Chapter 6 The Periodic Table and Periodic Law

Warm-Up 1. Write the electron configurations for the following:

• Sn (50)

• S (16)

• K (19)

• Ti (22)

2. The half-life of Zn-71 is 2.4 minutes. If one had 100.0 g at the beginning, how many grams would be left after 7.2 minutes has elapsed?

Warm-Up 1. Write the electron configurations for the following:

• Sn (50) • 1s22s22p63s23p63d104s24p64d105s25p2

• S (16) • 1s22s22p63s23p4

• K (19) • 1s22s22p63s23p64s1

• Ti (22) • 1s22s22p63s23p64s23d2

2. The half-life of Zn-71 is 2.4 minutes. If one had 100.0 g at the beginning, how many grams would be left after 7.2 minutes has elapsed?

• 7.2 / 2.4 = 3 half-lives • 0 - 100g

• 1 – 50 g

• 2 – 25 g

• 3 – 12.5 g

Development of the Modern Periodic Table • The Periodic Table will help you organize chemistry

knowledge

• The table is arranged by the following: • Groups (columns)

• AKA families

• Periods (rows)

Groups and Families Periodic Tables

Groups and Families Periodic Tables

History of the Periodic Table’s Development

Antoine Levoisier • 1790s compiled a list of

known elements. • 23 elements on the list.

• Elements included gold, silver and other elements known since prehistoric times.

History of the Periodic Table’s Development 1800s • Knowledge explosion due to advances in scientific technology

• Electricity allowed scientists to break down compounds into their basic elements

• Spectrometer was used to identify newly isolated elements

• Industrial Revolution • Many new chemistry-based industries (petrochemicals, soaps, dyes, etc.)

• 1860s - 1870s • Chemists agreed to use the Atomic Masses were standardize

• Over 70 Elements Known

History of the Periodic Table’s Development John Newlands • Developed the law of

octaves • Every 8 elements, the

properties repeat • Called a period

• Based on atomic mass

• Other scientists thought the naming of “Law of Octaves” to be unscientific as it was based on music

History of the Periodic Table’s Development, Cont. Meyer, Mendeleev and Moseley • Meyer and Mendeleev

• Understood the correlation between atomic masses and elemental properties

• Mendeleev organized the first periodic table

• Left blank spaces where undiscovered elements would go

• Able to predict properties of yet unknown elements, based on observed trends

• Periodic Table not Fully Correct

History of the Periodic Table’s Development, Cont. Meyer, Mendeleev and Moseley • Moseley

• Reorganized the periodic table developed by Mendeleev

• Included newly found elements

• Discovered each element contains a unique number of elements in their nuclei

• Rearranged elements by atomic number, not atomic mass

• Periodic Law: Periodic repetition of chemical and physical properties that are arranged by increasing periodic number

Modern Periodic Table

Groups and Periods • Columns

• Groups/Families of elements that have similar properties

• Rows • Periods of elements that

repeat properties

• Total of 7 periods

Modern Periodic Table

Groups and Periods • Columns

• Groups/Families of elements that have similar properties

• Total 18 Groups

• Rows • Periods of elements that

repeat properties

• Total of 7 periods

Modern Periodic Table Classifying Elements • 1A) Alkali Metals

• 2A) Alkaline Earth Metals

• Both 1A and 2A are chemically Reactive with Alkali being the most reactive of the two

• 3A) Boron Family

• 4A) Carbon Family

• 5A) Nitrogen Family

• 6A) Oxygen Family

• 7A) Halogen / Fluorine Family

• 8A) Noble Gas / Helium Family

Modern Periodic Table Classifying Elements • The B Group are the Transition Elements

Organizing the Elements by Electron Configuraton Valence Electrons and the Period • Period denotes the highest

level energy level

Valence Electrons and Group/Families • Group denotes the number

of valence electrons

S, P, D and F Block Elements S, P • S

• As S-Orbitals holds maximum of 2 electrons, spans 2 groups

• P • As P-Orbitals hold

maximum of 6 electrons, spans 6 groups

D, F • D

• Contains transitions metals and is the largest block of elements

• Characterized by completely filled S orbitals and increasingly filled D orbitals

• As D-Orbitals hold 10 electrons, spans 10 groups

• F • Contains inner transition metals

• As F-Orbitals hold 14 electrons, spans 14 groups

Principal Energy Levels Period Principal

Energy Level Element

1 n = 1 He, H 2 n = 2 Li, Be, B, C, N,

O, F, Ne 3 n = 3 Na, Mg, Al, Si,

P, S, Cl, Ar 4 n = 4 K, Ca, Ga, Ge,

As, Se, Br, Kr 5 n = 5 Rb, Sr, In, Sn,

Sb, Te, I, Xe 6 n = 6 Cs, Ba, Ti, Pb,

Bi, Po, At, Rn 7 n = 7 Fr, Ra

Principal Energy Level: The energy level denoted by the principal quantum number n. The first element in a period introduces the new principal energy level. Principal Energy Levels are broken down into sub-levels (S, P, F, D)

Bohr Model of the Atom

How to Draw a Bohr Model 1. Draw the nucleus.

