Copper

Copper — page 3 — Chapter Onee The Element Copper The element copper is a familiar part of life in the developed world Copper's chemical symbol Cu comes from the Latin word cyprium which was later shortened to cuprum meaning from the island of Cyprus Copper found in its pure state in nature called native copper has been known since ancient times Tools made of copper alloys mixtures of copper with other elements have been used since the beginning of the Bronze Age around 4000 BC In its pure form copper is used in electrical wire plumbing pipe and jewelry Pure copper is a shiny metal with a red-orange color The surface of pure copper tarnishes very slowly when exposed to air and water but this thin green or brown patina does not crumble like rusty iron A patina is a film that forms nat(cid:173) urally on copper or its alloys as a result of oxidation Copper is a relatively soft metal that can be bent beaten or cast into useful shapes It is even more useful when it is combined with other elements usually tin or zinc to make bronze or brass alloys Bronze and brass are used to make many tools screws and other hardware that resist corrosion or decay Atoms Elements and Compounds Everything you can see in the world and nearly everything in the universe is made up of elements Some objects are pure with one kind

Copper — page 4 — The Element Coppe of element only Some are compounds with different elements bonded chemically sticking together as if they were glued together in different arrangements and with glues of different strengths How small a piece can you have of an object If you started with a trumpet you could see that it has some brass metal parts and some steel parts The smallest piece of brass you could cut would have copper and zinc which were originally melted together at a high temperature You could use chemical reactions to separate out the copper The smallest por(cid:173) tion that you can have of an element is called an atom which is far too small to see with the microscope you might use in school Atoms of cop(cid:173) per are so tiny that about thirty-five million of them side by side would make a line only 0 4 inch 1 centimeter long One atom would be the smallest piece of copper you could ever have Inside that atom are even smaller pieces called subatomic particles Inside the Atom Atoms are made of three main kinds of subatomic particles At the center of the atom the nucleus is a dense core of protons which carry a posi(cid:173) tive electrical charge and neutrons which have no charge The nucleus is a small part of the atom it's like a marble in the center of a football stadium But the nucleus contains nearly all the mass of the atom Copper has twenty-nine protons in its nucleus That is how the element is identi(cid:173) fied Any atom anywhere in the universe with twenty-nine protons in its nucleus is an atom of the element copper Around the atom's nucleus the electrons occupy overlapping layers called shells Electrons have a negative electrical charge and are attracted to the protons in the nucleus The negative and positive elec(cid:173) trical charges of the atom are balanced and the number of electrons and protons are equal An atom of copper has twenty-nine protons and twenty-nine electrons 7

Copper — page 5 — Copper All atoms are made up of the subatomic particles protons neutrons and elec(cid:173) trons The protons and neutrons cling together in the nucleus The electrons circle the nucleus in layers called shells It's easier to look at a drawing of an atom like this one with the electrons shown close to the nucleus but a more realis(cid:173) tic model would have tiny electrons whizzing around a stadium with a raspberry at the center for the nucleus In metals the outermost electrons are less tightly held to the nucleus than the inner electrons These outer electrons are called valence electrons They can be readily exchanged with neighboring atoms so that electrons move from one atom to the next This flow of electrons is what enables met(cid:173) als to conduct heat and electricity When an atom of metal gives up one or more of its valence electrons to an atom of nonmetal both of these atoms become charged particles called ions The metal ion is called a cation It has a positive charge because it has lost one or more electrons The Periodic Table Some elements such as copper gold iron and mercury have been known since ancient times As elements have been discovered and stud(cid:173) ied over the years scientists have organized this knowledge Elements are 8

Copper — page 6 — The Element Copper A solution of copper sulfate CuS04 and water can be used to investigate how elements can be released from compounds and electroplated When water is added to the copper sulfate the copper sulfate is broken into copper ions and sulfate ions The copper ions look for a negatively charged ion with which to combine By using a battery source and a copper Cu strip that is connected to the anode and a zinc Zn strip that is connected to the cathode and the other ends of both strips placed into the solution the electroplating experiment can be speeded up Eventually eventually some of the copper from the solution will plate onto the copper strip 9

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