cos 1.0, 1.1, 1.2, 1.3 recognize periodic trends of elements, inlcuding the number of valence...
TRANSCRIPT
COS 1.0, 1.1, 1.2, 1.3
• RECOGNIZE PERIODIC TRENDS OF ELEMENTS, INLCUDING THE NUMBER OF VALENCE ELECTRONS, ATOMIC SIZE AND REACTIVITY.
• CATEGORIZE ELEMENTS AS METALS, NONMETALS, METALLOIDS AND NOBLE GASES.
• DIFFERENTIATE BETWEEN FAMILIES AND PERIODS.
• USE ATOMIC NUMBER AND MASS NUMBER AND MASS NUMBER TO IDENTIFY ISOTOPES.
WHAT YOU’LL LEARN• State the charge, mass, & location of each part of an atom
according to the modern model of the atom.• Relate the organization of the periodic table to the
arrangement of electrons within an atom.• Identify isotopes of common elements.• Determine how many protons, neutrons, & electrons an
atom has, given its symbol, atomic number, & mass number.
• Locate alkali metals, alkaline earth metals, & transition metals in the periodic table.
• Locate semiconductors, halogens, & noble gases in the periodic table.
ATOMIC STRUCTURE
WHAT ARE ATOMS?
• smallest part of an element that still has element’s properties.
• building blocks of molecules
WHAT’S IN AN ATOM?
NUCLEUS
• center of each atom • small & dense• has positive electric charge
PROTONS
• subatomic particle that has positive charge • found in nucleus
NEUTRONS
• subatomic particle that has no charge• no overall charge because of equal number
of protons and electrons whose charges exactly cancel
ELECTRONS
• subatomic particles with negative charges. • located in a cloud moving around outside
nucleus
QUARKS
• particles of matter that make up protons and neutrons
MODELS OF THE ATOM
DEMOCRITUS
Greek philosopher developed theory around 400 B.C.proposed that atoms make up all substancesAtom — “unable to be divided”
JOHN DALTON
atomic theory developed in 1808first atomic theory with a scientific basismodel was simple spherethought the atom could not be split
NIELS BOHRtheory developed in 1913Bohr suggested that electrons in an atom move in set paths around the nucleus much like planets orbit the sun in our solar system
It is impossible to determine an electrons?exact location of an electron speed direction
Best scientists can do is?calculate chance of finding an electron in a certain place within an atom
ENERGY LEVELS
• path of a given electron's orbit around a nucleus, marked by a constant distance from the nucleus
• Closer to nucleus, lower energy level of electrons
• Further from nucleus, more energy electrons have
• Number of filled energy levels an atom has depends on number of electrons
ORBITAL
• region in an atom where there is a high probability of finding electrons
VALENCE ELECTRONSVALENCE ELECTRONS
• found in outermost shell of an atom • determines atom’s chemical properties• participate in chemical bonding • Every atom has between one and eight
THE PERIODIC TABLE
ORGANIZATION OF THE ORGANIZATION OF THE PERIODIC TABLEPERIODIC TABLE• Groups similar elements togetherGroups similar elements together• organization makes it easier to predict organization makes it easier to predict
properties of an element based on properties of an element based on where it is in periodic tablewhere it is in periodic table
• Elements are listed in order of number Elements are listed in order of number of protonsof protons
PERIODIC LAW
• states that when elements are arranged this way, similarities in their properties will occur in a regular pattern
• helps determine electron arrangement
PERIODS
• Horizontal rows
• number of protons & electrons increases as you move from left to right
FAMILY/GROUP
• vertical column of elements
• Atoms of elements in same group have same number of valence electrons
• elements have similar properties
IONS
• an atom or group of atoms that has lost or gained one electron and has a negative or positive charge
HOW THE STRUCTURES OF ATOMS DIFFER
ATOMIC NUMBER (Z)ATOMIC NUMBER (Z)
number of protons in the nucleusnumber of protons in the nucleus
MASS NUMBER (A)MASS NUMBER (A)
number of protons plus the number of number of protons plus the number of neutrons in nucleusneutrons in nucleus
ATOMIC RADIUSATOMIC RADIUS is size of atom
GROUPS radius increases as one proceeds down any group of periodic
table WHY?
adding layers of electrons
PERIODS radius decreases as one proceeds across any row of periodic
table WHY?
increasing number of protons in nucleus as you go across the period pulls electrons in more tightly.
