En anglais

When sharing electrons is unfair

Science · Matter & Materials · ages 15-16

Name ______________________ Date ____________

Which element pulls shared electrons hardest of all?
- Carbon
- Oxygen
- Fluorine
In H-Cl, chlorine pulls harder than hydrogen. Which end is delta minus?
- The hydrogen end
- The chlorine end
- Both ends equally
Two identical atoms share a pair equally, as in H-H. What kind of bond is this?
- Ionic
- Nonpolar covalent
- Polar covalent
Why is carbon dioxide nonpolar overall?
- Its two equal pulls point in opposite ways and cancel
- Its bonds are nonpolar
- It has only one bond
Sodium chloride consists of Na+ and Cl- ions. What holds these ions together?
- A nonpolar covalent bond
- A polar covalent bond
- Ionic attraction
Water is a bent molecule, so its bond pulls add up and the whole molecule is polar.
Circle one: True False
H-F has a large electronegativity difference, but its electrons remain shared unequally. What type is the bond?
- Polar covalent, still shared
- Ionic, the electron moved over
- Nonpolar, the pair sits in the middle
A linear molecule has two opposite bond dipoles, but one is stronger. A student says they cancel because the molecule is straight. Which correction explains the result?
- Unequal opposite dipoles leave a nonzero overall dipole
- Any pair of opposite dipoles cancels, whatever its strength
- A linear molecule cannot have any polar bonds within it

Answer key

For grown-ups. Fold this page away before handing over the rest.

Fluorine · Electronegativity generally increases up a group and to the right across a period. Fluorine has the highest value.
The chlorine end · The stronger puller turns slightly negative, so chlorine is delta minus.
Nonpolar covalent · With a zero electronegativity difference, the bond is nonpolar.
Its two equal pulls point in opposite ways and cancel · The straight shape makes the two pulls point in opposite directions, so they cancel.
Ionic attraction · Na+ and Cl- have opposite charges. Their electrical attraction is ionic bonding.
True · The bent shape aims the pulls at an angle, so they combine.
Polar covalent, still shared · The electrons remain shared, so the bond is covalent. Unequal sharing makes it polar, despite the large electronegativity difference.
Unequal opposite dipoles leave a nonzero overall dipole · Opposite dipoles cancel only when their strengths are equal. Here the stronger dipole leaves a nonzero total, so the molecule is polar.