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Elements and their properties . Section 1: Metals. Properties of Metals . Discovered gold 6,000 years ago Metals found left of the stair- step line
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Properties of Metals • Discovered gold 6,000 years ago • Metals found left of the stair- step line • Common properties- good conductors of heat and electricity, all but Mercury (Hg) are solid at room temperature. Reflect light (called luster), are malleable, and ductile.
Bonding in metals • Ionic bonding- have 1- 3 electrons in their outer energy levels (remember all atoms are trying to achieve 8 electrons). When metals combine with nonmetals, metals lose electrons • Easier to lose 1- 3 electrons than to gain 5-7. • Take on the electron structure of the nearest noble gas.
Bonding in Metals • Metallic Bonding- positively charged metallic ions are surrounded by a cloud of electrons. • Outer level electrons not held tightly by nucleus but rather move freely through the metal ions. • Responsible for the properties of metals- metal does not break because the ions slide past each other within their electron clouds. Metals conduct electricity because outer- level electrons are weakly held.
The alkali metals • Group 1 • Shiny, malleable and ductile • React rapidly and violently with oxygen and water • One electron in outer energy level • Becomes positively charged in ionic bonds • Francium is radioactive, meaning that the nucleus breaks down and gives off particles and energy. http://www.youtube.com/watch?v=m55kgyApYrY
The alkaline earth metals • Group 2 • Shiny, malleable, and ductile • Combine readily with other elements- not found alone in nature • Two electrons in outer energy level • Has a +2 charge in ionic bonds
Transition Elements • Elements in groups 3- 12 • Occur in nature as uncombined elements • Iron, cobalt, and nickel known as the “iron triad” • Group 11- copper, silver, and gold. Stable, malleable, found as free elements in nature. Known as “coinage metals” • Group 12- zinc, cadmium, and mercury. Used in protective coatings. Mercury accumulates in the body and is dangerous and can be fatal.
Inner transition metals • Two rows disconnected from the rest of the periodic table. • Only done to save room • Lanthanides- first row, elements 58- 71 • Actinides- second row, elements 90- 103 • All are radioactive and unstable. • Uranium- used in nuclear reactors and weapons
Properties of nonmetals • Typically gases or brittle solids are room temperature. Not malleable or ductile. Most do not conduct heat or electricity, are not shiny. • All found to the right of the stair step line except for hydrogen. • Only group 18 is made of all nonmetals.
Bonding in nonmetals • Form ionic and covalent compounds • In ionic bonds, gain electrons from metals, become negative. • When bonding with other nonmetals, form covalent bonds.
Hydrogen • 90% of all atoms in the universe are hydrogen • Hydrogen on its own forms a diatomic molecule • A molecule consisting of two atoms of the same element in a covalent bond • Highly reactive, has a single electron which it shares in covalent bonds. • Also forms ionic bonds in which it receives an electron from metals.
Halogens • Group 17 • Seven electrons in their outer energy level. • Needs to gain one electron from a metal • Forms salts, ionic compounds between halogens and metals. • NaCl • Fluorine most chemically active of all the elements. • Can be dangerous to work with
The Noble Gases • Group 18 on the periodic table • Exist as isolated atoms • Stable because they have 8 electrons in their outermost energy level • No known natural compounds • Used in neon lights
Properties of Metalloids • Form ionic and covalent bonds with other elements and have metallic and nonmetallic properties. • Are “semiconductors”- conduct electricity better than nonmetals but not as well as metals.
The Boron Group • Group 13 • Aluminum is the most abundant metal in the Earth’s crust • Have 3 electrons in outermost energy level • Lose 3 electrons in ionic bonding • Become +3
The Carbon Group • Group 14 • Have 4 electrons in their outermost energy level • Typically only form covalent bonds (too hard to lose or gain 4 electrons) • Carbon compounds are essential to life • Silicon has two allotropes, or different forms of the same element. • Used in semiconductors in electronics
Allotropes of Carbon • Graphite in pencil and diamonds both pure carbon • New allotrope discovered in 1980s called buckminsterfullerene (or “Bucky Balls”) • Used to make carbon nanotubes Graphite Diamond buckminsterfullerene
The Nitrogen Group • Group 15 • 5 electrons in outer energy level • Tend to share electrons and form covalent bonds
The oxygen group (chalcogens) • Group 16 • 6 electrons in outer energy level • Gain 2 electrons in ionic bonds • Become -2 • Oxygen forms diatomic molecules (O2) • Name chalcogen means “chalk former”
Synthetic Elements • Have over 92 protons • Except for technetium 43 and promethium 61 • Formed from smashing elements with particles on a heavy ion accelerator • Elements with over 92 protons are called transuranium elements. • All are synthetic and unstable • Make synthetic elements to understand the forces that hold nuclei together • Most do not last long- many last only fractions of a second.