1. The Periodic Table and Periodicity
Chapter 14
The Periodic Table and Periodicity

2. Objectives Describe the origin of the periodic table
Explain relationships between electron configuration and locations of elements on the periodic table
Describe the nature of periods and groups of elements in the periodic table
Recognize periodicity by describing trends of those properties within periods and groups of elements

3. Origin of the Periodic Table
Dimitri Mendeleev- 1st to publish the classifcation of the elements that became the basis for the system used today.
Now called Periodic Table!

4. Mendeleev’s Periodic Table

5. How was the first periodic table arranged?
See page 360 in book
Arranged elements in order of their atomic masses
If no element had the expected properties to fit a particular place in the table, he left that place empty.

6. Periodic Table Mendeleev’s table was called the periodic table.
It was based on the original periodic law.
Periodic law- physical and chemical properties of elements were periodic functions of their atomic masses.

7. Where did the irregularities in this theory occur?
Look at your periodic table and try to identify where there would be a problem with organizing elements by their atomic mass.
Keep in mind, Mendeleev placed elements in groups based on similar properties, disregarding the fact that not all atomic masses were in order from least to greatest.

8. Consider Te and I What is the atomic mass of Te?
What is the atomic mass of I?
Can you think of the problem that Mendeleev faced?

9. Moseley and the Modern Periodic Law
In 1914, Moseley suggested that the elements in the periodic table be arranged in order of increasing atomic numbers instead of atomic masses.
Modern Periodic Law- the chemical and physical properties of the elements are periodic function of their atomic numbers.
Electron structure is related to atomic number, which does in fact determine the position of an element in the periodic table.

10. The Periodic Table and Electron Structure
Electron structure determines chemical properties which directly relates to electron configuration
For every member of a group or family, the electron arrangement of the valence shell is the same.
Valence shell- electrons found in the outer energy level.

11. Periodicity in Properties
Periodic table shows certain regularities in the properties of the elements
Members of a vertical group have similar properties
Why? They have the same number of valence electrons

12. Ion Atom or group of atoms that have a positive or negative charge.
*An atom is electrically neutral b/c it has equal #’s of protons and electrons*
Positive and negative ions form when electrons are transferred between atoms.

13. Cation vs. Anion + sign means lose electrons
Cation- ion with positive charge written as a # with a plus sign.
Anion- ion with a negative charge written as a # with a minus sign.
+ sign means lose electrons
- sign means gaining electrons

14. Ions
Metallic Elements- tend to form ions by losing one or more electrons, making them have a positive charge.
Nonmetallic elements- tend to form ions by gaining 1 or more electrons, making overall charge on atom negative.

15. Ion Game
*IONS ARE LAZY! They want to do whatever requires less energy!*
Remember the OCTET RULE- 8 valence electrons to be chemically happy!
Think about valence electrons…
Na: 1 valence electron
Options: Want to get to 0 or 8
Can lose 1 electron or gain 7 electrons
Losing 1 requires less energy!
Overall Charge: Na 1+

16. Isoelectronic Species
Those kinds of atoms or ions that have the same electron configuration
Example: many of the ions that form when atoms take on or give off electrons have the same electron configuration as the nearest noble gas…
N3- has the same configuration as ____?

17. Ionization Energy
Energy required to remove the most loosely held electron from the outer energy level of that atom in the gas phase.
Energy required to remove the first electron from a neutral atom is called first ionization energy.
Energy required to remove a second electron is called second ionization energy.

18. Periodic Trend in Ionization Energy
Increases from left to right
Why? As you increase # electrons, you need more energy to pull them away from the outer energy level.
Increases from bottom to top
Why? An element in a group has one additional energy level of electrons. There is a greater distance between the positive nucleus and the negative electrons= decrease in force of attraction.

19. Electronegativity
Measure of the ability of an atom of an element that is chemically combined with another element to attract electrons to itself.
Force of attraction that exists between an atom and a shared pair of electrons in a covalent bond
Electronegativity values are determined from bond energies.

20. Periodic Trend in Electronegativity
Increase left to right
Increase bottom to top
[Same as ionization energy]

21. Calculating Electronegativity Values
S-H
S-O
Two dots between each pair of the following symbols represent a pair of shared electrons. In which case is the electron pair more strongly attached to the sulfur atom?
See p Figure 14-16

22. Electron Affinity
Energy required to detach an electron from a singly charged negative ion.
Same trend as electronegativity
X- → X + e−

23. Atomic Radius
Closest distance to which one atom will approach another atom of any size under certain specified conditions

24. Atomic Radius
Unlike a ball, an atom doesn't have a fixed radius. The radius of an atom can only be found by measuring the distance between the nuclei of two touching atoms, and then halving that distance.

25. Trends in Atomic Radius
Leaving the noble gases out, atoms get smaller as you go across a period.
Why? As the atomic # increases, the increasing # of protons attracts the valence electrons more closely to the nucleus.
As you go down a group, atoms get larger.

26. Trends in Ionic Size
During reactions btwn metals and nonmetals, metal atoms tend to lose electrons and nonmetal atoms tend to gain electrons.
Size of cations/anions decrease from left to right
Size generally increases from top to bottom within groups

27. All Periodic Properties