1. What are Metals? 2. Why metals conduct electricity? 3. What are the properties of metals?
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Metallic bond is the reaction between molecules within metals called alkali reactive force. It is the sharing of a sea of delocalised electrons amongst a lattice of positive ions, where the electrons act as a "glue" giving the substance a definite structure. The electrons and the positive ions in the metal have a strong attractive force between them. Therefore metals often have high melting or boiling points. The principle is similar to that of ionic bonds . The metallic bond accounts for many physical characteristics of metals, such as strength , malleability , ductility , luster , conduction of heat and electricity . Because the electrons move independently of the positive ions in a sea of negative charge, the metal gains some electrical conductivity. It allows the energy to pass quickly through the electrons generating a current . Heat conduction works on the same principle - the free electrons can transfer the energy at a faster rate than other substanc...
Metallic bonding constitutes the electrostatic attractive forces between the delocalized electrons , called conduction electrons , gathered in an electron cloud and the positively charged metal ions. Understood as the sharing of "free" electrons among a lattice of positively charged ions ( cations ), metallic bonding is sometimes compared with that of molten salts ; however, this simplistic view [ which? ] holds true for very few [ which? ] metals . In a more quantum-mechanical view, the conduction electrons divide their density equally over all atoms that function as neutral (non-charged) entities. [ citation needed ] Metallic bonding accounts for many physical properties of metals, such as strength , ductility , thermal and electrical conductivity , opacity , and luster . [ 1 ] [ 2 ] [ 3 ] [ 4 ] Although the term "metallic bond" is often used in contrast to the term " covalent bond ", it is preferable [ by whom? ] to use the term metallic bon...
Phosphorus(V) chloride, PCl 5 In the case of phosphorus, 5 covalent bonds are possible - as in PCl 5 . Phosphorus forms two chlorides - PCl 3 and PCl 5 . When phosphorus burns in chlorine both are formed - the majority product depending on how much chlorine is available. We've already looked at the structure of PCl 3 . The diagram of PCl 5 (like the previous diagram of PCl 3 ) shows only the outer electrons. Notice that the phosphorus now has 5 pairs of electrons in the outer level - certainly not a noble gas structure. You would have been content to draw PCl 3 at GCSE, but PCl 5 would have looked very worrying. Why does phosphorus sometimes break away from a noble gas structure and form five bonds? In order to answer that question, we need to explore territory beyond the limits of most current A'level syllabuses. Don't be put off by this! It isn't particularly difficult, and is extremely useful if you are going to understand th...
Boron trifluoride, BF 3 A boron atom only has 3 electrons in its outer level, and there is no possibility of it reaching a noble gas structure by simple sharing of electrons. Is this a problem? No. The boron has formed the maximum number of bonds that it can in the circumstances, and this is a perfectly valid structure. Energy is released whenever a covalent bond is formed. Because energy is being lost from the system, it becomes more stable after every covalent bond is made. It follows, therefore, that an atom will tend to make as many covalent bonds as possible. In the case of boron in BF 3 , three bonds is the maximum possible because boron only has 3 electrons to share
Hydrogen chloride The hydrogen has a helium structure, and the chlorine an argon structure. Covalent bonding at A'level Cases where there isn't any difference from the simple view If you stick closely to modern A'level syllabuses, there is little need to move far from the simple (GCSE) view. The only thing which must be changed is the over-reliance on the concept of noble gas structures. Most of the simple molecules you draw do in fact have all their atoms with noble gas structures. For example: Even with a more complicated molecule like PCl 3 , there's no problem. In this case, only the outer electrons are shown for simplicity. Each atom in this structure has inner layers of electrons of 2,8. Again, everything present has a noble gas structure. Cases where the simple view throws up problems
Some very simple covalent molecules Chlorine For example, two chlorine atoms could both achieve stable structures by sharing their single unpaired electron as in the diagram. The fact that one chlorine has been drawn with electrons marked as crosses and the other as dots is simply to show where all the electrons come from. In reality there is no difference between them. The two chlorine atoms are said to be joined by a covalent bond. The reason that the two chlorine atoms stick together is that the shared pair of electrons is attracted to the nucleus of both chlorine atoms. Hydrogen Hydrogen atoms only need two electrons in their outer level to reach the noble gas structure of helium . Once again, the covalent bond holds the two atoms together because the pair of electrons is attracted to both nuclei.
