化学讲义
- 格式：docx
- 大小：17.40 KB
- 文档页数：3
`化学讲义
The history of atom
这些只是概念，我们不会在课堂上细讲，但是我们会把它放在作业里，并且会提醒你们应该看些什么
1. 5 physicists ：Democritus Lavoisier J. Proust Dalton J.J. Thompson
What they discovered in the history of atoms
2. 2 experiments: Cathode ray tube electrons
Gold foil nucleus and protons
实验的具体步骤你们可以自行复习，我们也会在作业中涉及一点
模型：葡萄干模型卢瑟福模型波尔模型电子云模型
3.Atomic structure
只是很简单的计算
Atomic number mass number amu isotope.
Electron configuration
我们是由emission spectrum开始讨论的
The spectrum of light released from excited atoms of an element(lights)
Ground state-electron occupies the lowest energy level.
Differences in energy are due electrons falling from a higher to lower energy levels.
So we came up with the idea of principal energy levels. The electrons in the outmost principal levels are called valence electrons, valence electrons determine the chemical properties of substances.
Now we have two ways to represent the electrons distribution of an element.
Lewis Dot diagrams: 先在四周画一个电子，第五个开始才配对：shows the valence electron of any element
Electron configuration for principal energy levels: 有2个要点：2n平方以及最外层小于等于8
举几个例子题目给他们做
海森堡不确定原理
一个微观粒子的某些物理量（如位置和动量，或方位角与动量矩，还有时间和能量等），不可能同时具有确定的数值，其中一个量越确定，另一个量的不确定程度就越大
So the electrons can be distributed in a smaller scale.
Orbitals and sublevels.
Sublevels-divisions within a principal energy level SPDF
Different shape and size
The region of space where there is the significant probability of finding a particular electron SPDF
Orbitials have the same name as their sublevel
Each can hold a maximum of 2 electrons
接下来就可以具体的分解energy levels
新的一种electron configuration
举几个例子
简便的写法:octet rules of noble gas, then write the newer energy levels so we can use the base to describe the previous electrons distribution. More convenient.
Periodic table
Period: go across the table
Group: go down the table
Naming: group 1 to 8, metals, transition metals, metalloid, nonmetals
Actanides and lanthinide
这些基础的元素周期表性质大家也都会了，接下来我们主要由三个方面来讲具体的性质。
Radius reactivity electrnegativity
Radius里我们会讨论原子和离子的大小，比较不同原子或者离子的大小并且进行比较。
从最基础的原子来看，go down the group, radius增大因为多了一层principal energy
Go across the period, radius变小，在同一energy levels 上，but the attractive forces from the nucleus (protons, positive attraction) are becoming larger, so the nucleus attracts the electrons closer, the radius decrease.
接下来我们看离子。
在元素周期表左半边的元素变成离子后，lose 1~3 electrons so that the valence electrons are at the lower energy levels, while for the 右半边的元素，gain electrons so the valence electrons are at the higher energy levels,
Although the ions have the same electron configuration, nuclear charge increases from left to right, resulting in a stronger attraction for electrons and smaller size.
举几个例子比较原子和原子，离子和离子以及原子和离子
Reactivity: for the left metal, the most reactive is the one that has the least attraction for electron because they lose electrons. 越容易丢失电子越活泼，从上到下越来越活泼，半径越大越活泼
For the right elements, 因为他们是得到电子，所以attraction forces越强越活泼，（从上到下越来越不活泼，半径越大越不活泼）
最后我就想讲electronegativity，when 2 atoms make a bond, each pulls the electrons, EN is how strongly the atom pulls the electrons. A periodic property
There are several rules to determine how the EN change
1.As go down a group, radius increases, distance from nucleus to valence electrons
increase, so attractive forces decreases, EN decrease
2.Shielding or block effect. As there are more energy levels between nucleus and valence
electrons, the block of the attractive forces become stronger, EN decrease
3.In one period, the shielding doesn’t change. But since the radius decreases, attractive
forces increases, the EN increases.
Using EN of elements, we can determine the types of bonds that it forms with elements. Group2 还是3会细讲chemical bonding ，所以我们就不讲bonding 的分类了。
我们只是介绍trend in the period table.
Make sure to make fully use of the periodic table, it’s our best friend.。
