Question

1. which of the following is the correct representation of the electron configuration of oxygen in its ground state?
2. a 100.00 - gram sample of naturally occurring boron contains 19.78 grams of boron - 10 (atomic mass = 10.01 atomic mass units) and 80.22 grams of boron - 11 (atomic mass = 11.01 atomic mass units). which numerical setup can be used to determine the atomic mass of naturally occurring boron?

(a) (0.1978)(10.01)+(0.8022)(11.01)
(b) (0.1978)(11.01)+(0.8822)(10.01)
(c) (0.1978)(10.01)×(0.8022)(11.01)
(d) (19.78)(0.1001)×(80.22)(0.1101)

Explanation:

Question 21

According to Hund's rule, electrons fill degenerate orbitals (same - energy orbitals) singly as far as possible before pairing up. Oxygen has 8 electrons. The electron configuration is \(1s^{2}2s^{2}2p^{4}\). In the \(2p\) sub - shell (three degenerate \(p\) orbitals), first, three electrons occupy each \(p\) orbital singly, and then the fourth electron pairs up.

The formula for the average atomic mass of an element is \(\text{Average atomic mass}=\sum_{i}( \text{fractional abundance}_i\times\text{atomic mass}_i)\). The fractional abundance of boron - 10 is \(\frac{19.78}{100}=0.1978\) and its atomic mass is \(10.01\). The fractional abundance of boron - 11 is \(\frac{80.22}{100}=0.8022\) and its atomic mass is \(11.01\).

Answer:

B

Question 22