1. History of the Periodic Table
Chemistry I

2. Bell Work
It’s always a good idea to have organization in your life. What are some things you keep organized to make life easier?

3. Dmitri Mendeleev
Him and Lother Meyer first identified a way for classifying the elements in 1869
Mendeleev published his scheme first and was more successful at demonstrating its value, so he is given more credit
Noticed when organizing elements by increasing atomic mass, he could see a periodic repetition of their properties

4. Dmitri Mendeleev
Mendeleev sometimes broke the pattern of organizing them by atomic mass so elements of similar properties can be kept in the same columns
Predicted a new element – ekasilicon that had very similar properties to the later discovered germanium!

5. Henry Moseley In 1913, Moseley reorganized atoms by atomic number
This kept all elements organized by properties, but deals with the few inconsistencies where mass number didn’t increase along with atomic number
Periodic Law – when elements are arranged in order of increasing atomic number, their physical and chemical properties show a periodic pattern

6. GROUPS AND PERIODS
Group – column down a periodic table, also called families
Period – horizontal rows in the periodic table
Groups normally referred to as 1A -8A, skipping over the transition metals
Transition metals are 1B to 8B
Numbered 1-18 also

7. Groups (Columns) of the Periodic Table
Alkali metals – group 1
Very reactive
Alkaline earth metals – group 2
Slightly less reactive
Halogens – group 17
Often react with alkali metals to form salts
Noble Gases – Group 18
Very unreactive gases

8. Periodic Table

9. s, p, d, and f block elements
s-block elements
Groups 1 and 2
Metals
Electron configurations all end in s
p-block elements
Groups 13-18
Contain metals, nonmetals, and metalloids
Electron configurations all end in p
d-block elements
Transition metals
All end in d
f-block elements
Lanthanides and actinides
All end in f

10. Valence Electrons
Core Electrons – “inner” electrons, do not participate in bonding
Valence Electrons – “outer” electrons, electrons in the highest occupied energy level
number of valence electrons largely determines the chemical properties of an element
So which electrons in an electron configuration are core and valence?
Be – [He] 2s2 P – [Ne] 3s2 3p3
Core Valence Core Valence

11. So how do I find this valence number?
The valence electrons an atom has is the same as its group number for a representative (main group) element

12. So how do I find this valence number?
So how many valence electrons would Na have? 1
Iodine? 7
Krypton? 8