Two elements A and B contain 13 and 8 protons respectively. If the number of neutrons in them happen to be 14 and 8 respectively; the formula unit mass for the compound between A and B unit would be:
Answers
Given : Element A has 13 Protons
We know that : The Number of Protons in the Nucleus of an Element is it's Atomic Number.
⇒ The Atomic Number of Element A is 13
⇒ The Electronic Configuration of Element A is 1s² 2s² 2p⁶ 3s³
We know that : Every Element tries to reach its Nearest Stable Electronic Configuration by either Gaining the Electrons or Loosing the Electrons.
We can Notice that : The Nearest Stable Electronic Configuration for Element A is Neon - 1s² 2s² 2p⁶.
So, The Element A always tries to loose its 3 Electrons in the 3s Subshell in order to obtain the Stable Electronic Configuration of Neon.
Hence, The Cation formed by Element A is A³⁺
Given : Element B has 8 Protons
⇒ The Atomic Number of Element B is 8
⇒ The Electronic Configuration of Element B is 1s² 2s² 2p⁴
We can Notice that : The Nearest Stable Electronic Configuration for Element B is Neon - 1s² 2s² 2p⁶
So, The Element B Always Tries to Gain 2 Electrons from Other Elements in order to obtain the Stable Electronic Configuration of Neon.
Hence, The Anion formed by Element B is B²⁻
Now : A and B both discussed among themselves and finally came to a Conclusion that they want combine with each other and form a Compound. So, that they both experience the feeling of having a Stable Electronic Configuration. They Combine Each Other by forming an Ionic Bond between themselves.
We know that : In an Ionic Bond Net Charge should be Zero. Right now if they Combine, The Net Charge will be 3 - 2 = +1
So, In order to Make the Net Charge on the Compound formed to be Zero. The Positive Charge on the Compound formed and The Negative Charge on the Compound formed should be Same. So, that when we add both the Charges, We would get a Zero. This can be Done by Adding Required Number of respective Same Element's Cations and Anions to the Cation and Anion which want to form a Compound.
The Least Common Multiple of 3 and 2 is 6
So, We need add One More Cation of A³⁺ to the Cation A³⁺, So the Combined Charge on both of them is (3 + 3) = +6
⇒ The Number of Atoms of Element A in the Compound = 2
We need add Two More Anions of B²⁻ to the Anion B²⁻, So the Combined Charge on both of them is (- 2 - 2 - 2)= -6
⇒ The Number of Atoms of Element B in the Compound = 3
⇒ The Formula of the Compound formed by A and B is A₂B₃
Given : The Number of Neutrons in A = 14
We know that : Atomic Mass is the Sum of Protons and Neutrons present in the Nucleus of an Atom.
⇒ The Atomic Mass of Element A = (13u + 14u) = 27u
Given : The Number of Neutrons in Element B = 8
⇒ The Atomic Mass of Element B = (8u + 8u) = 16u
Where 'u' is the unified mass which is equal to 1.66 × 10⁻²⁷ kg
We found that : The Formula of the Compound is A₂B₃
⇒ The Formula Unit Mass of the Compound : (27 × 2)u + (16 × 3)u
⇒ The Formula Unit Mass of the Compound : (54u + 48u) = 102u
⇒ The Formula Unit Mass for the Compound between A and B is 102
Answer:
Two elements A and B contain 13 and 8 protons respectively. They will have 3 and 6 valence electrons respectively and will form A
3+ and B 2− ion respectively.
The atomic mass of A =13+14=27
The atomic mass of B 8+8=16
The formula unit mass for the compound between A and B unit would be 2(27)+3(16)=102
Hence, the option (C) is the correct answer.