Sorry, that is incorrect.

The only correct answer is: 801 , 2427 , 3660 , 25,026

• 1086 , 2353 , 4621 , 6223 is incorrect because this does not show a large increase for the fourth ionization, so it is not in group 3.
• 900 , 1757 , 14,849 , 21,007 is incorrect because it shows a large increase for the third ionization, so it is in group 2.
• 578 , 1817 , 2745 , 11,578 is incorrect because it is a group 3 element as it has a large increase for the fourth ionization, but it has a first ionization energy that is lower than that of the correct option. So it is below it in Group 3. So it cannot be Boron.

Sorry, that is incorrect.

The only correct answer is: quantum shells

• Atoms: This is incorrect because atomic emission spectroscopy does not provide evidence for the existence of atoms.
• Electrons: This is incorrect because atomic emission spectroscopy does not provide evidence for the existence of electrons.
• Isotopes: This is incorrect because the evidence for isotopes is provided by mass spectroscopy.

Sorry, that is incorrect.

The only correct answer is: 12 

• 5 is incorrect because this is the number of electrons in the 3p orbitals of the chlorine atom
• 6 is incorrect because this is only the number of electrons in the 3p orbitals of the chloride ion
• 18 is incorrect because this is the total number of electrons in the chloride ion, not just those in the p orbitals.

Sorry, that is incorrect.

The only correct answer is: 801 , 2,427 , 3,660 , 25,026 , 32,828

• 738 , 1,451 , 7,733 , 10,541 , 13,629 is incorrect because it is typical of group 2 elements.
• 1,086 , 2,353 , 4,621 , 6,223 , 37 832 is incorrect because it is typical of group 4 elements.
• 1,402 , 2,856 , 4,578 , 7,475 , 9 445 is incorrect because it could be for group 5,6,7,8 or transition elements.

Sorry, that is incorrect.

The only correct answer is: $Na^{+}$ and $Mg^{2+}$

• $N^{3-}$ and $Cl^{-}$ is incorrect because the chloride ion has an extra shell of electrons compared to the nitride ion.
• $O^{2-}$ and $S^{2-}$ is incorrect because the sulfide ion has an extra shell of electrons compared to the oxide ion.
• $Na^{+}$ and $K^{+}$ is incorrect because the potassium ion has an extra shell of electrons compared to the sodium ion.

Sorry, that is incorrect.

The only correct answer is: $N^{3-}$

• $O^{2-}$ is not correct because oxygen has more protons to exert an attractive force to reduce the ionic radius
• $Na^{+}$ is not correct because sodium has more protons to exert an attractive force to reduce the ionic radius
• $Al^{3+}$ is not correct because aluminum has more protons to exert an attractive force to reduce the ionic radius

Sorry, that is incorrect.

The only correct answer is: hexagonal rings within a layer

• layers with each atom bonded to four others is not correct because, in the layers of graphite and graphene, the carbon atoms are bonded to three other carbon atoms and not four.
• hexagonal and pentagonal rings within a layer is not correct because graphite and graphene do not have pentagonal rings within their layers
• a three-dimensional structure is not correct because graphene is a two-dimensional structure consisting of a single layer

Sorry, that is incorrect.

The only correct answer is: $CH_{3}CH_{2}CH(OH)CH_{2}CH_{3}$

• $CH_{3}CH(OH)CH(CH_{3})_{2}$ is not correct because it will not form pent-2-ene
• $CH_{2}(OH)CH_{2}CH_{2}CH_{2}CH_{3}$ is not correct because it will only form pent-1-ene
• $CH_{3}CH_{2}CH_{2}CH(OH)CH_{3}$ is not correct because $CH_{3}CH(OH)CH_{2}CH_{2}CH_{3}$ will also form Pent-1-ene

Sorry, that is incorrect.

The only correct answer is: carbon particulates

• carbon particulates is incorrect because oxides of nitrogen are not black solids
• oxides of sulfur is incorrect because oxides of sulfur are not black
• unburnt hydrocarbons is incorrect because unburnt hydrocarbons are not black solids

Sorry, that is incorrect.

The only correct answer is: ions

• only carbocations is not correct because both anions and cations are produced
• only free radicals is not correct because homolytic fission produces free radicals
• free radicals and ions is not correct because homolytic fission produces free radicals and heterolytic fission also produces anions