T2- s Block LP5 + LP6 + LP7

Question 1

Name alkaline earth metals.

Answer 1

Be (berylium), Mg (magnesium), Ca (calcium), Sr (strontium), Ba (barium), Ra (radium)

Question 2

Using flame test what colour we expect to see for Ca?

Answer 2

Orange-red

Question 3

Using flame test what colour we expect to see for Sr?

Answer 3

Crimson

Question 4

Using flame test what colour we expect to see for Ba?

Answer 4

Greenish yellow

Question 5

Using flame test what colour we expect to see for Ra?

Answer 5

Deep red

Question 6

Using flame test what colour we expect to see for Be and Mg?

Answer 6

No characteristic colour as saller size atoms and figher Z_eff mean a greater amount of energy is needed for excitation

Question 7

Why metallic bong is stronger for group 2 than 1?

Answer 7

As group 2 has larger number of electrons available

Question 8

Why Be is inert in air?

Answer 8

Because it is covered with BeO layer.

Question 9

Describe group 2 oxides.

Answer 9

Oxides of all metals can be formed directly by combination of the metals with oxygen except Ba.

Peroxides dtrong oxidising agents, docomposing to the oxide.

Thermal stabillities of peroxides increases down group. MgO₂ least stable.

Question 10

Describe group 2 nitrides.

Answer 10

Nitrides form through heating metal in an N₂ atmosphere. Nitriles will form the hydroxide and ammonia upon reaction with water.

Question 11

Describe group 2 hydrides.

Answer 11

Can be formed from direct reaction of the metal with H₂.

With the exceptiion of Be, all from ionic, saline hydrides that contain the H^- ion, these salts react vigorously with water.

Question 12

What is the structure of Be halides?

Answer 12

Solid state: polymeric chain, bonding based on sp³ hybridisation. As a result of sufficient electrons to invoke 2c-2e bonding

Vapou phase: forms dimer (sp²) and above 900 degrees linear monomers are formed (sp)

Question 13

What are quasilinear species?

Answer 13

It is a species where the calculated energy difference between a linear structure and a bent structure with a change of more than 20 degrees is less than 4 kJ/mol

Question 14

Wy do we get increase in preference for bent structures as we go down group 2 with halides?

Answer 14

It is a result of inverse polarisation and the participation of d atomic orbitals for Ca, Sr and Ba.

Question 15

What is inverse polarisation?

Answer 15

It occurs when the metal ion is polarisable and is polarised by F^-, Cl^-, or to a lesser extend Br^-.

Question 16

How participation od d orbitals affect bonding?

Answer 16

Be and Mg form only linear gaseous dihalides as these two metals only have s and p orbitals available for bonding and the best M-X orbital overlap is achieved from a linear molecule.

Ca, Sr or Ba the vacant d orbitals are available but can only overlap efficiently if the molecule is bent.

Out of phase combination of X—X orbitals only overlaps effieciently with d_yz if the molecule is bent.

Question 17

What does XRD stand for?

Answer 17

X-ray diffraction

Question 18

What does GED stand for?

Answer 18

Gas electron difraction

Question 19

Why we get different angles in metallocenes when going down group 2?

Answer 19

• Inverse polarisation
• d-orbutal involvement
• Increased van der Waals attraction between the ligands
• Small difference between linear and bent geometries

Question 20

How Gringnard reagend is generated?

Answer 20

By inserting Mg into a C-X bond

Question 21

Wht halogens can be used to make Gringard reagent?

Answer 21

I, Br, Cl (F is very unreactive)