Sec. 4.4- Periodic Table

The First Periodic Table Elements organized on the periodic table 1800s- As more and more elements discovered, a way of organizing them became more important

Mendeleev- published periodic table where elements placed in order of increasing atomic mass Created “element cards”- inspired by favorite card game solitaire Element cards- contained element name, atomic mass, basic properties, and some compounds the element formed

When Mendeleev placed elements in order of increasing atomic mass, he noticed that certain properties repeated themselves These properties repeated in a predictable pattern- also called a “periodic” pattern Mendeleev then placed elements with similar properties in the same vertical column- called groups/families

Mendeleev was forced to leave holes in his periodic table- these holes were left for undiscovered elements Due to the organization of his table, Mendeleev was able to predict the properties of these undiscovered elements Once the elements that fit into these holes were discovered, they matched the properties Mendeleev predicted almost perfectly

The Modern Periodic Table The modern periodic table is organized by increasing atomic number What was atomic number? In general, the modern table is very similar to Mendeleev’s table, with only a few differences Only a couple of elements were switched

Generally speaking, elements increase in mass as you move from left to right Can you pick out any that break this trend?

Horizontal rows= periods Vertical columns= groups/families Elements in same family have very similar properties- react in similar ways The periods at the bottom (Lanthanides and Actinides) are actually meant to fit into the table- just separated for convenience

Group 1- Alkali metals Group 2 – Alkaline earth metals Groups 3-12 Transition metals Group 13 -15 no name! Group 16- Chalcogens Group 17 – Halogens Group 18- Noble Gases Actinides Lanthanides

Some Group Characteristics Alkali Metals- all have 1 valence electron Hydrogen is at the top of this group but is not an alkali metal- it is a nonmetal Why is it even in this group? Soft, gray metals- all violently reactive with water Alkaline Earth Metals- all have 2 valence electrons Also fairly reactive with water, but not as much as the alkali metals

Group 13- Family beginning with Boron- all have 3 valence electrons Group 14- Family beginning with Carbon- all have 4 valence electrons Group 15- Family beginning with Nitrogen- all have 5 valence electrons Chalcogens- Family beginning with Oxygen- all have 6 valence electrons, slightly reactive

Halogens- Family beginning with Fluorine- all have 7 valence electrons- most reactive group of nonmetals Noble Gases- All have full valence shells, He has 2, the rest have 8 valence electrons, colorless, ordorless gases, highly unreactive

Table with Lanthanides and Actinides

Electron Configuration and the Periodic Table Due to the arrangement of the modern periodic table, there is a perfect pattern found that can be used for electron configuration Atomic number = number of….? For neutral atoms, atomic number would also be the same as what?

Each period= energy level Once at the end of the period (Noble Gases) energy level is full As you move from left to right, the number of electrons increases (from one element to another, it increases by 1 electron)

For elements in the same family, the number of valence electrons is the same What were valence electrons? Due to this pattern, we are able to use the periodic table as a “map” for electron configuration

The periodic table is the answer key for electron configurations Each section of the periodic table corresponds to a subshell type s section- first two columns- how many electrons can an s subshell hold? (How many orbitals- electrons?)

p section- contains 6 columns- how may electrons can a p subshell hold? d section- contains 10 columns- how may electrons can a d subshell hold? f section- contains 14 columns- how may electrons can a f subshell hold?

s subshell section- begins in level 1- begins with 1s p subshell section- begins in level 2- begins with 2p d subshell section- begins in level 3- begins with 3d f subshell section- begins in level 4- begins with 4f

Get out periodic tables- we’re going to label them to use them as keys for electron configuration!