A) Explain which of the above are isotopes of Neon. b) A student states "If two atoms have different numbers of neutrons, they must be different elements". Is this statement true or false? Explain you

Isotopes are atoms of the same element that have the same number of protons (atomic number, Z) but different numbers of neutrons, resulting in different mass numbers (A).

The atomic number (Z) is the subscript, and the mass number (A) is the superscript.

• (A) $^{20}_{10}\text{Ne}$: Atomic number = 10, Mass number = 20
• (B) $^{21}_{10}\text{Ne}$: Atomic number = 10, Mass number = 21
• (C) $^{22}_{10}\text{Ne}$: Atomic number = 10, Mass number = 22
• (D) $^{23}_{10}\text{Ne}$: Atomic number = 10, Mass number = 23

All four species (A, B, C, D) have an atomic number of 10, which means they all have 10 protons and are therefore all atoms of Neon. They have different mass numbers (20, 21, 22, 23), indicating different numbers of neutrons.

• Therefore, all of the given species ($^{20}_{10}\text{Ne}$, $^{21}_{10}\text{Ne}$, $^{22}_{10}\text{Ne}$, and $^{23}_{10}\text{Ne}$) are isotopes of Neon.

2) A student states "If two atoms have different numbers of neutrons, they must be different elements". Is this statement true or false? Explain your answer using a suitable example.

The statement claims that a difference in neutron count must mean different elements. This is incorrect because isotopes of the same element have different numbers of neutrons. The identity of an element is determined by its number of protons (atomic number), not its number of neutrons.

Consider the element Carbon (C), which always has 6 protons.

• Carbon-12 ($^{12}_6\text{C}$) has $12 - 6 = 6$ neutrons.
• Carbon-14 ($^{14}_6\text{C}$) has $14 - 6 = 8$ neutrons.

Carbon-12 and Carbon-14 have different numbers of neutrons (6 vs. 8), but they are both the same element, Carbon. This demonstrates that the student's statement is false.

3) Determine the percentage abundance of the two isotopes of lithium-7 and lithium-6, given that the Relative Atomic Mass of the element is 6.941.

Let $x$ be the fractional abundance of Lithium-7 ($^{7}\text{Li}$).
Then, the fractional abundance of Lithium-6 ($^{6}\text{Li}$) will be $(1-x)$.

The relative atomic mass is the weighted average of the masses of its isotopes.

Using the mass numbers as approximate isotope masses:

Percentage abundance of Lithium-7:

Percentage abundance of Lithium-6:

The percentage abundance of Lithium-7 is \boxed{\text{94.1%}} and Lithium-6 is \boxed{\text{5.9%}}.

4) Determine Group and Period of Boron of atomic no 5 using S & P notation.

Boron has 5 electrons. Following the Aufbau principle:

The period number corresponds to the highest principal quantum number ($n$) in the electron configuration. In this case, the highest $n$ is 2.

• Period: 2

For main group elements (s-block and p-block), the group number is determined by the number of valence electrons. Valence electrons are those in the outermost shell (highest $n$).
The outermost shell is $n=2$, which contains $2s^2 2p^1$.
Number of valence electrons = $2 (\text{from } 2s) + 1 (\text{from } 2p) = 3$.
For p-block elements, the modern IUPAC group number is $10 + \text{number of valence electrons}$.

• Group: $10 + 3 = \textbf{13}$

The Group of Boron is $\boxed{\text{13}}$ and the Period is $\boxed{\text{2}}$.