History
- In 1860, only 60 elements were discovered.
- All the properties and numbers were published in a book.
- Scientist wanted an eaiser way to organize all the elements without the book.
- Because each chemist had different isotopes for each element they all had different masses for the elements.
- In 1860 all the Chemist met in congress to discuss and set the final atomic numbers, masses and properties of each of the 60 elements.
Dimitri mendeleev
- Russian Chemist.
- He was there during the process of writing the book of elements.
- He helped decide a way to organize the elements.
- He wrote the names of the elements on note cards and put their properties underneath each name.
- At first he started organizing them by their properties.
- By the end he organized them by INCREASING ATOMIC MASS.
IODINE/TELLURIUM
The problem with iodine and tellurium is that if they were put in the order of atomic mass then they don't fit with the columns they would be put in. Because Mendeleev thought they measured their mass wrong he put them in order of their properties instead of their atomic mass.
The problem with iodine and tellurium is that if they were put in the order of atomic mass then they don't fit with the columns they would be put in. Because Mendeleev thought they measured their mass wrong he put them in order of their properties instead of their atomic mass.
WHY PUT THE BLANK SPACES?
The Chemists put blank spaces on their periodic tables for future elements that have not been discovered yet.
The Chemists put blank spaces on their periodic tables for future elements that have not been discovered yet.
Henry Moseley
- British chemist
- He Fixed the problems with Mendeleev's table
- He rearranged elements according to atomic NUMBER instead of mass.
- Solved the Iodine/tellurium problem
- Created the periodic law
- Periodic Law- the physical and chemical properties of the elements are a function of their atomic numbers ( when elements are put in order of atomic number, then they fit into a certain column that has certian characteristics like reacts with water.
Groups and what's in them
Group 1 - Alkali Metals
All have only one valence electron
Only HYDROGEN is NOT clasified as an alkali metal
Group 2- Alkaline Earth Metals
All have 2 valence electrons
Harder and denser than group 1 but not as reactive
Still TOO reactive to be found free in nature
Groups 3-12 - Transition Metals
Not as reactive as groups 1 & 2
Most have 2 valence electrons ( except group 11 they have one )
You will be told in a problem if a transition metal has more or less than 2 valence electrons
P-Block Elements
8 metals to the left of the "Staircase" ( Al, Ga, In, T, Sn, Pb, Bi, Po )
8 metalloids on the "staircase" ( B, Si, Ge, As, Sb, Te, Po, At )
The rest are non- metals ( to the right of staircase )
Group 17 - Halogens
7 valence electrons
Most reactive of the NON-METALS
Fluorine is teh MOST REACTIVE OF ALL ELEMENTS
when nonmetal(s) combines with a metal, it produces a salt ( Na + Cl= NaCl )
Group 18- Noble Gases
8 valence electrons
Helium is the ONLY exception
Least reactive of all the elements
No need to form compounds because it's outershell is full.
Rare earth Metals
Lanthanoids
elements 58-71
2 valence electrons
Actinoids
elements 90-103
man made
most are radioactive
To know the number of valence electrons use the trick with the groups…Group number is the number of electrons except for 3-12 in which they have 2 ve-, and for groups 13-18 subtract 10 from the group number to get the number of ve-
All have only one valence electron
Only HYDROGEN is NOT clasified as an alkali metal
Group 2- Alkaline Earth Metals
All have 2 valence electrons
Harder and denser than group 1 but not as reactive
Still TOO reactive to be found free in nature
Groups 3-12 - Transition Metals
Not as reactive as groups 1 & 2
Most have 2 valence electrons ( except group 11 they have one )
You will be told in a problem if a transition metal has more or less than 2 valence electrons
P-Block Elements
8 metals to the left of the "Staircase" ( Al, Ga, In, T, Sn, Pb, Bi, Po )
8 metalloids on the "staircase" ( B, Si, Ge, As, Sb, Te, Po, At )
The rest are non- metals ( to the right of staircase )
Group 17 - Halogens
7 valence electrons
Most reactive of the NON-METALS
Fluorine is teh MOST REACTIVE OF ALL ELEMENTS
when nonmetal(s) combines with a metal, it produces a salt ( Na + Cl= NaCl )
Group 18- Noble Gases
8 valence electrons
Helium is the ONLY exception
Least reactive of all the elements
No need to form compounds because it's outershell is full.
Rare earth Metals
Lanthanoids
elements 58-71
2 valence electrons
Actinoids
elements 90-103
man made
most are radioactive
To know the number of valence electrons use the trick with the groups…Group number is the number of electrons except for 3-12 in which they have 2 ve-, and for groups 13-18 subtract 10 from the group number to get the number of ve-
Information was presented in class.