Three steps to a covalent compound
Working out the bonding.
Why two hydrogens for one oxygen?
Hydrogen needs only one electron, but oxygen needs two. How can oxygen share its two electrons with an atom that needs only one?
What do you think happens in water?
What this lesson covers
The idea
Write each atom's electronic configuration, find how many electrons it needs to complete its octet (or duplet), and let atoms share electrons to meet those needs; atoms of different elements bonded this way form a covalent compound.
Why two hydrogens for one oxygen?
Hydrogen needs only one electron, but oxygen needs two. How can oxygen share its two electrons with an atom that needs only one?
What do you think happens in water?
- Two hydrogen atoms each share one electron with one oxygen atom
- One hydrogen atom shares two electrons with one oxygen atom
- One oxygen atom gives its two electrons to one hydrogen atom
Follow the steps
Pick a compound. Use the step buttons to go through the three steps.
The method
Write the electronic configuration of each atom. Find how many electrons each needs to complete its octet (or duplet for hydrogen). Then let the atoms share electrons to meet those needs. Atoms of different elements bonded this way form a covalent compound.
Write each atom's electronic configuration, find how many electrons it needs to complete its octet (or duplet), and let atoms share electrons to meet those needs. Atoms of different elements bonded this way form a covalent compound.
Notes
Write each atom's configuration, find the electrons it needs for an octet (or duplet), and let atoms share to meet the needs. The result is a covalent compound.
Check yourself
What is the first step in working out the bonding of a covalent compound?
An oxygen atom has 6 valence electrons. How many more does it need to complete its octet?
Answer: 2
8 − 6 = 2.
In water, hydrogen needs 1 electron and oxygen needs 2. How are the needs met?
Hydrogen chloride, HCl, is a covalent compound. Why?
- Write the name of the compound. The method starts with the electronic configuration, which shows how many valence electrons each atom has.
- Write the electronic configuration of each atom — correct. Yes!
- Find the mass of the compound. The mass is not needed to work out the bonding.
- One hydrogen atom shares both of oxygen's needs. Hydrogen needs only one electron, so it can share just one.
- Oxygen gives away its six valence electrons. The atoms share electrons in water. Oxygen does not give its valence electrons away.
- Two hydrogen atoms share one electron each with an oxygen atom — correct. Yes!
- Its hydrogen and chlorine atoms bond by sharing electrons — correct. Yes!
- Its atoms bond by transferring electrons. Atoms bonded by transferring electrons form an ionic compound. In HCl the atoms share one pair.
- It is made of atoms of a single element. HCl has atoms of two elements, hydrogen and chlorine.