consists of: one s type orbital, three p type orbitals and 5 d type orbitals. These nine orbitals can hold a maximum of 18 electrons altogether (i.e. two electrons each).

Note: there are seven f type orbitals holding a maximum of 14 electrons in total.

第一能级在一个称为1s的s型轨道上最多容纳2个电子。在这个能级上没有p、d或f轨道可用。

第二个能级由一个s型轨道和三个p型轨道组成:2S、2px、2py、2PZ。

注意:有3个能量相同的p型轨道,一个沿x轴,一个沿y轴,一个沿z轴。

这四个轨道总共可以容纳8个电子(即每个2个电子)。没有2d或2f轨道。

第三能级包括:一个s型轨道,三个p型轨道和五个d型轨道。这9个轨道最多可以容纳18个电子(即每个电子两个)。

注意:有7个f型轨道,总共最多可容纳14个电子。

「A*必备干货」国际课程A-level化学重点学习笔记:原子的结构

When filling the available orbitals with electrons two important principles should be followed:

1. Electrons fill the lowest energy orbitals first and the other orbitals in order of ascending energy. It is incorrect to assume that an energy level is always completely filled before electrons enter the next energy level. The order of filling orbitals as shown below is 1s, 2s, 2p, 3s, 3p, 4s, 3d, 4p, 5s, 4d, 5p, 6s, 4f, 5d, 6p.

2. Where there are several orbitals of exactly the same energy e.g. three 2p orbitals, electrons will occupy different orbitals whenever possible.

For example: nitrogen is 1s2 2s2 2px1 2py1 2pz1 and not 1s2 2s2 2px2 2py1.

当用电子填充可用的轨道时,应遵循两个重要原则

1. 电子首先填充能量最低的轨道,其他轨道按能量递增的顺序填充。假设一个能级在电子进入下一个能级之前总是被完全填充,这是不正确的。如下图所示,填充轨道的顺序是:1s, 2s, 2p, 3s, 3p, 4s, 3d, 4p, 5s, 4d, 5p, 6s, 4f, 5d, 6p。

2. 如果有几个能量完全相同的轨道,例如三个2p轨道,电子将尽可能占据不同的轨道。

例如:氮是1s2 2s2 2px1 2py1 2pz1而不是1s2 2s2 2px2 2py1。

「A*必备干货」国际课程A-level化学重点学习笔记:原子的结构

This principle is Hund's rule. When an orbital only contains 1 electron then this electron is said to be unpaired.

a) The small number above the orbital refers to the number of electrons in the orbital: 1s2 means 2 electrons in a 1s orbital.

b) The electron arrangements are sometimes abbreviated.

For example: the electron arrangement for calcium may be written as 1s2 2s2 2p6 3s2 3p6 4s2.

这个原则就是洪德定则。当一个轨道只包含1个电子时,那么这个电子被说成是未配对的。

a) 轨道上方的小数字是指轨道中的电子数:1s2意味着1s轨道中有2个电子。

b) 电子排列有时被缩写。

例如:钙的电子排列可以写成1s2 2s2 2p6 3s2 3p6 4s2。

亚洲十大信誉平台-十大信誉网赌网站【官方直营】Copyright @ 亚洲十大信誉平台-十大信誉网赌网站【官方直营】(天津)有限公司 All Rights Reserved.