Periodic trends

Periodic TrendsElemental Properties and PatternsThe Periodic LawMendeleev 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.Chemistry: The Periodic Table and Periodicity 1. 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; 7

A VERTICAL COLUMN IN THE PERIODIC TABLE; 18

Periodic Table and Periodicity3NonmetalsNonmetals are the opposite.They are dull, brittle, nonconductors (insulators).Some are solid, but many are gases, and Bromine is a liquid.

Transition metalsalkali metalsalkaline earth metalshalogensnoble gaseslanthanidesactinidesGroups of ElementsElements with similar chemical behavior are in the same group.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)MetalloidsMetalloids, 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?

Periodic trendsIdentifying the patternsMetallic Characteristicsmetallic character increasesmetallic character increasesmetallic character increases11 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.

Chemistry: The Periodic Table and Periodicity 1. 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; 7

A VERTICAL COLUMN IN THE PERIODIC TABLE; 18

Periodic Table and Periodicity12

ExperimentVariable factor in the experiment that is being tested

14The 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 Effect15Rule for Addition and SubtractionCalculating with Numbers Written in Scientific NotationIn order to add or subtract numbers written in scientific notation, you must express them with the same power of 10.Sample Problem: Add 5.8 x 103 and 2.16 x 104(5.8 x 103) + (21.6 x 103) = 27.4 x 103Exercise: Add 8.32 x 10-7 and 1.2 x 10-5 1.28 x 10-5

2.74 x 10416http://phet.colorado.edu/en/simulation/balloons

Attraction and Repulsion of Electrical Charges++Particles with opposite charges attract one another.Particles with like chargesrepel one another.--+-Coulombic AttractionDepends on:1. Amount of charge2. Distance between charges1+1-2-2+2-2+2-2+Periodic Trendsatomic radius.Radius is the distance from the center of the nucleus to the edge of the electron cloud.Atomic Radii

Atomic RadiiTrend: decreases across a periodWHY???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. Atomic Size Trends

Ionization EnergyDefinition: energy required to remove outer electrons from an atom

Hungry for Tater Tots?

Mr. C at 7 years old.26Photograph is of me (Mr. Christopherson in 1973, age 7)Story that goes along with this slide is told in class.

OUCH!!

27Atoms 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.

Ionization EnergyTrend: increases across a periodWHY???All the atoms in the same period Increasing 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.First Ionization energyAtomic numberHeNeArKrHLiNaKRb29ElectronegativityDefinition: the tendency of an atom to attract electrons to itself when chemically combined with another element

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.ElectronegativityTrend: decreases down a groupWHY???The electrons are farther away from the nucleus; decreased attraction, so decreased electronegativityElectronegativityTrends

Summing Up Periodic Trends

Summing Up Periodic Trends

Increasing Ion radius

Increasing ionization energy34Which has the largest atomic radius?7. Br- Br8. Al+ AlAs an atom gains electrons, the atom gets biggerAs an atom loses electrons, the atom gets smaller