Climbing the energy ladder

The idea

The K shell (n = 1) is closest to the nucleus and has the least energy; the farther a shell is from the nucleus, the higher its energy.

Near or far

Think of an electron in each shell. Some shells are close to the nucleus and some are far.

Which shell do you think holds an electron of the least energy?

• The shell closest to the nucleus
• The shell farthest from the nucleus
• All shells give the same energy

Choose a shell

Pick a shell for the electron. The ladder on the right shows its energy level (the heights are only to show the order).

Farther means more energy

The K shell is closest to the nucleus and has the least energy. As we move outward, each shell has more energy than the one before it.

The K shell (n = 1) is closest to the nucleus and has the least energy. The farther a shell is from the nucleus, the higher its energy.

Notes

The K shell (n = 1) is closest to the nucleus and has the least energy. The farther a shell is from the nucleus, the higher its energy.

Check yourself

Which shell has the least energy?

Which statement is correct?

As we move away from the nucleus, the energy of the shells …

• N shell. The N shell is farther from the nucleus than K, so its energy is higher.
• L shell. The L shell has more energy than the K shell.
• K shell — correct. Yes!
• An electron in the L shell has more energy than one in the K shell — correct. Yes!
• An electron in the K shell has more energy than one in the L shell. The K shell is closest to the nucleus and has the least energy.
• The K shell and the L shell have the same energy. The L shell (n = 2) has more energy than the K shell (n = 1).
• decreases. The farther a shell is from the nucleus, the higher its energy.
• increases — correct. Yes!
• stays the same. Each shell has a definite energy, and the energy is higher in the shells farther out.