Unit 4: The Periodic Table

Periodic Table _______________ was the first person to find a way to list elements in order of increasing atomic mass

Periodic Table He constructed the first periodic table in 1869, an arrangement of the elements according to similarities in their properties.

Mendeleev’s Periodic Table

Periodic Table In 1913, ______ determined the atomic number of atoms and arranged the modern periodic table according to atomic number .

Modern Periodic Table Each element is identified by its symbol placed in a square

Modern Periodic Table The horizontal rows of the periodic table are called _____ There are ___

Modern Periodic Table Each vertical column is called a ____ or ____ There are ____.

Periodic Table A periodic law means that physical and chemical properties of elements are functions of their atomic numbers Elements in the same group on the periodic table have similar properties

Modern Periodic Table Group A elements are called the representative elements because they have a wide range of chemical and physical properties Name the groups in Group A

Modern Periodic Table Group B elements are called the ______________ The inner transition elements are the ______ and _____

Modern Periodic Table The representative elements can be divided into three broad classes; Metals, Nonmetals, and Metalloids What are some characteristics of each?

Classifying Elements by Electron Configuration

Practice: Write in shorthand and noble gas notation for: F, K, Co, Kr, Ce

Classifying Elements by Electron Configuration Blocks on the periodic table - (s,p,d,f) Group number equals the number of electrons in the outermost energy level

Classifying Elements by Electron Configuration Each period number corresponds to the outermost principle energy level

Practice: Identify the block (s,p,d,f) of the periodic table that this element is located. A) Zinc B) Sodium C) Uranium D) Nitrogen

Periodic Trends

Coulomb’s Law Forces of attraction between particles depend on charge of particles and distance between them Higher charge = stronger attraction Shorter distance = stronger attraction

Trend #1: Atomic Size Measured by the radius of an atom via x-ray diffraction

Trend #1: Atomic Size - below is a graph of periodic table showing atomic size trends down a group and across a period

Trends in Atomic Size Atomic size increases down a group because electrons are added to higher energy levels, which are further away from the nucleus. Since there is less of an attraction of the nucleus for the electrons, the atom is larger.

Trend #1: Atomic Size Atomic size decreases across a period because within the same energy level, each element has one more p+ and e- than the preceding element. Therefore, outmost e’s are attracted more closely to the nucleus due to higher charge making it smaller.

Ion Atoms with a charge Cations – positive ions that lost electrons Anions – negative ions that gained electrons

Ion Predict the charge of the ion typically formed by the elements in groups 1-8 on the periodic table

Trend #2: Ionization Energy (IE) IE is the energy required to overcome attraction to the nucleus and remove an electron from an atom.

Trend #2: Ionization Energy -graph of IE versus atomic number

Trend #2: Ionization Energy -graph of IE in groups and periods on the periodic table

Trend #2: Ionization Energy Notice how the IE can be used to see charge of ion

Trend #2: Ionization Energy IE decreases as you move down a group because the outermost electron is not as attracted to the nucleus because it is further away so it is easier to remove.

Trend #2: Ionization Energy IE increases as you move left to right across a period because more p+ in the nucleus lead to greater attraction for the e- in the same energy level.

Trend #3: Ionic Size Cations < Neutral < Anions Consider the attraction of the nucleus for the outermost electrons to see why this is true

Trend #3: Ionic Size - table of ionic size and atomic size

Trend #3: Ionic Size Ionic size increases down a group because the electrons are in energy levels further away from the nucleus and there is less attraction.

Trend #3: Ionic Size Across a period ionic size of positive ions and negative ions decreases But keep in mind that anions have bigger radii than cations.

Summary of Trends

Explain why a Mg atom is smaller than both Ca and Na atoms. Review Explain why a Mg atom is smaller than both Ca and Na atoms.

Review Explain why a K atom has a smaller ionization energy than both Ca and Li atoms.

Review The two ions K+ and Ca2+ each have 18 e-. Which would you expect to have a smaller radius? Justify your answer.

Review Atomic size F I IE F I Ionic Size F I EN F I EA F I

Review Atomic size Cs Ba IE Cs Ba Ionic Size Cs Ba EN Cs Ba EA Cs Ba