Anything in black letters = write it in your notes (‘knowts’) Lesson 6 The Periodic Table Anything in black letters = write it in your notes (‘knowts’)

Objectives for Lesson 6 Section 1 – Organizing the Elements Section 2 – Periodic Trends Describe ways in which the modern periodic table is organized Understand electron configuration patterns in the periodic table Describe and explain trends in the periodic table

Section 1 – Organizing the Elements Dmitri Mendeleev (1869) – created 1st modern periodic table.

Mendeleev arranged elements with similar properties. He also left gaps where proposed elements should be. These gaps were later filled in as more elements were discovered. Ga & Ge Discovered later Similar properties

Mendeleev’s table was an accepted success because it predicted the properties of elements that had not yet been discovered. Woo Hoo!

Today’s periodic table is arranged in order of increasing atomic number (not mass). Also, elements with similar chemical properties are placed in the same vertical column.

Columns are called groups or families. Horizontal rows are called periods.

Valence Electrons – Electrons in the highest occupied energy level; maximum of 8. Elements in the same column have similar properties because they have the same number of valence electrons.

8 is the maximum number of valence electrons Electrons in the s and p orbitals of the outer shell are the valence electrons. 8 is the maximum number of valence electrons

Sodium: 1s22s22p63s1 Magnesium: 1s22s22p63s2 Fluorine: 1s22s22p5 The Octet Rule – Atoms tend to gain or lose electrons to have 8 e- Sodium: 1s22s22p63s1 Magnesium: 1s22s22p63s2 Fluorine: 1s22s22p5 Nitrogen: 1s22s22p3

Sodium: 1s22s22p63s1 Magnesium: 1s22s22p63s2 Fluorine: 1s22s22p5 The noble gases are chemically stable because they have a full outer energy level (valence). Atoms tend to gain or lose electrons to have 8 e- Sodium: 1s22s22p63s1 Magnesium: 1s22s22p63s2 Fluorine: 1s22s22p5 Nitrogen: 1s22s22p3

Electron configurations for Group 1 (valence e- underlined) 1s1 1s22s1 1s22s22p63s1 1s22s22p63s23p64s1 1s22s22p63s23p64s23d104p65s1 [Xe]6s1 [Rn]7s1

1s22s22p5 1s22s22p63s23p5 Get the idea?... Why is it called the Periodic Table of the Elements? The properties of the elements repeat going across each row.

Three broad classes of elements; metals, metalloids, nonmetals

Metals – good conductors of heat and electricity, shiny, most are solid at room temp (except Hg), malleable, ductile Nonmetals – not metals!, most are gases at room temp Metalloids – can show properties of both metals and nonmetals

Practice Explain why Mendeleev’s table was an accepted success. Why is the table of elements called the “periodic” table of elements? State 4 properties of metals. Explain the reason that elements in the same column have similar chemical properties? How can you tell if an elements is a metal, nonmetal or metalloid from the periodic table?

6. Name an element that is part of the Halogen family Alkali metal family Alkaline earth metal family Transition metals Inner transition metals Noble gas family 7. A horizontal row in the periodic table is called a _____.

8. Write the electron configuration for Nitrogen Chlorine Rubidium 9. How many valence electrons are in each element from question 8?

Section 2 – Periodic Trends Atomic size Ionic size (skip!) Ionization Energy Electronegativity

Atomic Size Atomic radius (pm) Atomic number

Atomic size generally decreases from left to right across a period. As Z increases across a row, the +/- electrical attraction increases, making the atom smaller. As Z increases down a group, another energy level is added to the atom which ‘shield’ the outer electrons from this nuclear attraction.

Ion – atom or group of atoms that has a positive or negative charge. Ions are formed when electrons are transferred between atoms.

Cation – ion with a positive charge. Anion – ion with a negative charge.

Metals tend to form cations Nonmetals tend to form anions

1st ionization energy = 520 kJ/mol 2nd ionization energy = 7297 kJ/mol Ionization Energy – energy required to remove an electron from an atom. lithium +1 ion lithium atom 1st ionization energy = 520 kJ/mol lithium ion Lithium +2 ion 2nd ionization energy = 7297 kJ/mol

1st ionization energy = 520 kJ/mol 2nd ionization energy = 7297 kJ/mol Ionization Energy – energy required to remove an electron from an atom. lithium +1 ion lithium atom 1st ionization energy = 520 kJ/mol lithium ion Lithium +2 ion 2nd ionization energy = 7297 kJ/mol

Ionization Energies of Some Common Elements Symbol First Second Third H 1312 He (noble gas) 2372 5247 Li 520 7297 11,810 Be 899 1757 14,840 C 1086 2352 4619 O 1314 3391 5301 F 1681 3375 6045 Ne (noble gas) 2080 3963 6276 Na 496 4565 6912 Mg 738 1450 7732 S 999 2260 3380 Ar (noble gas 1520 2665 3947 K 419 3096 4600 Ca 590 1146 4941

First ionization energy (kJ/mol) Atomic number

What does 1st ionization energy mean? Explain why the 2nd ionization energy of Li and Na is so much higher than the 1st ionization energy. Explain why the 1st ionization energy of Na is smaller than Li. Why are the ionization energies of the noble gases so large?

Electronegativity – tendency of an atom to attract electrons of another atom. Metals have low e-neg values, Nonmetals have high e-neg values

B<H<C Noble gases do not have e-neg values

Electronegativity Values for Selected Elements H 2.1 Li 1.0 Be 1.5 B 2.0 C 2.5 N 3.0 O 3.5 F 4.0 Na 0.9 Mg 1.2 Al Si 1.8 P S Cl K 0.8 Ca Ga 1.6 Ge As Se 2.4 Br 2.8 Rb Sr In 1.7 Sn Sb 1.9 Te I Cs 0.7 Ba Tl Pb Bi

Lesson 6 Practice How does the size of an atom change from left to right a) across a period? b) down a column? Give the explanation for question 1. What is an ion and how are they formed? Metals tend to form _____ ions and nonmetals tend to form _____ ions. Define Ionization Energy. Describe the trend in ionization energy in the periodic table.

Define electronegativity. Which atom is the a) most electronegative, b) least electronegative? Which atom has the highest ionization energy? How do electronegativity values differ between metals and nonmetals?

A little more for Chapter 6…

Lesson 6 Quiz Review Terms to know: valence electron, cation, anion, electronegativity, ionization energy (1st & 2nd)

Things to know: Metal, nonmetals, metalloids locations 4 properties of metals metals form cations, nonmetals form anions family names (alkali, alkaline earth, noble, halogens, transition and inner transition) electronegativity and ionization energy trends electron configurations (w/out aufbau diagram)

Possible Short Answer Questions: 1. Why was Mendeleev’s table an accepted success? 2. Why is the periodic table called the “periodic” table? 3. What causes elements in the same column to have similar chemical properties? 4. What is an ion and how are ions formed? 5. Why is the 2nd ionization energy of Na so much larger than the 1st ionization energy?

Energy levels can also be called electron shells