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元素周期表和有机元素
Elements are the smallest units of matter that cannot be broken down further by chemical processes. There are 118 known elements, but not all of…
原子结构
All matter is composed of atoms, the smallest individual units of elements. Each atom is made up of three subatomic particles: protons, neutrons,…
电子行为
Electrons are negatively charged subatomic particles that are attracted to an orbit around the positively-charged nucleus of an atom. They reside…
电子轨道模型
Orbitals are the areas outside of the atomic nucleus where electrons are most likely to reside. They are characterized by different energy levels,…
分子和化合物
An atom is most stable when its valence shell—the outermost energy shell that contains electrons—is full. Most elements do not…
分子形状
The shape of a molecule contributes to its function and its interactions with other molecules. Over the years, many different models have been…
碳骨架
The backbone of all organic compounds is a carbon skeleton. Each carbon atom can make four bonds, and as the carbon skeleton increases in length,…
化学反应
A chemical reaction is a process by which the bonds in the atoms of substances are rearranged to generate new substances. Matter cannot be created…
同位素
Elements have a set number of protons that determines their atomic number. For example, all atoms with eight protons are oxygen. However, the number…
共价键
When two atoms share electrons to complete their valence shells they create a covalent bond. An atom’s electronegativity—the force with…
离子键
When atoms gain or lose electrons to achieve a more stable electron configuration they form ions. Ionic bonds are electrostatic attractions between…
氢键
Hydrogen bonds are weak attractions between atoms that have formed other chemical bonds. One of these atoms is electronegative, like oxygen, and has…
范德瓦尔力
Van der Waal interactions are nonspecific attractions created when one atom comes close enough to another one to disturb its electrons—inducing…
水的状态
Water exists in three main states: solid (ice), liquid, and gas (steam). The state water is in depends on the intermolecular forces that draw water…
酸碱性
The potential for a solution to donate or accept hydrogen ions determines whether it is an acid or a base. Acidic solutions donate protons, whereas…
溶剂
A solvent is a substance, most often a liquid, that can dissolve other substances. Here, the substance being dissolved is called a solute. When a…
氧化还原反应
Oxidation-reduction, or redox, reactions change the oxidation states of atoms via the transfer of electrons from one atom, the reducing agent, to…
黏附
Adhesion occurs when one type of molecule is attracted to a different kind of molecule. Water exhibits adhesive properties in the presence of polar…
内聚力
Cohesion is the attraction between molecules of the same type - such as water molecules. The partially charged negative oxygen of one water molecule…
比热容
A substance’s specific heat capacity refers to the amount of energy required to heat one gram of the substance by one degree. Water has a high…
汽化
Vaporization changes a liquid substance into a gaseous or vaporous substance. To achieve this, kinetic energy must be greater than the intermolecular…
降血脂药物对胆固醇颗粒形态的差异化作用
Treatment of dyslipidemia patients with lipid-lowering drugs leads to a significant reduction in low-density lipoproteins (LDL) level and a low to…
胆固醇外流检测
Cholesterol content of cells must be maintained within the very tight limits, too much or too little cholesterol in a cell results in disruption of…
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