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Define electronegativity - Leaving Cert Chemistry - Question b - 2003

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Define electronegativity. Describe using dot and cross diagrams the bonding in the water molecule. What is the shape of the water molecule? Which of the following ... show full transcript

Worked Solution & Example Answer:Define electronegativity - Leaving Cert Chemistry - Question b - 2003

Step 1

Define electronegativity.

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Answer

Electronegativity is the relative measure of attraction or number expressing the attraction for shared electrons in a covalent bond. It indicates how strongly an atom can attract and hold onto electrons in a chemical bond.

Step 2

Describe using dot and cross diagrams the bonding in the water molecule.

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Answer

The water molecule, H₂O, consists of two hydrogen atoms and one oxygen atom. In dot and cross diagrams, the oxygen atom has six electrons in its outer shell, while each hydrogen atom has one electron.

The bonding can be illustrated as follows:

  .   .
   O
  / \
 H   H

In this diagram, the dots represent the electrons from the oxygen atom, and the crosses represent the electrons from the hydrogen atoms, indicating the sharing of electrons.

Step 3

What is the shape of the water molecule?

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Answer

The shape of the water molecule is V-shaped or bent.

Step 4

Which of the following angles, 104°, 107°, 109°, 120° or 180° would you expect to be closest to the bond angle in the water molecule? Explain your answer.

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Answer

I would expect the bond angle in the water molecule to be closest to 104°. This is due to greater repulsion by lone pairs of electrons. The two lone pairs on the oxygen exert repulsion, pushing the bonds between the hydrogen atoms closer together, which reduces the bond angle from the ideal tetrahedral angle (109.5°) to approximately 104°.

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