A covalent bond is a chemical bond that involves the sharing of electron pairs between atoms . The stable balance of attractive and repulsive forces between atoms when they share electrons is known as covalent bonding. [ 1 ] For many molecules, the sharing of electrons allows each atom to attain the equivalent of a full outer shell, corresponding to a stable electronic configuration. Covalent bonding includes many kinds of interactions, including σ-bonding , π-bonding , metal-to-metal bonding, agostic interactions , and three-center two-electron bonds . [ 2 ] [ 3 ] The term covalent bond dates from 1939. [ 4 ] The prefix co- means jointly, associated in action, partnered to a lesser degree, etc.; thus a "co-valent bond", in essence, means that the atoms share " valence ", such as is discussed in valence bond theory . In the molecule H 2 , the hydrogen atoms share the two electrons via covalent bonding. [ 5 ] Covalency is greatest between atoms of si...
THE A'LEVEL VIEW OF IONIC BONDING Electrons are transferred from one atom to another resulting in the formation of positive and negative ions. The electrostatic attractions between the positive and negative ions hold the compound together. So what's new? At heart - nothing. What needs modifying is the view that there is something magic about noble gas structures. There are far more ions which don't have noble gas structures than there are which do. Some common ions which don't have noble gas structures You may have come across some of the following ions in a basic course like GCSE. They are all perfectly stable , but not one of them has a noble gas structure. Fe 3+ [Ar]3d 5 Cu 2+ [Ar]3d 9 Zn 2+ [Ar]3d 10 Ag + [Kr]4d 10 Pb 2+ [Xe]4f 14 5d 10 6s 2 Noble gases (apart from helium ) have an outer electronic structure ns 2 np 6 .
Some other examples of ionic bonding magnesium oxide Again, noble gas structures are formed, and the magnesium oxide is held together by very strong attractions between the ions. The ionic bonding is stronger than in sodium chloride because this time you have 2+ ions attracting 2- ions. The greater the charge, the greater the attraction. The formula of magnesium oxide is MgO. calcium chloride This time you need two chlorines to use up the two outer electrons in the calcium. The formula of calcium chloride is therefore CaCl 2 . potassium oxide Again, noble gas structures are formed. It takes two potassiums to supply the electrons the oxygen needs. The formula of potassium oxide is K 2 O.
Ionic bonding in sodium chloride Sodium (2,8,1) has 1 electron more than a stable noble gas structure (2,8). If it gave away that electron it would become more stable. Chlorine (2,8,7) has 1 electron short of a stable noble gas structure (2,8,8). If it could gain an electron from somewhere it too would become more stable. The answer is obvious . If a sodium atom gives an electron to a chlorine atom, both become more stable. The sodium has lost an electron, so it no longer has equal numbers of electrons and protons. Because it has one more proton than electron, it has a charge of 1+. If electrons are lost from an atom, positive ions are formed . Positive ions are sometimes called cations. The chlorine has gained an electron, so it now has one more electron than proton . It therefore has a charge of 1-. If electrons are gained by an atom, negative ions are formed. A negative ion is sometimes called an anion. The nature of the bond The sodiu...
A chemical bond is an attraction between atoms that allows the formation of chemical substances that contain two or more atoms. The bond is caused by the electrostatic force of attraction between opposite charges, either between electrons and nuclei , or as the result of a dipole attraction. The strength of chemical bonds varies considerably; there are "strong bonds" such as covalent or ionic bonds and "weak bonds" such as dipole–dipole interactions , the London dispersion force and hydrogen bonding .