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Covalent Bonds Formation

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Covalent Bonds Formation

Help a materials science team predict how atoms bond. Use each atom’s outer-shell electrons to explain and represent covalent bonds. For dot-and-cross diagrams, show each atom’s electrons with a different symbol.

Mission 1: Choose a molecular material

The team is testing small molecules for a new material. Each candidate contains only non-metal atoms.

1.Which statement best describes how a covalent bond forms between non-metal atoms?

The atoms share one or more pairs of electrons.
One atom transfers protons to another.
The atoms exchange their nuclei.
The atoms become oppositely charged ions.

2.Select every molecule listed that contains covalent bonds: H₂, H₂O, CO₂ and CH₄.

3.A hydrogen atom has one electron in its first shell, which is full at two. Explain why two hydrogen atoms form a single covalent bond in H₂.

Mission 2: Decode the electron evidence

Use the outer-shell electron counts to work out how many shared pairs each atom needs.

Hydrogen (H): 1 outer electron; first shell is full at 2.

Carbon (C): 4 outer electrons; outer shell is full at 8.

Nitrogen (N): 5 outer electrons; outer shell is full at 8.

Oxygen (O): 6 outer electrons; outer shell is full at 8.

4.An oxygen atom has six outer-shell electrons. How many additional shared electrons does it need for a full outer shell, and how many covalent bonds does it usually form?

5.Carbon has four outer-shell electrons. Predict the number of single covalent bonds a carbon atom usually forms to reach an outer shell of eight electrons.

One
Two
Three
Four

6.Draw a dot-and-cross Lewis structure for water, H₂O. Show two O–H shared pairs and oxygen’s remaining lone pairs.

Draw and label the Lewis structure here.

7.Draw a dot-and-cross Lewis structure for ammonia, NH₃. Show three N–H shared pairs and nitrogen’s remaining lone pair.

Draw and label the Lewis structure here.

Mission 3: Check your model

A useful bonding model explains both the shared electrons and the properties of substances.

8.A student says, “The electrons in a covalent bond belong only to one atom.” Correct this statement using the idea of a shared pair.

9.Compare a typical simple molecular covalent substance with an ionic compound. State how electrons behave in each and compare their usual melting points.

10.Oxygen and hydrogen do not attract shared electrons equally. What type of covalent bond does this produce in an O–H bond: polar or non-polar? Explain briefly.