Periodic Trends Elemental Properties and Patterns Periodic Table

Periodic Trends Elemental Properties and Patterns

Periodic Table • Periodicity: 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

Periodic Table and Periodicity Chemistry: The Periodic Table and Periodicity 1. Who first published the classification of the elements that is the basis of our periodic table today? DMITRI MENDELEEV 2. By what property did Mendeleev arrange the elements? ATOMIC MASS 3. By what property did Moseley suggest that the periodic table be arranged? ATOMIC NUMBER 4. What is the periodic law? THE PROPERTIES OF THE ELEMENTS REPEAT PERIODICALLY 5. What is a period? How many are there in the periodic table? A HORIZONTAL ROW IN THE PERIODIC TABLE; 7 6. What is a group (also called a family)? How many are there in the periodic table? A VERTICAL COLUMN IN THE PERIODIC TABLE; 18

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.

Metals, Nonmetals, & Metalloids 1 Nonmetals 2 3 4 5 Metals 6 7 Metalloids Zumdahl, De. Coste, World of Chemistry 2002, page 349

Groups of Elements Transition metals lanthanides actinides halogens noble gases alkali metals alkaline earth metals Elements with similar chemical behavior are in the same group.

Metals • Metals 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)

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

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?

Periodic trends Identifying the patterns

Metallic Characteristics metallic character increases llic ta me acte r a ch r ses a e r inc

Periodic Table and Periodicity Chemistry: The Periodic Table and Periodicity 1. Who first published the classification of the elements that is the basis of our periodic table today? DMITRI MENDELEEV 2. By what property did Mendeleev arrange the elements? ATOMIC MASS 3. By what property did Moseley suggest that the periodic table be arranged? ATOMIC NUMBER 4. What is the periodic law? THE PROPERTIES OF THE ELEMENTS REPEAT PERIODICALLY 5. What is a period? How many are there in the periodic table? A HORIZONTAL ROW IN THE PERIODIC TABLE; 7 6. What is a group (also called a family)? How many are there in the periodic table? A VERTICAL COLUMN IN THE PERIODIC TABLE; 18

Experiment Variable – factor in the experiment that is being tested

• 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”

Rule for Addition and Subtraction Calculating with Numbers Written in Scientific Notation In 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 103 Exercise: Add 8. 32 x 10 -7 and 1. 2 x 10 -5 2. 74 x 104 1. 28 x 10 -5

http: //phet. colorado. edu/en/simulation/balloons

Attraction and Repulsion of Electrical Charges + - Particles with opposite charges attract one another. + + Particles with like charges repel one another. -

Coulombic Attraction Depends on: 2+ 1+ 2 - 1 - • 1. Amount of charge 2+ 2+ 2 - 2 - • 2. Distance between charges

Periodic Trends • atomic radius. • Radius is the distance from the center of the nucleus to the “edge” of the electron cloud.

Atomic Radii

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 group WHY? ? ? – 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 Energy • Definition: energy required to remove outer electrons from an atom

Hungry for Tater Tots? Mr. C at 7 years old.

OUCH!!

Ionization Energy • Trend: increases across a period • WHY? ? ? • All the atoms in the same period – Increasing the number of protons increase the “pull” or force of attraction. • Trend: decreases down a group • WHY? ? ? – Electrons are further away from the positive “pull” of the nucleus and therefore easier to remove.

He Ne Ar First Ionization energy Kr H Li Na K Rb Atomic number

Electronegativity • Definition: the tendency of an atom to attract electrons to itself when chemically combined with another element

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 group • WHY? ? ? – The electrons are farther away from the nucleus; decreased attraction, so decreased electronegativity

Electronegativity. Trends

Summing Up Periodic Trends

Summing Up Periodic Trends In as e r c in tio a z i n g io n gy r e en us i d n ra o I ing s a re Inc

Which has the largest atomic radius? 7. Br- Br 8. Al+ Al As an atom gains electrons, the atom gets bigger As an atom loses electrons, the atom gets smaller