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5. (a) Argon (Ar) is a gaseous unreactive element that exists as single atoms - Leaving Cert Chemistry - Question 5 - 2018
Question 5
5. (a) Argon (Ar) is a gaseous unreactive element that exists as single atoms. Why is this element unreactive? (5) (b) Fluorine and oxygen are gaseous elements th... show full transcript
Worked Solution & Example Answer:5. (a) 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 unreactive primarily because it has eight electrons in its outer shell, giving it a stable electron arrangement. It is classified as a noble gas, which means it has a full outer shell and does not readily engage in chemical reactions, allowing it to remain inert.
Step 2
Draw dot and cross diagrams to show the covalent bonding in F2 and in O2.
Answer
For the molecular structure of fluorine (F2), we have:
X: F ⋅
X: F ⋅
Draw two dots to represent the shared pair of electrons. In addition, there are incorrect lone pairs for a complete representation.
For oxygen (O2):
: O:
: O:
In this diagram, each oxygen shares two pairs of electrons, with no need to show lone pairs explicitly.
Step 3
Step 4
Use the properties given in the table to identify which substance, A, B or C, is most likely:
Answer
(i) Ionic bonding: The substance most likely to have ionic bonding is A, as it has a low melting and boiling point, indicating weaker intermolecular forces instead of covalent bonding.
(ii) Gaseous and have polar covalent bonding: Substance B is likely gaseous at room temperature due to its low melting and boiling points, and it exhibits polar covalent bonding due to the electronegativity difference of 0.96.
(iii) Pure covalent bonding: Substance A is identified as having pure covalent bonding because of a negligible electronegativity difference (0) between its constituent atoms.
This reasoning emphasizes how each substance's properties relate to its bonding characteristics.
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'. This geometry arises due to the two hydrogen atoms bonded to the oxygen atom, along with the repulsion between the lone pairs of electrons on the oxygen, creating an angle of approximately 104.5°.