sbdento

7+ Year Member
Nov 11, 2010
369
50
I don't know if my mind is going crazy from studying all day but I am confused on this problem:

Which statement(s) is false?

a. SiO2 and graphite are examples of ionic solids.
b. A solution of K2Cr2O7 is expected to be colored.
c. Mg has a thirds ionization E slightly higher than its second ionization E.
d. B and C
e. A and C

The book says E.

I understand why A is false, but why is C false? The third ionization E should be higher... right??
 
Dec 14, 2010
9
0
Status
Mg is in group II, meaning it has 2 valence electrons. After both of those electrons are ionized/removed/oxidized....then the next ionization energy has to break a new octet of electrons...think noble gases (which is incredibly stable). Thus to break into this new octet, the 3rd ionization energy has to be much higher (relatively) to the 1st two ionization energies in order to remove the electron.

just to make sure, isnt graphite/SiO2 a network solid?
 
OP
S

sbdento

7+ Year Member
Nov 11, 2010
369
50
SiO2 and graphite are network soilds.

So you think since they included "slightly" it makes it a false statement?
 
Jun 9, 2009
71
0
Cloud 9
Status
Pre-Dental
Mg is [Ne] 3s2
Mg2+ is 1s2 2s2 3p6

the third ionization energy is MUCH higher than the second ionization energy, because the two valence electrons are gone and now it's a filled configuration that will be disrupted.

so I would say "slightly" makes the statement false.
 
Dec 9, 2010
25
0
New York
Status
Pre-Dental
the word slightly is definitely what makes choice C false... the 1st ionization energy of Mg is 737, the 2nd ionization energy is 1450 and the 3rd is 7732 which is about 5 and a third times larger than the 2nd ionization energy
 
Dec 16, 2010
5
0
Status
Pre-Dental
Mg is in group II, meaning it has 2 valence electrons. After both of those electrons are ionized/removed/oxidized....then the next ionization energy has to break a new octet of electrons...think noble gases (which is incredibly stable). Thus to break into this new octet, the 3rd ionization energy has to be much higher (relatively) to the 1st two ionization energies in order to remove the electron.

just to make sure, isnt graphite/SiO2 a network solid?
graphite/SiO2 ithink covalent not ionic