Classification of Elements 1829 German Chemist JW Dobereiner published a classification system to sort elements Noted trends and patterns related to chemical properties Classified the elements into TRIADSsets of three elements of similar properties ID: 738235
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Slide1
Periodic Trends ChemistrySlide2
Classification of Elements1829 German Chemist J.W. Dobereiner published a classification system to sort elements
Noted trends and patterns related to chemical properties
Classified the elements into TRIADS(sets of three elements of similar propertiesSlide3
1st Periodic Table
1871
Dmitri Mendeleev- a Russian chemist who arranged elements in order of their increasing atomic massesSlide4
Modern Periodic TableHenry G.J.Moseley
Father of Modern Periodic Table
1913 British Physicists
determined the atomic number for each known element
Arranged the periodic table according to increasing atomic numbersSlide5
ROWS= PERIODS OR SERIESAdjacent elements in each horizontal row(period) differ in both chemical and physical properties but the properties change in a regular way across each periodSlide6
COLUMNS= GROUPS OR FAMILIESProperties of elements in any vertical column do differ. They are similar but not identical in chemical behavior.Why do elements in a group have similar properties?
Similar electron arrangementsSlide7
IUPAC International
U
nion of
P
ure and
A
pplied
C
hemistry –the organization that sets standards for chemistry1985 proposed a new system for labeling periodic table.
Groups 1-18 labeled in black from left to right
Used in U.S. and Europe
Divided into metals, nonmetals and metalloidsSlide8
METALS80% of elements
PROPERTIES OF METALS
DUCTILE-can be drawn into wires
HIGH LUSTER
MALLEABLE- can be hammered or rolled into sheets
GOOD CONDUCTORS of heat & electricity
METALLIC BONDING-electrons are layered and the outer layers are weakly heldSlide9
METALLIC BONDINGA type of bonding that is neither ionic nor covalentThe outermost electrons wander freely through the metalSlide10
NonMetalsMost are gaseous at room temperature
Some are solid and one is liquid(Bromine)
Dull
Brittle and powdery
Poor conductors of heat and electricity
Not malleable or ductile
Generally have low melting points
H, C, N, P, As(Arsenic), O, S, Se(Selenium), & Group 17 & 18.Slide11
METALLOIDSProperties of both metals and nonmetalsDepending on the conditionsMost are semiconductors-a substance that can conduct electricity under given conditions
Used to make computer chipsSlide12
Structure of Periodic TableDisplays symbols and names of the elements and infoElements are sorted based on their electron configuration and location on table
Noble gases
R
epresentative elements
Group B Elements
Transition metals
Inner transition metalsSlide13
While atoms of different elements have different numbers of electrons, they may have the same number of electrons in their outer energy levelsSlide14
Electron Configurations in GroupsNoble gases- inert gases
Group 18 or 8A
s & p
energy levels
filled
Orginally
called noble because they did not “mix” with common “folk” or other elements. However some compound have been made in laboratory settings
.
Inert=rarely take place in chemical reactions
Contain 8 electrons in their outer most energy level and are therefore very stable.
Used in “Neon” signs and laser shows.Slide15
Electron Configurations in GroupsRepresentative ElementsGroups 1A-7A ( 1,2, 13,14,15,16,17)
Wide range of physical and chemical properties
Metals, Nonmetals, & Metalloids
Solids-Bromine only liquid
s & p
of highest energy levels
not filled
Group number equals valence electronsSlide16
HYDROGEN-Group 1A(nonmetal) H
2
= DIATOMIC MOLECULE
90 % of all atoms in the universe are Hydrogen
Found in foods, and water and account for 60% of body mass
Reactive(
ie
. H2 burns in oxygen to form H
2O)Hydrogen will share e’ with NONMETALS or
Hydrogen will gain an e’ from METALSSlide17
Group 1A-Alkali MetalsArabic word
al
aqali
= the ashes
Wood ashes are high in Na and K
Highly reactive and found naturally only in compounds
One valence electronSlide18
Group 2A- Alkaline Earth MetalsLithium Compounds are used to treat bipolar disordersLithium is used in rechargeable batteries
Francium- radioactive and extremely rare( only 25-30 g can be found in the Earths crust at one time)
Sodium-hard as butter and can be cut w/ a knife. Can float in water
NaCl
-table salt-obtained from evaporation of seawater or from
lg
salt deposits on the surface of Earth or underground
Essential dietary salt
Potassium- stored in oil because will react violently with water vapor and oxygen in air
Cesium must be kept in sealed glass tube containing argon gas.Slide19
Group 2A-Alkaline Earth MetalsContain two valence electronsHighly reactive
Found in nature in compounds
Calcium
Body needs for strong bones and teeth
Calcium Carbonate-chalk, limestone, coral, and pearls.
