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Argon (Ar) is a gaseous unreactive element that exists as single atoms - Leaving Cert Chemistry - Question 5 - 2018
Question 5
Argon (Ar) is a gaseous unreactive element that exists as single atoms. Why is this element unreactive? Fluorine and oxygen are gaseous elements that exist as the d... show full transcript
Worked Solution & Example Answer:Argon (Ar) is a gaseous unreactive element that exists as single atoms - Leaving Cert Chemistry - Question 5 - 2018
Step 1
Why is this element unreactive?
Answer
Argon (Ar) is a noble gas, found in Group 18 of the periodic table. It has a stable electron arrangement, with eight electrons in its outer shell. This full outer shell configuration makes argon unreactive, as it does not need to gain or lose electrons to achieve stability.
Step 2
Draw dot and cross diagrams to show the covalent bonding in F₂ and in O₂.
Answer
For F₂:
F •
|
•F
In this diagram, a single shared pair of electrons is shown between the two fluorine atoms.
For O₂:
O ••
|
•O ••
Here, each oxygen atom shares two pairs of electrons, depicted with two lines (one pair) connecting the atoms.
Step 3
Step 4
Use the properties given in the table to identify which substance, A, B, or C, or water, is most likely to:
Answer
(i) have ionic bonding:
- Substance C is most likely to have ionic bonding due to its high melting point (730 °C) indicating strong ionic forces.
(ii) be gaseous and have polar covalent bonding:
- Substance B, with a lower boiling point of -85 °C, is likely gaseous at room temperature and has polar covalent bonding (electronegativity difference = 0.96).
(iii) have pure covalent bonding:
- Substance A, with a very low melting point (-210 °C) and boiling point (-85 °C), likely has pure covalent bonding as it is a simple molecular substance, exhibiting weak intermolecular forces.
Each conclusion is drawn based on the boiling and melting points along with electronegativity differences.
Step 5
What is the shape of a water molecule?
Answer
The shape of a water molecule (H₂O) is described as 'v-shaped' or 'bent' due to the two hydrogen atoms being bonded to the oxygen atom at an angle of approximately 104.5 degrees. This angular shape arises from the repulsion between the lone pairs of electrons on the oxygen atom, which push the hydrogen atoms closer together.