The electron sea reflects photons off the smooth surface. There is an upper-frequency limit to the light that can be reflected.
The strong attraction between atoms in metallic bonds makes metals strong and gives them high density, high melting point, high boiling point, and low volatility.
There are exceptions. For example, mercury is a liquid under ordinary conditions and has a high vapor pressure. In fact, all of the metals in the zinc group Zn, Cd, and Hg are relatively volatile. Because the strength of a bond depends on its participant atoms, it's difficult to rank types of chemical bonds.
Covalent, ionic, and metallic bonds may all be strong chemical bonds. Even in molten metal, bonding can be strong. Gallium, for example, is nonvolatile and has a high boiling point even though it has a low melting point. If the conditions are right, metallic bonding doesn't even require a lattice. This has been observed in glasses, which have an amorphous structure. Actively scan device characteristics for identification. Use precise geolocation data.
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Measure content performance. Develop and improve products. List of Partners vendors. Share Flipboard Email. All of the 3s orbitals on all of the atoms overlap to give a vast number of molecular orbitals that extend over the whole piece of metal.
There have to be huge numbers of molecular orbitals, of course, because any orbital can only hold two electrons. The electrons can move freely within these molecular orbitals, and so each electron becomes detached from its parent atom. The electrons are said to be delocalized. This is sometimes described as "an array of positive ions in a sea of electrons". If you are going to use this view, beware!
Is a metal made up of atoms or ions? It is made of atoms. Each positive center in the diagram represents all the rest of the atom apart from the outer electron, but that electron has not been lost - it may no longer have an attachment to a particular atom, but it's still there in the structure.
If you work through the same argument above for sodium with magnesium, you end up with stronger bonds and hence a higher melting point. Magnesium has the outer electronic structure 3s 2. Both of these electrons become delocalized, so the "sea" has twice the electron density as it does in sodium.
The remaining "ions" also have twice the charge if you are going to use this particular view of the metal bond and so there will be more attraction between "ions" and "sea".
More realistically, each magnesium atom has 12 protons in the nucleus compared with sodium's In both cases, the nucleus is screened from the delocalized electrons by the same number of inner electrons - the 10 electrons in the 1s 2 2s 2 2p 6 orbitals. So not only will there be a greater number of delocalized electrons in magnesium, but there will also be a greater attraction for them from the magnesium nuclei.
Magnesium atoms also have a slightly smaller radius than sodium atoms, and so the delocalized electrons are closer to the nuclei. Each magnesium atom also has twelve near neighbors rather than sodium's eight. Both of these factors increase the strength of the bond still further. Note: Transition metals tend to have particularly high melting points and boiling points. The reason is that they can involve the 3d electrons in the delocalization as well as the 4s.
The more electrons you can involve, the stronger the attractions tend to be. Metals have several qualities that are unique, such as the ability to conduct electricity and heat, a low ionization energy , and a low electronegativity so they will give up electrons easily to form cations.
Combining n-type and p-type semiconductors creates a system which has useful applications in modern electronics. Forward Biased p-n Junction : If the cathode of a battery is connected to the p-type semiconductor while the anode is connected to the n-type semiconductor, the system is said to be forward biased and current flows through the junction.
Reverse Biased p-n Junction : If the battery anode is connected to the p-type semiconductor and the cathode connected to the n-type semiconductor, the system is said to be reverse biased and negligible current passes.
Electronic devices and instruments, such as digital alarm clocks, mp3 players, computer processors, and the electronics in cell phones, all take advantage of semiconductor technology.
Doping provides a way to modulate the properties of semiconductors that have broad applications in daily life. Privacy Policy. Skip to main content. Liquids and Solids. Search for:. Crystals and Band Theory Bonding in Metals: The Electron Sea Model Metallic bonding may be described as the sharing of free electrons among a lattice of positively charged metal ions.
Learning Objectives Describe the electron sea model of metallic bonding. Key Takeaways Key Points Many of the unique properties of metals can be explained by metallic bonds. Metallic bonds can occur between different elements to form an alloy. In contrast to electrons that participate in both ionic and covalent bonds, electrons that participate in metallic bonds delocalize, forming a sea of electrons around the positive nuclei of metals.
Key Terms metallic bond : A chemical bond in which mobile electrons are shared over many nuclei; this leads to electrical conduction. Doping: Connectivity of Semiconductors The process of adding substances to a pure semiconductor for the purposes of modulating its electrical properties is known as doping.
Learning Objectives Examine the method of doping a pure semiconductor in order to increase its electrical conductivity. Key Takeaways Key Points Semiconductors are doped to generate either a surplus or a deficiency in valence electrons. Doping allows researchers to exploit the properties of sets of elements, referred to as dopants, in order to modulate the conductivity of a semiconductor.
There are two types of dopants, n-type dopants and p-type dopants; n-type dopants act as electron donors, and p-type dopants act as electron acceptors. Combining n-type and p-type semiconductors creates systems which have useful applications in modern electronics. Key Terms doping : The addition of small quantities of an element an impurity to a pure semiconductor to change its electrical conductivity characteristics.
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