Chapter 19 Elements and Their Properties. 19.1 Metals.
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Transcript of Chapter 19 Elements and Their Properties. 19.1 Metals.
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Chapter 19Elements and Their Properties
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19.1Metals
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Properties of Metals
• Metals have common properties• Good conductors of heat and electricity• All but Mercury are solid at room temperature• Reflect light – Luster• Easily hammered/rolled into sheets –
Malleable• Easily drawn into wires - Ductile
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Ionic Bonding
• Metal atoms have usually 1-3 valence electrons
• Tend to give their electrons up easily
• When they combine with nonmetals, they lose electrons to the nonmetals, forming ionic bonds
• This makes them more chemically stable
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Metallic Bonding
• Occurs among metal atoms
• Positive charged metallic ions are surrounded by a cloud of electrons
• The electrons move freely among many different positively charged metal ions
• Explains many properties of metals• Hammered• Good conductors
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Alkali Metals
• Group one
• Properties• Shiny• Malleable• Ductile• Softer• Most reactive of all the metals – react
rapidly/violently w/ oxygen and water• Don’t occur in elemental form in nature –
stored in oil
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Alkali Metals
• One electron in its outer energy level• The atom gives up this electron with it
combines with another atom ex. NaCl
• Living things need alkali metals/their compounds• K, Na, Li
Radioactive Element – one in which the nucleus breaks down and gives off particles and energy
ex. Francium – very rare & radioactive
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Alkaline Earth Metals
• Group 2
• Also not found as free elements in nature – combine so readily with other elements
• 2 electrons in outer energy level• These are given up with they combine with
nonmetals and becomes a positively charged ion in a compound such as CaF2
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Alkaline Earth Metals
• Magnesium & Strontium – used in fireworks
• Chlorophyll – Magnesium compound – enables plants to make food
• Magnesium’s lightness & strength• Cars, planes, spacecraft• Household ladders, baseball/softball bats
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Alkaline Earth Metals
• Calcium compounds needed for life• Calcium phosphate – makes bones strong
• Barium compound – swallowed to take x-rays to diagnose internal abnormalities
• Radium once used to treat cancer• They now use other readily available
radioactive elements
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Transition Elements
• Elements in Groups 3-12
• Often occur in nature as uncombined elements b/c they are more stable
• Often form colored compounds
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Iron, Cobalt, Nickel
• Called the Iron Triad
• Used to create steel/other metal mixtures
• Nickel – added to some metals to make them stronger or give them a shiny protective coating
• Iron – main component of Steel – most widely used of all metals• Second most abundant metallic element in
Earth’s crust (Al is 1st)
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Copper, Silver, Gold
• Very stable and malleable
• Found as free elements in nature
• Copper often used in electrical wiring
• Silver compounds – photographs, film
• Silver & Gold – used in jewelry
• Once used to make coins – termed the coinage metals• Not anymore b/c $$$, most coins now are Ni and
Cu
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Zinc, Cadmium, Mercury
• Zn, Cd often used to coat other metals
• Cd used in rechargeable batteries
• Hg – silvery, liquid metal• Used in thermometers, thermostats, switches,
batteries• Poisonous – can accumulate in body
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Inner Transition Metals
• Lanthanides – follow the element lanthanum
• Used with carbon to make compound used to make movies
• Used to produce color in TV screens
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Inner Transition Metals
• Actinides – second row
• Follow the element actinium
• All radioactive and unstable
• Used to make high quality camera lenses, nuclear reactors, weapons
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Questions
1. How is metallic bonding different from covalent bonding (when two elements share electrons)
2. How would you test something to see if it is a metal?
3. Why is mercury rarely used in thermometers that take body temperature?
4. Explain why copper is a good choice for use in electrical wiring. What type of elements would not work well for this purpose?
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19.2Nonmetals
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Properties of Nonmetals
• Nonmetals – elements that are usually gasses or brittle solids at room temperature
• Not malleable or ductile
• Most don’t conduct well
• Generally not shiny
• All nonmetals except hydrogen are found to the right of the stair step line
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Bonding in Nonmetals
• Electrons in most nonmetals are attracted to the nucleus of the atom, so they are poor conductors
• Can form ionic or covalent bonds
• When nonmetals get electrons from metals, they become the NEGATIVE ions in ionic compounds
• When bonding w/ other nonmetals, usually share electrons to form covalent compounds
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Hydrogen
• 90% of atoms in the universe are hydrogen• Most on earth found in water
When water is broken down, H becomes a gas made up of diatomic molecules
Diatomic molecule – 2 atoms of the same element in a covalent bond
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Hydrogen
• Highly reactive
• Single electron – shared when combined with other nonmetals
• Hydrogen can gain an electron when combining with alkali and alkaline earth metals to form a hydride ex. NaH (sodium hydride)
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Halogens
• Group 17
• Very reactive in elemental form
• Compounds have many uses
• Fluorides – toothpaste, city water, water to disinfect
• 7 electrons in outer energy level, so only need 1 to be HAPPY ☺
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Halogens
• If a halogen gains an electron from a metal, forms an ionic compound called a Salt ex. NaCl
• In gas state, halogens form reactive diatomic covalent molecules – can be identified by colors• Chlorine – greenish
yellow• Bromine – reddish
orange• Iodine - violet
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Halogens
• Fluorine – most chemically active of all elements
• Uses of Halogens• Chlorine compounds – distinct small, most
abundant halogen, used in bleaches to whiten things
• Bromine – only liquid nonmetal at room temp., used in dyes in cosmetics
• Iodine – shiny solid at room temp, when heated changes directly to purple vapor – sublimination• Essential to diet to produce certain hormones
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Noble Gases
• Stable• Outermost energy levels fullNeon and Argon - neon lightsLightweight helium used in balloonsArgon and Krypton used in electric light bulbs to produce light in lasers