Simple Molecular substances

What are simple molecular substances?

Made up of molecules containing a few atoms joined together by covalent bonds

What are some common examples of simple molecular substances?

Hydrogen, chlorine, oxygen, nitrogen, methane, water, hydrogen chloride

Hydrogen, H2

Hydrogen atoms have just one electron. They only need one more to complete the first shell so they often form single covalent bonds, either with other hydrogen atoms or with other elements to achieve this

Chlorine, Cl2

Each chlorine atom needs just one more electron to complete the outer shell so two chlorine atoms can share one pair of electrons and form a single covalent bond.

Oxygen, O2

Each oxygen atoms needs two more electrons to complete it's outer shell so in oxygen gas two atoms share two pairs of electrons with each other making a double covalent bond.

Nitrogen, N2

Nitrogen atoms need three more electrons so two nitrogen atoms share three pairs of electrons to fill their outer shells. This creates a triple bond.

Methane, CH4

Carbon has four outer electrons, which is half a full shell. It can form four covalent bonds with hydrogen atoms to fill up its outer shell.

Water, H2O

In water molecules, the oxygen shares a pair of electrons with two H atoms to form two single covalent.

Hydrogen Chloride, HCl

This is similar to H2 and Cl2. Again, both atoms only need one more electron to complete their outer shell.

What type of structures do substances containing covalent bonds usually have?

Simple molecular structures

What are some examples of simple molecular substances?

H2, HCl, H2O, CH4

What holds the atoms within simple molecular substances together?

Very strong covalent bonds

What type of forces exist between molecules in simple molecular substances?

Very weak intermolecular forces

What are the melting and boiling points of simple molecular substances like?

Very low

Why do simple molecular substances have low melting and boiling points?

Weak intermolecular forces are easy to overcome

What is the physical state of simple molecular substances at room temperature?

Gases or liquids

How does the size of molecules affect the strength of intermolecular forces?

As molecules get bigger, the strength of intermolecular forces increases

What happens to the melting and boiling points as the size of molecules increases?

They increase

Do simple molecular substances conduct electricity?

No, because they aren't charged and have no free electrons or ions