Question 2.1 [2 marks]
Define the term covalent bond.
A covalent bond is a type of chemical bond that involves the sharing of electron pairs between atoms. These shared electrons allow each atom to attain the electron configuration of a noble gas, resulting in the stability of the compound.
Question 2.2 [3 marks]
Draw the Lewis diagram for CaF2.
The Lewis structure for calcium fluoride (CaF2) can be represented as follows:
F: F:
| |
Ca
In this representation:
- Calcium (Ca) has no valence electrons depicted since it gives away its two electrons to form bonds.
- Each fluorine (F) atom has three lone pairs of electrons and one bond pair, indicating they are sharing one electron with the calcium atom.
Question 2.3 [2 marks]
Which of the TWO products of this reaction would most likely be a crystalline solid at room temperature? Explain your answer.
The two products of the reaction are calcium sulfate (CaSO4) and hydrogen fluoride (HF). Among them, calcium sulfate (CaSO4) is most likely to be a crystalline solid at room temperature.
Explanation: Calcium sulfate is an ionic compound formed by the strong electrostatic attraction between calcium ions (Ca²⁺) and sulfate ions (SO4²⁻), resulting in a solid structure. In contrast, hydrogen fluoride is a polar covalent compound that exists as a gas or liquid under standard conditions.
Question 2.4 [2 marks]
Define electronegativity.
Electronegativity is a measure of the tendency of an atom to attract a bonding pair of electrons when it is chemically combined with another atom. It indicates how strongly an atom can pull electrons towards itself in a covalent bond.
Question 2.5 [2 marks]
Use electronegativity to determine the type of bond that CaF2 has.
The electronegativity values are approximately as follows:
- Calcium (Ca): 1.00
- Fluorine (F): 4.00
To determine the type of bond:
- The difference in electronegativity between Ca and F is 4.00 - 1.00 = 3.00.
Answer: Since the electronegativity difference is greater than 1.7, the bond in calcium fluoride (CaF2) is classified as ionic.
Question 2.6 [1 mark]
What is the VSEPR shape of HF?
The VSEPR shape of hydrogen fluoride (HF) is linear. This is because there are only two atoms bonded (H and F) and no lone pairs on the hydrogen atom, resulting in a straight-line structure.
1 answer