Why atoms join
Lower energy and the chemical bond.
Rolling downhill
A ball rolls downhill because it ends up lower and more stable. Atoms may do something similar when they join.
When atoms combine, how do you think the energy of the joined atoms compares with the energy of the separate atoms?
What this lesson covers
The idea
When atoms combine, the total energy of the system becomes lower than the sum of the energies of the separate atoms, making it more stable; the force that holds atoms together is a chemical bond.
Rolling downhill
A ball rolls downhill because it ends up lower and more stable. Atoms may do something similar when they join.
When atoms combine, how do you think the energy of the joined atoms compares with the energy of the separate atoms?
- Lower
- Higher
- Exactly the same
Separate or bonded?
Choose a state and look at the energy bar.
A lower-energy, more stable arrangement
When atoms combine, the arrangement has lower energy than the atoms had apart, so it is more stable. The force that holds the atoms together is the chemical bond.
When atoms combine, the total energy of the system becomes lower than the sum of the energies of the separate atoms, making it more stable. The force that holds atoms together is a chemical bond.
Notes
Combined atoms have lower total energy than the separate atoms, so they are more stable. The force that holds them is a chemical bond.
Check yourself
What is the force that holds atoms together called?
How does the energy of two atoms joined together compare with the sum of the energies of the separate atoms?
What does the lower energy do for the combined atoms?
- An octet. An octet is the set of 8 electrons in a stable valence shell. It is not the force that holds atoms together, which is called a chemical bond.
- A chemical bond — correct. Yes!
- An electron shell. An electron shell is a region around the nucleus where electrons are found, not the force that holds atoms together.
- It is higher. When atoms combine, the total energy of the system becomes lower.
- It is exactly the same. The energy of the combined system is lower than the sum of the energies of the individual atoms.
- It is lower — correct. Yes!
- It makes the arrangement more stable — correct. Yes!
- It makes the atoms break apart. A lower energy makes the arrangement more stable, not less.
- It makes the atoms lose all their electrons. The atoms stay joined as a stable arrangement; they do not lose all their electrons.