1. Development of the Modern Periodic Table & Classification of the Elements
Sections 6.1 and 6.2

2. History of the Periodic Table
In the late 1790s, all the known elements were compiled in a list by Antoine Lavoisier.

3. History of the Periodic Table
In the late 1790s, all the known elements were compiled in a list by Antoine Lavoisier.
In all, there were only 23 elements on Lavoisier's list!!!

4. History of the Periodic Table
In the late 1790s, all the known elements were compiled in a list by Antoine Lavoisier.
In all, there were only 23 elements on Lavoisier's list!!!
Many more elements were identified in the 1800s due to the discovery of electricity, the invention of the spectrometer, and the industrial revolution.

5. History of the Periodic Table
In the late 1790s, all the known elements were compiled in a list by Antoine Lavoisier.
In all, there were only 23 elements on Lavoisier's list!!!
Many more elements were identified in the 1800s due to the discovery of electricity, the invention of the spectrometer, and the industrial revolution.
The industrial revolution led to the development of chemistry-based industries such as the manufacture of petrochemicals, soaps, dyes, and so on.
By 1870, about 70 elements were known to exist.

6. History of the Periodic Table
With so many elements, scientists were overwhelmed with trying to memorize all the properties of each individual element.
John Newlands, in 1864, proposed an element organization system based off of the idea of octaves.
He stated that the properties of the elements repeated every eighth element when they were arranged by increasing atomic mass, hence the name “octave”.

7. Electron Configuration Notation

8. History of the Periodic Table
In 1869, Lothar Meyer and Dmitri Mendeleev both developed an organization scheme that demonstrated a connection between atomic mass and the properties of elements.
But who is considered the father of the periodic table???
As we learned back in Chapter 4, Mendeleev left blank spaces in his periodic table and was able to predict the properties of elements that should occupy those blank spots.
Scandium, Gallium, Germanium

9. History of the Periodic Table
However, Mendeleev’s periodic table was not completely correct…
Several of the elements were found to be in the wrong order if they were arranged by increasing atomic mass.

10. History of the Periodic Table
However, Mendeleev’s periodic table was not completely correct…
Several of the elements were found to be in the wrong order if they were arranged by increasing atomic mass.
In 1913, Henry Mosley discovered that the nucleus of each element contains a unique number of protons.
Number of protons = Atomic Number
Therefore, once the elements were arranged in order of increasing atomic number, all of the elements were in the correct order.

11. History of the Periodic Table
Periodic Law – Statement that there is a periodic repetition of chemical and physical properties of elements when they are arranged in order of increasing atomic #.

12. The Modern Periodic Table
The modern periodic table is arranged in rows, known as ____________, and columns, known as ________________.
Elements in the same ______________ typically have similar chemical properties
Groups on the periodic table designated with an “A” are known as representative elements, since they posses a wide range of chemical and physical properties

13. The Modern Periodic Table
The groups designated with a “B” are known as the transition elements.
Classifying the elements:
Metals
Nonmetals
Metalloids (Semimetals)

14. Metals Metals are elements that are… Alkali metals –
Shiny
Solids at room temperature
Good conductors of heat and electricity
Malleable
Ductile
Alkali metals –
Alkaline earth metals –
Transition and Inner Transition Metals

15. Metals Metals are elements that are…
Shiny
Solids at room temperature
Good conductors of heat and electricity
Malleable
Ductile
Alkali metals – group 1A elements (but not H!)
Alkaline earth metals – group 2A elements
Transition and Inner Transition Metals – The group B elements on the periodic table

16. Metals
Transition and Inner Transition Metals – The group B elements on the periodic table
The Transition Metals are in the main portion of the periodic table
The Inner Transition Metals are found “underneath” the rest of the table
The 1st row is the Lanthanide Series
The 2nd row is the Actinide Series

17. Nonmetals Nonmetals are elements that are… Halogens – Noble Gases –
Brittle and dull when solids
Generally solids or gases at room temperature
Poor conductors of heat and electricity
Halogens –
Noble Gases –

18. Nonmetals Nonmetals are elements that are…
Brittle and dull when solids
Generally solids or gases at room temperature
Poor conductors of heat and electricity
Halogens – group 7A elements
Noble Gases – group 8A elements
The noble gases are extremely un-reactive

19. Metalloids
Metalloids (semimetals) are elements that have properties in common with both the metals and nonmetals!
The two most important metalloids are silicon and germanium

20. Organizing the Elements
Take a close look at the electron configurations for the following elements…
Hydrogen 1s1
Lithium 1s22s1
Sodium 1s22s22p63s1
Potassium 1s22s22p63s23p64s1

21. Organizing the Elements
They all have the same number of valence electrons!
Atoms in the same group have similar chemical properties because they have the same number of valence electrons!!!!!

22. Organizing the Elements
They all have the same number of valence electrons!
Atoms in the same group have similar chemical properties because they have the same number of valence electrons!!!!!
The principle energy level of the valence electrons determines the period that the element is in on the periodic table.

23. Organizing the Elements