What two blocks will always be the highest occupied level?
Valence Electrons
• Valence electrons are in the highest
energy levels. In other words, they are
farthest from the nucleus.
• The highest energy levels will always
coincide with the S- and P-orbitals.
• Therefore, the number of valence
electrons can vary from 0 to 8.
Ions
• Determine whether the number of
valence electrons are closer to 0 or 8.
• If closer to 0, atoms will lose
electrons, resulting in a cation.
• If closer to 8, atoms will gain
electrons, resulting in an anion.
• Ex. selenium (Se)
Ions
• Selenium, with 6 valence electrons, is
closer to 8 than 0.
• Selenium will gain 2 electrons to attain
the same electron configuration as the
closest noble gas, krypton.
• By gaining 2 electrons, selenium will
become an anion with a -2 charge (Se-2).
What ions will these form?
• B is
1s2
2s2
2p1
– 2 is the outermost
energy level
– it contains 3 valence
electrons, 2 in the 2s
and 1 in the 2p
Br is [Ar] 4s2 3d10 4p5
– 4 is the outermost energy
level
– it contains 7 valence
electrons, 2 in the 4s and
5 in the 4p
Exit Ticket
• How many p, n, and e do most
neutral atoms of aluminum
(Al) have?
• What’s the electron
configuration (short-cut is
fine)?
• What’s the highest energy
level?
• How many valence electrons
are there?
• What ion will Al form?
13p, 14n, 13e
[Ne]3s23p1
3
3
+3