2. Write element symbol, the number of neutrons and the number of protons in the nucleus.

3. Draw the first energy level.

4. Draw the electrons in the energy levels according to the rules. Make sure you draw the electrons in pairs.

5. Keep track of how many electrons are put in each level and the number of electrons left to use.

Bohr Model of the Atom, Continued

Rules for Bohr Energy Levels • Level 1: Holds a Maximum of 2e

• Level 2: Holds a Maximum of 8e

• Level 3: Holds a Maximum of 18e

• Level 4: Holds a Maximum of 32e.

Guided Practice on Bohr Models

Draw a Bohr Model for C • Element Symbol: C

• Atomic Number: 6

• Atomic Mass: 12

• Protons: _____________

• Neutrons: ______________

• Electrons: ______________

• Number of Energy Shells: ______________

• Number of Valence Electrons (Outer Shell): ____________________________

C

Guided Practice on Bohr Models Draw a Bohr Model for C • Element Symbol: C

• Atomic Number: 6

• Atomic Mass: 12

• Protons: 6

• Neutrons: 6

• Electrons: 6

• Number of Energy Shells: 2

• Number of Valence Electrons (Outer Shell): 4

C Protons: 6 Neutrons: 6

• Element Symbol: C

• Atomic Number: 6

• Atomic Mass: 12

• Protons: 6

• Neutrons: 6

• Electrons: 6

• Number of Energy Shells: 2

• Number of Valence Electrons (Outer Shell): 4

Guided Practice on Bohr Models Draw a Bohr Model for C

C Protons: 6 Neutrons: 6

Warm-Up 1.Draw the Lewis Dot Structure for Sodium

2.Draw the Lewis Dot Structure for Flourine

3.Draw the Bohr Model of an Atom for Carbon

4.Draw the Bohr Model of an Atom for Silicon

Periodic Trends Atomic Radius • Atomic Radius

• Metals: Atomic radius is half the distance between adjacent nuclei in a crystal of the element

• Elements that occur as molecules: Half the distance between nuclei of identical atoms that are chemically bonded together.

• Period Trends:

• Decrease from Left to Right

• More valence electrons without higher level orbitals means a higher nuclear charge, condensing the atomic radius

• Group Trends:

• Increase from top to bottom

• Increase in electrons, plus the addition of higher level orbitals.

Periodic Trends

Periodic Trends Ionic Radius • Ion: Atom or bonded group of atoms that has either a positive or negative charge

• They have either gained or lost an electron

• Ionic Radius: Atomic radius of an ion

• When ions are formed, it is ALWAYS valence electrons that are either gained or lost

• When lost (creating a positive CATion), the radius becomes smaller as are either fewer electrons or a completely empty orbital shell

• When an electron is gained (creating a negative ANion), the radius becomes larger as there are both more electrons and they may be within higher level orbital shells.

Periodic Trends Ionic Radius • Period Trends:

• Increase from Left to Right

• Left-side of the table form smaller positive ion (CATions)

• Right-side of the table form larger negative ions (ANions)

• Group Trends:

• Increase from top to bottom

• Increase in electrons, plus the addition of higher level orbitals.

Periodic Trends

Periodic Trends Ionization Energy • Ionization Energy: Energy required to remove an electron from a

gaseous atom.

• First Ionization Energy: The energy required to remove the first electron from an atom

• Period Trends:

• First ionization energies increase from left to right, due to the increased nuclear charge (more protons = stronger charge) on the valence electrons

• Group Trends:

• First ionization energies decrease from top to bottom on groups, due to the valence electrons being further away from the nucleus in higher level shells.

Periodic Trends

Octet Rule • Remember “Eight is Great”

• Atoms tend to gain, lose or share electrons in order to get to 8 valence electrons

Periodic Trends Octet Rule and Electron Configuration • When gaining or losing an electron (creating Anions and

Cations), the electron configuration needs to change

• If losing an electron: remove it from the top-level orbital first • Li = 1S22S1

• Li+ = 1S2

• If gain an electron: add it to the top level orbital first and if that is full, add the next level orbital • F = 1S22S22P5

• F- = 1S22S22P6

Periodic Trends Electronegativity • Electronegativity: Indicates the relative ability of an element

to attract electrons into a chemical bond

• Period Trends:

• Increase as you move left-to-right

• Group Trends:

• Decrease as you move down a group

• Lowest Electronegativity Energies in lower left

• Highest Electronegativity Energies in upper right