What determines a materials physical, chemical and mechanical properties?

Atoms Electrons Neutrons Protons An atom is the smallest particle of an element that has the chemical properties of the element. Negatively charged particle. Neutral particle Positively charged particle

Elements Substances that cannot be broken down into other substances. Include metals and non-metals. Elements are composed of only 1 kind of atom.

Reading the Periodic Table

Molecule The smallest particle of a compound that can exist independently & still have the properties of that substance.

Molecule

Compounds – A substance that contains 2 or more elements that are chemically combined in definite proportions.

Mixtures – made up of 2 or more elements or compounds that do not lose their own physical or chemical properties.

Solutions – mixtures of 2 or more substances where the molecules of one substance are spread out evenly between the molecules of the other substances.

N 2818 Number of Electrons Per Energy Level

Helium Atom Helium 2 He

Some of the electrons in the outermost shell are called valence electrons. These are the electrons that can be gained or lost in a chemical reaction. Valence

Atoms can attain a more stable arrangement of electrons in their outermost shell by interacting with one another. An ionic bond is formed when electrons are transferred from one atom to the other.

A covalent, or molecular, bond is formed when electrons are shared between atoms.

Covalent (Molecular) Bond Sharing Electrons

Metallic Bond In a metallic bond, the outer electrons of the atoms form a common electron cloud. In a sense, the electrons become the property of ALL the atoms. These electrons are described as a "sea of electrons."

Solids Many solids are crystalline. Crystals are bounded by plane surfaces called ‘faces’. Crystals maintain their characteristic faces & angles.

Metals Metals: –Solid at room temperature –Opaque –Conductor of heat –Conductor of electricity –Reflects light like a mirror –Made of microscopic crystals –Expands when heated –Contracts when cooled

Metals Examples of pure metals: –Iron –Copper –Zinc –Tin –Aluminum –Magnesium –Manganese –Vanadium –Molybdenum –Cobalt –Tungsten –Beryllium –Lithium –Zirconium –Titanium

Alloys Pure metals may not have the necessary physical properties Pure metals can be mixed with other metals and non-metals to form ALLOYS ALLOYS may have superior properties to pure metals What types of properties?

Alloys ALLOYS –Made of two or more metals, or –Made of one or more metals mixed with one or more non-metals. –STEEL is an ALLOY of IRON and CARBON –CARBON improves the properties of IRON –Other elements make the properties of iron worse.

Ferrous Alloys Ferrous metals: –Large percentage of IRON –IRON = Fe –Easily weldable –Carbon steel, tool steel, stainless steel, cast iron, etc.

Ferrous Materials Iron Cast Iron Wrought Iron Steel –Carbon Steels Low Carbon Steels Medium Carbon Steels High and Very High Carbon Steels –Alloy Steels

Non-Ferrous Alloys Non-Ferrous metals: –DO NOT contain IRON (Fe) –May contain small amounts of iron as an ALLOYING agent –Aluminum, copper, tin, bronze, brass, zinc, lead, nickel, etc.

Alloys Ionic and covalent bonding result in compounds. Metallic bonding between two (or more) different metals always results in alloys, or mixtures, without fixed compositions. There is not yet a systematic way of naming alloys like those for naming covalent and ionic compounds. In part, this is because alloys are not compounds, their composition is variable and their names need to reflect that. Generally, we use common names like brass, bronze, or steel or technical names like chromium steel or high carbon steel.