Bonding And Elements Essay, Research Paper
Element ? a substance which cannot be broken down
into two or more substances by any means. Only contains one type of atom. Compound ? a substance in which atoms of two or
more elements have been chemically combined. Ionic
Bonding ·
Metals bonding with non-metals ·
Involves transfer of electrons from metal to
non-metal, so that both species obtain full outer shell electron configurations
(Noble gas configuration). ·
Metals lose electrons to form positive ions
(Cations). ·
Non-metals gain electrons to form negative ions
(Anions). ·
The ions are held together by strong forces of
electrostatic attraction. The ions are held in a giant three-dimensional
regular lattice. Properties 1. High
melting and boiling points ? due to strong electrostatic forces between ions. 2. Soluble
in water (polar solvent), but not in hexane ? due to the attraction of the
atoms on the water molecules for the positive and negative ions. 3. Conduct
when molten, or in solution but not when solid ? ions are free to move when molten
or in solution. Example Sodium Chloride Na [2,8,1] Cl
[2,8,7] Na+ [2,8] Cl?
[2,8,8] Covalent
Bonding ·
Between non-metals and non-metals ·
Involves the sharing of electrons. Atoms share
electrons, so that both can achieve a full outer shell electron configuration. Two forms of covalent compounds:
simple and giant. Simple covalent compounds are
usually gases, liquids or solids with relatively low melting and boiling
points. This is because the forces between the molecules are relatively weak. Simple covalent compounds do not conduct
electricity, as there is no overall electric charge on the molecules. Examples of simple covalent
compounds: methane (CH4), ammonia (NH3), hydrogen
chloride (HCl) Methane (CH?4)? electrons from carbon
represented by x, electrons form hydrogen represented by o. This line represents a covalent bond ? shared
pair of electrons. Giant covalent structures
usually have high melting and boiling points, because the covalent bonds
themselves need to be broken. Examples of giant covalent
compounds are silicon dioxide (SiO2), graphite and diamond
(allotropes of carbon). Silicon dioxide has the same structure as diamond. Structure
and properties of diamond and graphite Diamond
Graphite In Diamond each carbon is bonded to four other
carbon atoms. In Graphite each carbon is bonded to three other
carbon atoms. It conducts electricity because it has mobile electrons between
the layers Metallic Bonding ·
Found in metals, which have giant structures. ·
An array of cations surrounded by a sea of
?delocalised? (mobile) electrons. Properties 1. High
melting point and boiling points ? the atoms are packed close together and the
bonds holding them are very strong. The energy needed to melt the metals is
high. 2. Conduct
heat and electricity ? electrons in the ?sea? are mobile. A current (flow of
electrons) can pass. 3. Insoluble
in water and organic solvents, but may react with water.
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Как писать рефераты Практические рекомендации по написанию студенческих рефератов. |
| ! | План реферата Краткий список разделов, отражающий структура и порядок работы над будующим рефератом. |
| ! | Введение реферата Вводная часть работы, в которой отражается цель и обозначается список задач. |
| ! | Заключение реферата В заключении подводятся итоги, описывается была ли достигнута поставленная цель, каковы результаты. |
| ! | Оформление рефератов Методические рекомендации по грамотному оформлению работы по ГОСТ. |
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