ISOTOPEISOTOPE
has same number of protons as other has same number of protons as other atoms of same element do but has a atoms of same element do but has a different number of neutrons.different number of neutrons.
Some are more common than others.Some are more common than others. If you know the atomic number and If you know the atomic number and
mass number of an atom, you can mass number of an atom, you can calculate the number of neutrons it has.calculate the number of neutrons it has.
ExampleExample Chlorine 35 has a mass number of 35. Chlorine 35 has a mass number of 35.
Has an atomic number of 17. Has an atomic number of 17. Mass number (Mass number (AA): ): 3535 Atomic number (Atomic number (ZZ):): –17–17 Number of neutrons:Number of neutrons: 1818
AVERAGE ATOMIC MASSAVERAGE ATOMIC MASS
weighted average of masses of all weighted average of masses of all naturally-occurring isotopes of an naturally-occurring isotopes of an element element
FAMILIES OF ELEMENTS
HOW ARE ELEMENTS CLASSIFIED?
By similar physical & chemical properties.
BASIC PROPERTIES
LUSTER
ability to reflect light
CONDUCTIVITY
ability to conduct heat or an electric current
MALLEABILE
Ability to be hammered or rolled into thin sheets
DUCTILE
Ability to be stretched/drawn into a thin wire
METALS
three categories
ALKALI METALS located in group 1 of periodic table shiny malleable ductile React violently w/ water Very reactive b/c it has only one
valence electron Has +1 charge Not found in nature as elements Found only in compounds Ex: salt (NaCl)Lithium used to treat bipolar disorder
ALKALI EARTH METALS
• located in Group 2 of periodic table• Has two valence electrons• Has +2 charge• shiny• malleable• ductile• Form compounds in stone & human bodyCalcium (Ca):• Shells of sea animals, coral reefs (limestone),
skeletal structure humans …Magnesium (Mg)• Air plane construction• Activates enzymes that speed up processes
in humans• brilliant white color in fireworksMedicines• milk of magnesia • Epsom salt
TRANSITION METALS
• located in groups 3-12• most familiar • found in elemental stateIron• most abundant metal• used in steelAluminum• making containers, automotive parts,
cookware…MERCURY• only metal at room temperature• used in thermostats, thermometers,
batteries …
ALLOY
mixture of a metal with one or more elements that retains original properties of metal
NAME COMP. USE
bronze Copper, tin Jewelry marine
hardware
Brass Copper, zinc Hardware musical
instruments
Sterling silver
Silver, copper
Tableware, jewelry
COMMON ALLOYS
NONMETALS Some elements found in groups 13-16 & all elements in
groups 17-18 except hydrogen usually gases or brittle solids at room temperature poor conductor of heat & electricity may be solids, liquids, or gases at room temperature.
HALOGENS
• located in Group 17• very reactive in elemental state•Chlorine• greenish yellow gas• Kills bacteria• Elemental chlorine is very poisonous• obtained from seawaterFluorine • Poisonous yellow gas• used in toothpasteBromine• Dark red liquid• only nonmetal liquid at room
temperature• obtained from seawaterIodine• shiny, purple-gray solid• Used as disinfectant• obtained from seawater
NOBLE GASES
• located in group 18• Exist only as single atoms
instead of molecules• Unreactive b/c orbitals are full
of electrons• Neon• Signs• Helium• Less dense than air• Gives lift to blimps & balloons• Argon/Krypton• Used in light bulbs
SEMICONDUCTORS
• elements that can conduct electricity under certain conditions
• Aka metalloids:• Composed of only six elements• Boron, silicon, germanium, arsenic,
antimony & tellurium• Boron • Extremely hard• Added to steel to increase
hardness & strength at high temperatures.
• Antimony • Used as fire retardants• Silicon• Makes up 28% of earths crust• Sand most common compound• Used in electronics