8.1.5 Periodic Relationships

Question 1

Periodic Relationships

Answer 1

• The periodic table is arranged with columns of elements having similar valence electron configurations.
• Noble gas electron configurations are very stable.
• Groups on the periodic table tend to react to gain or lose electrons to match a noble gas electron configuration.

Question 2

note

Answer 2

• Valence electrons are electrons in orbitals beyond the
  previous noble gas core. These electrons determine the
  bonding characteristics of an element.
• The periodic table is arranged with columns of elements having similar valence electron configurations. The columns are referred to as groups.
• For example, the alkali metals (group 1) all have one valence electron in an s orbital.
• Noble gas electron configurations are very stable.
• This stability is because any electrons added to a noble gas have to go into the next highest energy level. For example, the next available orbital after the neon electron configuration (1s 2 2s 2 2p 6 ) is the 3s orbital. However, since every electron is paired, a relatively large amount of energy must be put in to remove an electron.

Question 3

note 2

Answer 3

• Due to electron shielding, the energies of the 4f orbitals, the 6s orbital, and the 5d orbitals are all approximately equal. Likewise, the energies of the 5f orbitals, the 7s orbital, and the 6d orbitals are all approximately equal. Because of this equivalence, the order in which orbitals fill is not immediately
  obvious.
• However, the periodic table is arranged in such a way that the order that orbitals fill is reasonably clear. The
  lanthanide series can be thought of as occupying the space on the periodic table between the elements filling the 6s orbital and the elements filling the 5d orbitals. Therefore, the 4f orbitals generally fill after the 6s orbital and before the 5d orbitals. Likewise, the actinide series can be thought of as occupying the space on the periodic table between the elements filling the 7s orbital and the elements filling the 6d orbitals. Therefore, the 5f orbitals generally fill after the 7s orbital and before the 6d orbitals.
• However, there are exceptions to the rule. For example, the electron configuration of thorium (Th) is [Rn]6d 2 7s 2 , while the electron configuration of protactinium (Pa) is [Rn]5f 2 6d 1 7s 2 .
• Groups on the periodic table tend to react to gain or lose electrons to match a noble gas electron configuration.
• Alkali metals (group 1) such as potassium have one more valence electron than the previous noble gas core. Therefore, alkali metals tend to react to lose one electron, forming a +1 oxidation state which is isoelectronic with the previous noble gas.
• Alkaline earth metals (group 2) such as calcium have two more valence electrons than the previous noble gas core. Therefore, alkaline earth metals tend to react to lose two electrons.
• Halogens (group 17) such as chlorine have one less valence electron than the next noble gas core. Therefore, halogens tend to react to gain one electron.
• Chalcogens (group 16) such as oxygen have two less valence electrons than the next noble gas core. Therefore, chalcogens tend to react to gain two electrons.

Question 4

Tellurium is located in which block on the periodic table?

Answer 4

p block

Question 5

Which species in the following series is not isoelectronic with others?

Cl −, Ca2+, Ar, K, P3−

Answer 5

K

Question 6

Which of the following characteristics is most alike in elements that have similar chemical properties?

Answer 6

Valence electron configuration

Question 7

Which group does selenium belong to?

Answer 7

chalcogens

Question 8

Elements with partially-filled 4f orbitals are part of which of the following?

Answer 8

The lanthanide series

Question 9

What is the most common oxidation state for alkaline earth metals?

Answer 9

+2

Question 10

How many electrons must chalcogens gain / lose to achieve a noble gas configuration?

Answer 10

gain two

Question 11

What family does rubidium belong to?

Answer 11

alkali metals

Question 12

What is the general order of filling of the 4f, 5d, and 6s orbitals?

Answer 12

6s, 4f, 5d

Question 13

Which of the following best defines isoelectronic?

Answer 13

having the same number of electrons