1. The Modern Periodic Table

2. Early Periodic Table – Atomic Number
In 1913 Henry Mosley discovered that each element contained a unique number of protons in the nuclei
Arranged elements in order of atomic number.
Resulted in a clear periodic pattern of properties.

3. Periodic Law
There is a periodic repetition of chemical and physical properties of elements when arranged in increasing atomic number (increasing number of protons) called the periodic law

4. Representative Elements
Modern Periodic Table
Organized in columns called groups or families
Rows are called periods
Group A – representative elements (1A-8A)
Group B - transition elements (1B-8B)
Representative Elements
(Group A)
Representative Elements
(Group A)
Transition Elements
(Group B)

5. Classification of Elements
Three classifications for elements metals, nonmetals, and metalloids (semimetals).

6. Metals Properties of Metals shiny, smooth, solids (except mercury)
Good conductors of heat and electricity
High densities
High melting and boiling points
Malleable – bended or pounded into sheets
Ductile – drawn into wires

7. Groups of Metals Alkali metals – group 1A except H
Alkaline earth metals – group 2A
Alkali metals and alkaline earth metals are chemically reactive
Transition metals – group B elements
Inner transition metals
Lanthanide
Actinide

8. Metals Alkali Metals Alkaline Earth Metals Transition Metals
(B group elements)
Alkali Metals
Alkaline Earth Metals
Inner Transition Metals

9. Organizing by Electron Configuration
Group number for group A elements represents the number of valence electrons
Atoms in the same group have similar chemical properties because they have the same number of valence electrons

10. Alkali Metals Electron configurations for alkali metals
Lithium 1s22s [He]2s1
Sodium s22s22p63s [Ne]3s1
Potassium 1s22s22p63s23p64s [Ar]4s1
Rubidium 1s22s22p63s23p64s23d104p65s1[Kr]5s1
What do the four configurations have in common?
They have a single electron in their outermost energy level
They all have one valence electron, thus similar chemical properties

11. Alkaline Earth Metals Electron configuration for alkaline earth metals
Beryllium [He]2s2
Magnesium [Ne]3s2
Calcium [Ar]4s2
Strontium [Kr]5s2
All alkaline earth metals have two valence electrons, thus similar chemical properties.

12. Question Time What are representative elements?
What are Group B elements called?
What are the three classifications for elements?
What are the characteristics of metals?
Where are the alkali metals and alkaline earth metals located?
Where are transition metals located?
What are the inner transition metals?
How many valence electrons do alkali metals and alkaline earth metals have?

13. Nonmetals Gases or brittle, dull looking solids
Poor conductors of heat and electricity
Usually have lower densities, melting point, and boiling point than metals.
Groups of nonmetals
Halogens 7A
Noble gases 8A
sulfur

14. Nonmetals
Noble Gases
Halogens

15. Noble Gases Noble gases – Group 8A
Called inert gases because they rarely take part in a reaction
He – 1s2
Ne – 1s22s22p6
Ar – 1s22s22p63s23p6
Kr - 1s22s22p63s23p63d104s24p6
Because noble gases have completely filled s and p sublevels, they do not react with other elements

16. Metalloids (Semimetals)
Physical and chemical properties similar to both metals and nonmetals
They are metallic-looking brittle solids
Relatively good electrical conductivity.
Used in glasses, alloys, and semiconductors
The six elements commonly recognized as metalloids are boron, silicon, germanium, arsenic, antimony, and tellurium. Polonium and astatine are sometimes classified as metalloids

17. Metalloids (Semimetals)

18. Question Time What are the properties of nonmetals?
Where are halogens and noble gases found?
Why are noble gases unreactive (inert)?
What are the properties of metalloids (semimetals)?
Which six elements are most commonly known as metalloids (semimetals)?