Periodic Classification Flashcards
What is the law of triads?
The law of triads: in a group of three, the mass of mid element is equal to the average of the other two.
This was given Johann Dobereiner
Examples: (Li,Na,k), (Ca,Sr,Ba), (Cl,Br,I)
What is the law of octaves?
Law of Octaves: every 8th element’s the properties are similar to the first one.
Given by John Newland. It was applicable till Ca only
What were Lother Meyer’s findings?
He had plot of graph between atomic mass and physical properties noticing a periodic repetition
What all did Dimitri Mendeleev propose?
Periodic law: Properties of element are a periodic function of atomic mass.
Advantages;
1. first person to give tabular representation
2.corrected the mass of many elements
3. Included noble gases.
4. predicted the existence of few elements
Drawbacks:
1. no position for isotopes, hydrogen
2. be broke his own law ex. I and Te
3.No position for lanthanoids and actinoids
What does the modern periodic law state:
Modern periodic law: The chemical and physical properties of an element are a periodic function of their atomic mass.
Periods- 7
groups - 18
blocks -4
The general name for the following numbers:
0
1
2
3
4
5
6
7
8
9
nil
un
bi
tri
quad
pent
hex
hept
oct
enn
Name some semi-metals and Metalloids
Si, Te and Ge
What is reason for decrease of radius across the period and increases along the group?
This is due to increase in nuclear charge along the period and decrease in the group
What trends are found of ionization and electron gain enthalpy?
Both of them increase along the period
Ionization enthalpy
Energy required to loss an electron
Electron gain enthalpy
The amount of energy released or absorbed with electron is gained
Electronegativity
the tendency of an element to pull the shared pair of electron toward itself
What is the trend observed in electronegativity?
It increases along the period
What is the trend with metallic character?
It increases down the group
Why does Li and Be show anomalous behavior?
Due to their small size
large charge
and less number of orbitals
show covalent properties and diagonal relationship
