Transcript Chapter 20 Lecture

Physical Science
Ch. 20
Section 1
Metals
Properties of metals
• Conduct heat and electricity
• Luster
– reflect light well
• Malleable
– can be hammered or rolled into sheets
• Ductile
– can be drawn into wires
• Electron Donors
– combine with nonmetals by losing
electrons
Metallic Bonding
•Positively charged metallic
ions are surrounded by a
cloud of electrons
•Ions are in sliding layers and
electrons are weakly held
•Readily form ionic bonds with
nonmetals
• The Alkali Metals
–softer and more reactive than
other metals
–Highly reactive w/ oxygen & water
–don’t occur naturally as elemental
forms
–Combine readily with other
elements due to single electron in
outer energy level
–Located in 1st column of periodic
table
Uses of Alkali Metals
• Human health
–sodium, potassium, and lithium
compounds
• Photocells
–some depend on rubidium or cesium
• Francium
–a radioactive element which breaks
down giving off particles and energy
• The Alkaline Earth Metals
–not found naturally in
elemental form
–two electrons in outer
energy level
nd
–Located in the 2 column
of the periodic table
Alkaline Earth Metals
• The Applications
–strontium and magnesium found in
fireworks
–magnesium in vehicles, ladders, and
bats
–calcium in statues and countertops
• Uses with the Human body
–calcium in bones
–barium in disease diagnoses
–radium formerly used in cancer
treatments
Transition Elements
• They often occur in nature
as uncombined elements
• Located in the sunken in
area of the periodic table
• The number of valence
electrons have a tendency to
vary (transition) at times
Transition Elements
• Typically form colored compounds
–chromium is in rubies & emeralds
• Iron triad (iron, cobalt, and nickel)
–Iron
• most widely used of all metals
• main ingredient in steel
• abundant in Earth’s crust
–Cobalt and nickel
• used in some steels
–Nickel
• used to coat other metals
• Copper, silver, gold
– coinage metals since once were commonly
used in coins
• Copper
– used in electric wiring because it is a superior
electricity conductor
• Silver
– used in photographic film and paper; jewelry
• Gold
– used in jewelry
• Zinc and cadmium
– often used to coat or plate other metals
• Mercury
– only room temperature liquid metal
– used in thermometers and batteries
Inner Transition Metals
• Rare earth elements
–seem disconnected from the rest
of periodic table
• The Lanthanides Series (1st row)
nd
• The Actinides (2 row)
–All are radioactive and unstable
–Uranium is the best known
Section 2
Nonmetals
Nonmetals
• Properties of nonmetals
–Gases or brittle solids at room
temperature
–Not malleable
–Not ductile
–Poor conductors of heat and
electricity
–Lustrous
–Electron acceptos
Compounds formed by Nonmetals
• Ionic compounds
–form when nonmetals gain
electrons from metals and
become negative ions
• Covalent compounds
–form when nonmetals share
electrons with other
nonmetals
• Sublimation
–a solid changes directly into a
gas without first becoming a
liquid
• Diatomic molecule
–two atoms of the same
element in covalent bond
Magnificent Seven
• 7 diatomic elements
–Always occur with 2 atoms
•
•
•
•
•
•
•
Bromine
Oxygen
Fluoride
Iodine
Nitrogen
Chlorine
Hydrogen
More about nonmetals
• Hydrogen
–most common element in
universe
–diatomic molecule
–Highly reactive element found
mostly on Earth as part of
water compound
More about nonmetals
• The Halogens (7th column)
–A salt forms when a halogen
gains one electron from a metal
• Use of halogens
–Chlorine
• disinfectant and bleach
–Bromine
• dyes in cosmetics
–Iodine
• hormone regulation
Noble Gases
• Exist as isolated, stable atoms
• Located in 8th column
–Have complete outer energy level
filled
• Helium
–used in blimps and balloons
• Neon, argon, and krypton
–used in lights
Section 3
Mixed Groups
• Properties of metalloids
–Located around the stair steps
–Form ionic & covalent bonds
–Have some metallic & some
non-metallic properties
–Partial conduction gives them
semiconductor characteristics
Boron Group
• Named for the first element in 3rd
column
• Has 3 valence electrons
• Boron
– used in water softening products,
antiseptics, and fuels
• Aluminum
– abundant in Earth’s crust
– used in cans, foil wrap, pans,
building materials, and aircraft
Carbon Group
• Named for first element in 4th column
• Four valence electrons
• Carbon
– found in coal, oil, natural gas, and foods
• Silicon
– Occurs as an allotrope
• same element with different molecular
structures
– Found in sand, rocks, and soil
– The main component in semiconductors
• conduct electricity under certain conditions
Carbon Group con’t
• Germanium
–also used in semiconductors
• Tin
–used to coat other metals
• Lead
–toxic, so no longer used in paint
• Allotropes of carbon
–Diamonds
–Graphite
–Buckminsterfullerene
•
•
•
•
Nitrogen Group
th
Named for first element in 5 column
Has five valence electrons
tends to form covalent bonds
Nitrogen
– used to make nitrates and ammonia
• Phosphorus
– used in water softeners, fertilizers, match
heads, fine china
• Antimony and bismuth
– used with other metals to lower their
melting points
Oxygen Group
• Named for first element in 6th column
• Has six valence electrons
• Oxygen
– makes up 20% of air
– is used by living things in respiration
– provides protection from Sun’s radiation
• Sulfur
– used to form sulfides for pigment in paint
• Selenium
– used in photocopiers and multivitamins
• Synthetic Elements (man made)
– Created elements not usually found on
Earth
– synthetic elements usually disintegrate
quickly.
• Uranium
– can be made into neptunium which forms
plutonium when it disintegrates.
• Plutonium
– can be changed into americiun
• used in smoke detectors.
• Transuranium elements
– have more than 92 protons
– are synthetic and unstable
• The study of synthesized
elements helps scientists to
understand the forces holding
the nucleus together.
–Element 114 lasted for 30
seconds.
–It combined 114 protons with 175
neutrons.
–It broke apart due to enormous
repulsion between the protons.