Toothpaste may contain Calcium carbonate to help polish teeth
Plaster cast contains calcium sulfate Slide20
Group 2A-Alkaline Earth MetalsMagnesiumKey role in photosynthesis-found in chlorophyll molecules
Used in alloys-strong as steel yet lighter
Cars, bicycles, and backpacks
Used to produce bright white color in fireworks
Old flash bulbs of cameras
Strontium
Used to produce bright red color
in fireworks
Barium compounds
used to diagnose some digestive disorders
Radium
radioactive and once used to treat cancers
Beryllium
lightweight, strong, hard metal that is easy to shape
used in nuclear weapons and reactors.Slide21
MIXED GROUPS Groups 13-16Vertical groups that contain combinations of METALS, NONMETALS, AND METALLOIDS.Named for the first element of the family/group.Slide22
BORON GROUP Group 3A Boron-(METALLOID) Boric Acid used to kill insects & make polymers like slime, Borax used to whiten clothes.
Aluminum(METAL)-cans, foil, etc
Gallium, Indium, and Thallium(METALS) are used to produce semiconductors(conduct electric current under certain conditions)Slide23
CARBON GROUP Group 4A
Carbon
Contains
four electrons in outer energy level
VERY VERSITILE
2
ND
common element in bodyNonmetal Allotropes-different forms of the same element having different molecular structures.
Graphite(hexagonal) carbon bonded w/3 other carbons
Silicon,
Germainum
(METALLOID) also used to produce semiconductors
Tin
(METAL)-typical properties
Lead-
(typical METAL)-too much in bloodstream can lead to organ damage
especially
in yo
ung children.Slide24
ALLOTROPES OF CARBONDiamond STRUCTURE
GRAPHITE STRUCTURE
(tetrahedron)carbon bonded w/ 4 other carbons
(hexagonal) carbon bonded w/3 other carbonsSlide25
NITROGEN GROUP Group 5AContain 5 valence electrons(covalent)
Nitrogen
-NONMETAL; diatomic molecule N2
80% of every breath
4
th
element in abundance in body
Phosphorus =NONMETAL
Arsenic & Antimony=METALLOIDS
Bismuth
=METALSlide26
OXYGEN GROUP Group 6A Contains 6 valence electrons
Oxygen –NONMETAL, diatomic molecule O2
20% of air
O3-ozone molecule; an allotrope of O2
What is the benefit of ozone?
Sulfur & Selenium-NONMETALS
Selenium is used in dandruff shampoos
Tellurium & Polonium-METALLOIDS
Polonium is most toxic element knownSlide27
HALOGENS Group 7A Salt Formers-produce “salts”
Halogens have seven(7) electrons in their outer energy level
If an halogen gains and electron from a metal(ionic) a salt is formed
When in gaseous state they form diatomic(covalent)molecules and give distinctive colors.
Fluorine
is the most chemically reactive
Iodine
is a grey solid at room temperature that is obtained from brine. When heated it changes directly into a purple vapor without forming a liquid(sublimation). What role does iodine play in the body?
Bromine
-used in some cosmetic dyes.Slide28
Electron Configurations in GroupsGroup B Elements
Classified according to electron configurations
Transition Metals
Inner Transition Metals
Transition Metals
Highest
s
sublevel and nearest
d sublevel contain electrons
Inner Transition Metals
f
orbitals
contain
electrons, contain 1 or 2 valence electrons
Once thought to be rare earth metals now known to be most abundant
Lanthanoid
Series(Elements #57-71)
Actinoid
Series( Elements # 89-103)
Transuranium
Elements(#93-118) are all synthetic. Slide29
Transition Elements
IRON TRIAD
Iron, Cobalt, & Nickel
First elements of groups 8,9, &10
They have magnetic properties
All three are used to create steel and other metal mixtures
Nickel is added to steel for strength & shiny protective coating to other metals
Iron is the 2
nd
most abundant in Earth crust
CoINAGE
METALS
Copper, silver, & gold
First three members of Group 11
Stable, very malleable and ductile
Found in elemental form in nature
Used to make coins and jewelry
Copper is used in electrical wiring
Silver Iodide and Silver bromide are used in photography paper Slide30
Zinc, Cadmium, & MercuryFirst three elements of group 12Zinc and Cadmium are used to electroplate other metals
Cadmium
is used in rechargeable batteries (Ni-
Cd
)
Mercury- silvery liquid metal at room temperature.
Used in thermometers, thermostats, switches, and batteries. Poisonous and accumulates in the body.Slide31
SYNTHETIC ELEMENTS Periods 6 & 7Synthetic elements are those created in laboratory settings or “synthesized”
There are
24
synthetic elements-12 of which are in the
Lanthanoid
&
Actinoid SeriesSlide32
Synthetic Elements cont’d
Lanthanoid
Series
(Elements #57-71)
Promethium-used to power pacemakers and artificial hearts
Actinoid
Series
( Elements # 89-103)
Americium-found in smoke detectors
Transuranium
Elements(#93-118) are all synthetic. These are the elements with atomic numbers higher than uranium(#92)
Plutonium-most toxic element known
All synthetic elements are radioactive.
