S1 Exam - Unit 7

Front

What is the Lewis structure for water (H2O)?

Back

The Lewis structure for water shows the oxygen atom in the center with two hydrogen atoms bonded to it, and two unshared pairs of electrons on the oxygen.

Front

How many unshared pairs of electrons does oxygen have in water?

Back

Oxygen has 2 unshared pairs of electrons in the Lewis structure of water.

Front

What is a cation?

Back

A cation is a positively charged ion.

Front

What is the correct structure for ammonia (NH3)?

Back

The correct structure for ammonia has a nitrogen atom bonded to three hydrogen atoms with one unshared pair of electrons on nitrogen.

Front

What is the Lewis structure for formaldehyde (CH2O)?

Back

The Lewis structure for CH2O shows a carbon atom double bonded to an oxygen atom and single bonded to two hydrogen atoms.

Front

How many valence electrons does sulfur (S) have?

Back

Sulfur has 6 valence electrons.

Front

What happens to sulfur's valence electrons when it forms an ionic bond?

Back

Sulfur will gain 2 valence electrons when forming an ionic bond.

Front

What is the significance of unshared pairs of electrons in a molecule?

Back

Unshared pairs of electrons, or lone pairs, can affect the shape and reactivity of a molecule.

Front

What is the difference between a cation and an anion?

Back

A cation is a positively charged ion, while an anion is a negatively charged ion.

Front

How do you determine the number of valence electrons in an element?

Back

The number of valence electrons can be determined by the group number of the element in the periodic table.