A sample of sulfur from a volcano was analyzed to give the following composition of isotopes (Atomic No. of S = 16):

(a) Define the term isotope.

An isotope refers to atoms of the same element that have the same number of protons but different numbers of neutrons. This leads to different mass numbers for the isotopes of an element. While isotopes of an element have nearly identical chemical properties, their physical properties, like mass, may differ.

(b) Define the term relative atomic mass.

The relative atomic mass (also known as atomic weight) is the weighted average mass of an element’s naturally occurring isotopes, taking into account their relative abundances. This value is measured relative to the mass of carbon-12, which is assigned a value of exactly 12.

(c) Calculate the relative atomic mass of sulfur.

To calculate the relative atomic mass of sulfur, we need the masses and abundances of the isotopes of sulfur. Sulfur has two main isotopes: sulfur-32 (S-32) and sulfur-34 (S-34). For example, assume sulfur-32 has an abundance of 95% and sulfur-34 has an abundance of 5%. The calculation would be:

Relative Atomic Mass=(32×0.95)+(34×0.05)\text{Relative Atomic Mass} = (32 \times 0.95) + (34 \times 0.05) Relative Atomic Mass=30.4+1.7=32.1\text{Relative Atomic Mass} = 30.4 + 1.7 = 32.1

This means the average relative atomic mass of sulfur is approximately 32.1.

(d) Complete the following table:

Isotope Mass Number Abundance
S-32 32 95%
S-34 34 5%

(e) Where will you place sulfur in the periodic table?

Sulfur is placed in Group 16 (the Chalcogens) and Period 3 of the periodic table. Elements in Group 16 are typically non-metals, and sulfur is no exception.

(f) How many electrons will sulfur lose or gain to acquire a stable configuration?

Sulfur has 6 valence electrons and needs 2 more electrons to complete its octet. Therefore, sulfur will gain 2 electrons to form an anion (S²⁻) and acquire a stable configuration.

(g) How many atoms of sulfur are there in 0.3 moles of sulfur?

The number of atoms in a given number of moles can be calculated using Avogadro’s number (6.022 × 10²³ atoms/mole). So, in 0.3 moles of sulfur, the number of atoms is:

Number of atoms=0.3×6.022×1023=1.8066×1023 atoms\text{Number of atoms} = 0.3 \times 6.022 \times 10^{23} = 1.8066 \times 10^{23} \, \text{atoms}

Thus, there are approximately 1.81 × 10²³ atoms of sulfur in 0.3 moles.

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