Main Group Chemistry Flashcards
(41 cards)
What is the difference between second and third period elements
The second period elements are often anomalous in their behaviour, whereas the third period elements are more representative of the group
Why do 2nd period elements have anomalous behaviour
- Small size and high electronegativity
- Maximum of four covalent bonds (no d orbitals for bonding)
- More common occurrence of multiple bonding (good pi overlap of 2p orbitals)
What happens proceeding down a group
Metallic behaviour increases, positive oxidation states are prevalent
True or false: all halogens can form only one oxidation state (-1)
False. Only fluorine forms (-1) oxidation state because it is the most electronegative Halogen
Why are expanded octets and corresponding hybridization not observed in 2nd row elements
Because valance orbitals of 2nd row elements are restricted to 2s and 2p orbitals and only hybridization scheme is restricted to four covalent bonds
Why is it more common to see multiple bonding in 2nd row elements than 3rd row and beyond?
Because in 2nd period elements the 2p orbitals are closer in proximity to each other which makes pi bonding more effective
Properties of alkali metals
- unusually soft
- have lower melting/boiling points & densities
*this is because of their large ionic size and ns^1 valence electron configuration
Why are crystal structures easily deformed in alkali metals
The single valence e- is not held tightly and the metallic bonding in the solid is weak
Are alkali metals good reducing or oxidizing agents
Powerful reducing agents
Properties of alkali earth metals
Harder & higher melting than alkali metals, somewhat less reactive
What is the use of alkali earth compound CaCO3
Calcium carbonate is heated to obtain calcium oxide (lime)
Has essential roles in steel making, water treatment, used to make glass, whiten paper, and neutralize acidic soil
What is unique about BE
- unreactive in air and water
- BeO is an amphoteric oxide
- have strong covalent character and conduct electricity poorly
Why is gallium smaller than aluminum
Because of the presence of an intervening 3D sub shell, which increases Zeff
What are properties of boron
- metalloid with a covalent network structure
- black, hard, high mp
What is the molecular formula of boron
B2H6
What are common applications of boron
Pyrex glass, sodium perforate as colour safe bleach, and boric acid as cockroach insecticide
What does the three-center-two-electron bond illustrate
The electrons can be delocalized over more than two atoms
What is the major ore of aluminum and how is it extracted
Bauxite (Al2O3)
Converting Al2O3 to Al takes place through a reduction process followed through by electrolysis
What are applications of aluminium
Aluminium forms alloys that are strong & light weight & resistant to corrosion.
Aircraft, bicycles, appliances
What are pnictogens
Group 15 elements
What do nitrogen and phosphorus do
Combine with many non-metals to form covalent compounds and attain oxidation states from -3 to +5
What is nitrogen used as
A cryogen, (low temp refrigerant) to store temp sensitive samples
What is white phosphorous
An allotrope of phosphorus
White, waxy, highly toxic solid with a low melting point (44c) and glows faintly
Narrow bond angles are incompatible with any localized bonding scheme so it is highly reactive
What is red phosphorus
Red, non-toxic solid with a high melting point
Bonds are not strained so it is less reactive than white phosphorous. Used to manufacture meth
