# Periodic Trends

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. Mendeleevs 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 _____

Monatomic Ions ions of 1 type of atom Use the periodic table to determine charge of monatomic ions Groups 1-3A: Charge = Group # Groups 5-8A: Charge= Group # - 8

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

Coulombs 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 (from nucleus to bonding electrons) 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 the distance between protons in nucleus and outermost electrons is greater which causes the force of attraction to decrease so the radius

increases. Trend #1: Atomic Size Atomic size decreases across a period because there are more protons in the nucleus and the force of attraction is

greater causing the radius to decrease. Ion Atoms with a charge Cations positive ions that lost electrons

Anions negative ions that gained electrons Monatomic Ions ions of 1 type of atom Use the periodic table to determine

charge of monatomic ions Groups 1-3: Charge = Group # Groups 5-8: Charge= Group # - 8 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 distance between protons in nucleus and outermost electrons is greater

which causes the force of attraction to decrease so the electron is easier to remove. Trend #2: Ionization Energy IE increases as you move left to right across a period because there are more protons in

the nucleus and the force of attraction is greater making it easier to remove the electron. Trend #3: Ionic Size Cations < Neutral < Anions

Consider Na+ < Na < Na- Trend #3: Ionic Size - table of ionic size and atomic size

Trend #3: Ionic Size Ionic size increases down a group because the distance between protons in nucleus and outermost electrons is greater

which causes the force of attraction to decrease so the radius increases. Trend #3: Ionic Size Across a period ionic size of positive ions

and negative ions decreases because there are more protons in the nucleus and the force of attraction is greater causing the radius to decrease. But keep in mind that anions have bigger radii than cations.

Summary of Trends 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 FI Ionic Size F I

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

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