Lose, gain or share

The idea

An element with fewer than four valence electrons generally tends to lose electrons, and one with more than four tends to gain electrons, to complete its octet.

Closer to which side?

An atom with an incomplete outer shell can reach an octet by losing, gaining or sharing electrons.

An atom has just 1 valence electron. Which way does such an atom tend to reach an octet?

• Lose that 1 electron
• Gain 7 electrons
• Gain 1 electron

Slide the valence electrons

Change the number of valence electrons. Solid orange dots are electrons. Dashed circles are empty places up to eight.

A simple guide

If an atom has fewer than four valence electrons, it generally tends to lose them. If it has more than four, it tends to gain electrons. Either way, it ends with an octet.

An element with fewer than four valence electrons generally tends to lose electrons, and one with more than four tends to gain electrons, to complete its octet.

Notes

Fewer than four valence electrons: the atom tends to lose electrons. More than four: it tends to gain electrons, to complete its octet.

Check yourself

An atom has 2 valence electrons. What does it tend to do?

An atom has 6 valence electrons. What does it tend to do?

An atom has 7 valence electrons. How many electrons must it gain to complete its octet?

Answer: 1

8 − 7 = 1.

Which atom is more likely to lose electrons?

• Lose electrons — correct. Yes!
• Gain electrons. An atom with fewer than four valence electrons tends to lose electrons.
• Gain 6 electrons at once. Such an atom tends to lose its 2 electrons, not to gain 6.
• Lose electrons. An atom with more than four valence electrons tends to gain electrons.
• Gain electrons — correct. Yes!
• Lose all 6 electrons. Such an atom tends to gain 2 electrons, not to lose 6.
• One with 7 valence electrons. An atom with more than four valence electrons tends to gain electrons.
• One with a complete octet. An atom with a complete octet is largely unreactive.
• One with 1 valence electron — correct. Yes!