Chapter 5: The Periodic Law General Chemistry

Review/Link to Previous Learning In Chapter 4, we learned about electrons configurations of elements. Discovered there is a pattern of electron configurations on the Periodic Table. Are there other patterns on the Periodic Table? _____________ In Chapter 5 we will learn how the Periodic Table is organized.

Collections Do you like to play cards? Do you have a stamp, baseball card, or comic book collection? How do you organize your collection?

Attempts at Organizing Elements Early scientists knew about some properties of elements. Is there a characteristic of elements that can organize them?

Dobereiner’s Triads THE LAW OF TRIADS: _________________________________________ EXAMPLE: Lithium Atomic Mass of 7 Sodium Atomic Mass of 23 Potassium Atomic Mass of 39 According to Dobereiner’s Law, the atomic mass of sodium Should equal the arithmetic mean of lithium and potassium. (7+39)/2 = 23, which is the mass of sodium.

Problems with Dobereiner’s Law of Triads. 1) ______________________________________ ________________________________________ 2) The law did not work for very low or very high massed elements such as F, Cl, and Br. 3) As techniques improved for measuring atomic masses accurately, the law became obsolete. Dobereiner’s research made chemists look at groups of elements with similar chemical and physical properties.

Newland’s Law of Octaves When placed in increasing order of their atomic masses, __________________________________ ________________________________________. LiBeBCNOF NaMgAlSiPSCl K Ca

Problems with Newland’s Law of Octaves 1) _____________________________________ ________________________________________. 2) When more elements were discovered (Noble gases) they could not be accommodated in his table. However, the modern periodic table does draw from the concept of periods of eight.

Mendeleev and Meyer Published nearly identical schemes for classifying elements Arranged elements by ______________________ Mendeleev generally given more credit –Published first –More successful at demonstrating value of table –______________________________________ ______________________________________

Mendeleev’s Table: ______________________________. He arranged the table so that elements in the same column have similar properties.

Problems with Mendeleev’s Table: 1) The positions of ________________ could not be accommodated within the table. 2) In order to make the elements fit the requirements, Mendeleev was forced to put an element of slightly higher atomic weight ahead of one of slightly lower atomic weight.

Henry Moseley ( ) Developed concept of _________________ –amount of positive charge in the nucleus Later determined that arranging periodic table according to ___________________ eliminated problems seen in Mendeleev’s table

Why is it the “periodic” table? Periodic Law: when elements are arranged in order of increasing atomic number, ____________________________ ____________________________

Study Buddy Review Describe the contribution each person below made to the development of the periodic table: –Johan Dobereiner –John Newland –Dmitri Mendeleev –Julius Meyer –Henry Moseley

Parts of the Periodic Table

Parts of Periodic Table Groups/families: vertical columns –__________________1A –__________________2A –Boron, carbon families –__________________ (oxygen family). –pnictogens (nitrogen family) –__________________ (fluorine family): 7A –___________________8A/0

Horizontal rows are called periods There are 7 periods

1A 2A3A4A5A6A 7A 8A 0 The elements in the A groups are called the representative elements outer s or p filling

Parts of Periodic Table Metals: _____________ of staircase Nonmetals: __________of staircase Metalloids: elements adjacent to staircase (except Al, Po)

The group B are called the transition metals u These are called the inner transition metals and they belong here

Study Buddy Review Identify the follow parts of the periodic table: –Halogens –family –Alkali metals –Metals –Inner transition metals –Noble gases –Metalloids –Period

Periodic Properties of Elements

Periodic Trends Atomic Radius Ionic Radius Ionization Energy Electron Affinity Electronegativity

Atomic Radius Atomic Radius = ____________________________ ___________________________________________ } Radius

Trends in Atomic Radius Influenced by three factors: 1. ________________ –More charge pulls electrons in closer. 2. Energy Level –Higher E level _________________________ 3. Shielding effect –The number of electrons between electrons and nucleus affects the pull felt by the outer electrons

Atomic Radius Group trends As we go down a group... ______________ ______________ ______________ so the atoms get bigger. H Li Na K Rb

Atomic Radius Periodic Trends As you go across a period, the radius gets smaller. ___________________________________ NaMgAlSiPSClAr

Atomic Radius

Ionic Size Ion: electrically charged atom Cation: __________ charged ion Anion: ___________ charged ion Ions aren't the same size as the neutral atoms they come from. –Compare the sizes of sodium and chloride ions with the sizes of sodium and chlorine atoms.

Positive ions are smaller than the atoms they come from. _________________ _________________ _________________ _________________ _________________. Negative ions are bigger than the atoms they come from. Although the electrons are still all in the 3-level, the extra repulsion produced by the incoming electron causes the atom to expand. There are still only 17 protons, but they are now having to hold 18 electrons.

Study Buddy Review-A.R., I.R. Describe the pattern for atomic radius –As you move across a period –As you move down a column What charge does a cation have? What charge does an anion have? Which is larger than its parent atom, a cation or an anion?

First Ionization Energy Ionization energy __________________________ __________________________________________ Elements want to have the e- configuration like that of a noble gas (filled) –Column 1A elements have need to _____ one electron to have noble gas configuration so it is ________ to remove electron –Column 7A element need to GAIN one electron to have noble gas configuration, so it is HARD to remove electron

First Ionization Energy vs. Atomic Number

Ionization Energy

As you move down a group ionization energy decreases… ________________ ________________ ________________  As you move across a period ionization energy increases… Elements on left of table want to lose electrons to have full energy level (requires low energy to remove electron)

Successive Ionization Energies more than one electron can be removed from atoms Second Ionization energy: ______________ _____________________________________ Third Ionization energy: when a third electron is removed from an atom that has already lost two electrons

SymbolFirstSecond Third H He Li Be B C N O F Ne Sucessive Ionization Energies

Relationship Between Common Charge and I.E. Consider Beryllium: –Electron config: [He] 2s 2 Low energy to remove 1 st and 2 nd electrons MUCH higher energy to remove 3 rd electron because ___________________________________ ___________________________________

Study Buddy Review-I.E. What is ionization energy? Describe the pattern for ionization energy as you –Move down a family –Move across a row What does “first” ionization energy mean?

Electron Affinity Electron affinity is: ___________________________________ the more attraction for an electron the energy is released when the atom gains the electron –Released energy is ______________ (-350 kJ)

Electron Affinity

General Trend: ________________ (s 2 p 5 configurations) are most negative electron affinities. They are most likely to want to gain electrons to obtain noble gas configuration As you go down a family, electron affinity is ______________(harder to gain electrons with increasing atomic size)

Study Buddy Review-E.A. What does it mean when an energy is negative? Which elements generally have a very negative electron affinity?

Electronegativity As you move down a group, electronegativity ___________ As you move across a period, electronegativity _____________ u Electronegativity: ___________________ ______________________to itself when it is chemically combined with another element. Which element is the MOST electronegative?

Electronegativity

Study Buddy Review-Electroneg Define electronegativity. Describe the pattern for electronegativity as you –Move down a group –Move across a period Which element is the most electronegative?

Resources dius.htmlhttp:// dius.html ffinity/Period05.htmhttp://wine1.sb.fsu.edu/chm1045/notes/Periodic/A ffinity/Period05.htm _BLB/Chpt07/sld017.htmhttp:// 113_BLB/Chpt07/sld017.htm Jeanette Boles Tina Lula Dr. Stephen L. Cotton, Charles Page High School