Presentation on theme: "Elemental Properties and Patterns"— Presentation transcript:
1 Elemental Properties and Patterns Periodic TrendsElemental Properties and Patterns
2 Periodic TablePeriodicity: regular variations (or patterns) of properties with increasing atomic number. Both chemical and physical properties vary in a periodic (repeating) pattern.Group: vertical column of elements (“family”)Period: horizontal row of elements
3 Periodic Table and Periodicity Chemistry: The Periodic Table and Periodicity1. Who first published the classification of the elements that is the basis of our periodic table today?2. By what property did Mendeleev arrange the elements?3. By what property did Moseley suggest that the periodic table be arranged?4. What is the periodic law?5. What is a period? How many are there in the periodic table?6. What is a group (also called a family)? How many are there in the periodic table?DMITRI MENDELEEVATOMIC MASSATOMIC NUMBERTHE PROPERTIES OF THE ELEMENTS REPEAT PERIODICALLYA HORIZONTAL ROW IN THE PERIODIC TABLE; 7A VERTICAL COLUMN IN THE PERIODIC TABLE; 18
4 The Periodic Law Mendeleev understood the ‘Periodic Law’ which states: When arranged by increasing atomic number, the chemical elements display a regular and repeating pattern of chemical and physical properties.
5 Metals, Nonmetals, & Metalloids 12Nonmetals345Metals67MetalloidsZumdahl, Zumdahl, DeCoste, World of Chemistry 2002, page 349
6 Groups of Elements Transition metals noble gases alkaline earth metals Elements with similar chemical behavior are in the same group.noble gasesTransition metalsalkali metalshalogensalkaline earth metalslanthanidesactinides
7 MetalsMetals are lustrous (shiny), malleable, ductile, and are good conductors of heat and electricity.They are mostly solids at room temp.What is one exception?Mercury(Hg)
8 Nonmetals Nonmetals are the opposite. They are dull, brittle, nonconductors (insulators).Some are solid, but many are gases, and Bromine is a liquid.
9 Metalloids Metalloids, aka semi-metals are just that. They have characteristics of both metals and nonmetals.They are shiny but brittle.And they are semiconductors.What is our most important semiconductor?
10 Identifying the patterns Periodic trendsIdentifying the patterns
11 Metallic Characteristics metallic character increasesmetallic character increasesmetallic character increases• Elements with the highest ionization energies are those with the most negative electron affinities, which are located in the upper-right corner of the periodic table.• Elements with the lowest ionization energies are those with the least negative electron affinities and are located in the lower-left corner of the periodic table.• The tendency of an element to gain or lose electrons is important in determining its chemistry.• Various methods have been developed to describe this tendency quantitatively.• The most important method is called electronegativity (), defined as the relative ability of an atom to attract electrons to itself in a chemical compound.
12 Periodic Table and Periodicity Chemistry: The Periodic Table and Periodicity1. Who first published the classification of the elements that is the basis of our periodic table today?2. By what property did Mendeleev arrange the elements?3. By what property did Moseley suggest that the periodic table be arranged?4. What is the periodic law?5. What is a period? How many are there in the periodic table?6. What is a group (also called a family)? How many are there in the periodic table?DMITRI MENDELEEVATOMIC MASSATOMIC NUMBERTHE PROPERTIES OF THE ELEMENTS REPEAT PERIODICALLYA HORIZONTAL ROW IN THE PERIODIC TABLE; 7A VERTICAL COLUMN IN THE PERIODIC TABLE; 18
14 Variable – factor in the experiment that is being tested
15 The factor that is changed is known as the independent variable (IV). Also referred as “The Cause”The factor that is measured or observed is called the dependent variable (DV).Also referred as “The Effect”
16 Rule for Addition and Subtraction Calculating with Numbers Written in Scientific Notation In order to add or subtract numbers written in scientificnotation, you must express them with the same power of 10.Sample Problem: Add 5.8 x 103 and x 104(5.8 x 103) + (21.6 x 103) =27.4 x 1032.74 x 104Exercise: Add 8.32 x and 1.2 x 10-51.28 x 10-5
23 Atomic Radii Trend: decreases across a period WHY??? As the # of protons in the nucleus increases, the positive charge increases and as a result, the “pull” on the electrons increases.Trend: increases down a groupWHY???The atomic radius gets bigger because electrons are added to energy levels farther away from the nucleus decreasing the “pull” or force of attraction.
25 Ionization EnergyDefinition: energy required to remove outer electrons from an atom
26 Hungry for Tater Tots?Mr. C at 7 years old.Photograph is of me (Mr. Christopherson in 1973, age 7)Story that goes along with this slide is told in class.
27 OUCH!!Atoms tend to lose, gain or share electrons to reach a total of eight valence electrons, called an octet.The octet rule explains the stoichiometry of most compounds in the s and p blocks of the periodic table.Number eight corresponds to one ns and three np valence orbitals, which together can accommodate a total of eight electrons.
28 Ionization Energy Trend: decreases down a group WHY??? Trend: increases across a periodWHY???All the atoms in the same periodIncreasing the number of protons increase the “pull” or force of attraction.Trend: decreases down a groupWHY???Electrons are further away from the positive “pull” of the nucleus and therefore easier to remove.
29 First Ionization energy HeNeArKrHLiNaKRbFirst Ionization energyAtomic number
30 ElectronegativityDefinition: the tendency of an atom to attract electrons to itself when chemically combined with another element
31 Electronegativity Trend: increases across a period (noble gases excluded!)WHY???Nuclear charge is increasing, atomic radius is decreasing; attractive force that the nucleus can exert on another electron increases.Trend: decreases down a groupWHY???The electrons are farther away from the nucleus; decreased attraction, so decreased electronegativity