Why? These elements have higher atomic number and are held together less securely than other elements which have fewer p+ and n
0
in their nucleus. Therefore particle or energy can escape from their nuclei,
ie
. Alpha particles, beta particles, and gamma rays.Slide33
SYNTHETIC ELEMENTS cont’dPlutonium-most toxic element knownAll synthetic elements are radioactive.
Why? These elements have higher atomic number and are held together less securely than other elements which have fewer p+ and n
0
in their nucleus. Therefore particle or energy can escape from their nuclei,
ie
. Alpha particles, beta particles, and gamma rays.Slide34
Electron Configurations of GroupsSlide35
Periodic TrendsSlide36
Periodic Law----Periodic TrendsPERIODIC LAW: WHEN ELEMENTS ARE ARRANGED IN ORDER OF INCREASING ATOMIC NUMBER, THERE IS PERIODIC REPETITION OF PHYSICAL AND CHEMICAL PROPERTIES
The properties of the elements within a period change as you move across a period from left to right.
The pattern of properties within a period repeats as you move from one period to the nextSlide37
What are alternative names for these?Slide38
Atomic Radius (Atomic Size)Atomic radius is ½ distance between the nuclei of two atoms of the same element when joined together.
Measured in
picometers
( 1x 10
12
, one trillion)
Atomic size increases from top to bottom in a group
Atomic size decreases from left to right across a periodSlide39
INCREASES from
RIGHT
LEFT
TOP
BOTTOM
HOW DOES ATOMIC RADIUS INCREASE?Slide40
HOW DOES ATOMIC RADIUS INCREASE?Slide41
Cation vs. Ion SizeCations
(lose electrons become smaller)
Anions
(Gain electrons become larger)Slide42
RANK FROM SMALLEST RADIUS TO BIGGESTFluorineHeliumCesium
Francium
Vanadium
Zinc
Silicon
Yttrium
Phosphorus
Jumpstart
4 minutesSlide43
IONIZATION ENERGYSlide44
IONIZATION ENERGYIonization energy is the amount of energy used to remove an electron
Electrons move to higher energy levels when the atom absorbs energy
Electrons need energy to escape the attractive force of the protons Slide45
IONIZATION ENERGYSlide46
IONIZATION ENERGYINCREASES FROM LEFT TO RIGHT ACROSS A PERIOD
Takes more energy to remove e’ from a nonmetal than a metal
DECREASES FROM THE TOP OF A GROUP TO THE BOTTOM
Ex. K has a lower ionization energy than Na.
it is easier to remove an e’ from K than Na.
K is more reactive than NaSlide47
IONIZATION ENERGYSlide48
Element
Atomic #
Ionization Energy
H
1
13.6
Li
3
5.4
K
19
4.3
Na
11
5.1
P
15
11.0
Cl
17
13.0
HOW DOES IONIZATION EN. INCREASE?
L
R, RL, Top Bottom, Bottom Top?Slide49
ELECTRONEGATIVITYSlide50
ElectronegativityWhen atoms bond with each other to form molecules, they share their electrons.
Electronegativity
is the ability an atom has to attract other electrons. Atoms that have high
electronegativities
will attract more electrons and may even steal from other atoms.
Atoms
with low
electronegativities will share the most, sometimes to the point of losing their own electrons. Slide51
Electronegativity Slide52
Elements in the same group have similar behaviors
Because they have the same number of valence electrons!!!
BUT MAGNITUDE CHANGES!Slide53
ReactivitySlide54
REACTIVITYAtoms will undergochemical reactions to Become stable.
Remember: The nature of the universe is that of chaos and all matter is trying to achieve some degree of stability.
Can you think of some examples?Slide55
OCTET RULETHE GOAL OF AN ATOM IS TO HAVE 8 VALENCE ELECTRONS OR A FULL OUTER ENERGY LEVELTHE EXCEPTIONS ARE H AND He
The # of e’ in the outer energy level will determine the chemical properties of the element i.e. different elements with the same # of e’ in the outer energy level will have similar chemical propertiesSlide56
Reactivity
Metals –
more reactive as you go
DOWN a group
Easier to lose electrons
because valence electrons are further away from nucleus
Lower ionization energy
Non-metals –
more reactive as you go
UP
Smaller the atom the more it wants an electron to gain
Higher electronegativity means its easier to take one from another atomSlide57
Reactivity
Most Reactive
Most Reactive
Closest to a
Full
Octet
Full
Valence Shell
Least Reactive
INERTSlide58
ReactivitySlide59
Periodic Trends Summarized