PX262 - J2 - electronic configurations

guideline for electronic configurations

• atomic number $Z$, and $Z$ electrons
• fill up the $Z$ hydrogen-like energy states, labelled by $n,l,m_l$ and also $\uparrow$ and $\downarrow$
• for each $n$, there are $n$ sub-shells labelled by $l$
  • $l=0$ $(s)$ subshell is filled first, followed by $l=1(s)$, $l=2(d)$, and $l=3(f)$
  • each subshell labelled b $l$ can take up to $2\times (2l+1)$ electrons
• note: $3d$ and $4s$ are close in energy as are the $4d$ and $5s$ subshells
  • the same applies to $5d$ and $6s$
  • $4f$ is filled before the $6s$ subshell
• from these guidelines and quantitative calculations, a rough guideline for $Z\le 86$ using $s(l=0),p(l=1),d(l=2),f(l=3)$

electronic configurations

• ${}^5$B : $1s^{2}2s^{2}2p^1$

• ${}^{42}$Mo : $1s^{2}2s^{2}2p^{6}3s^{2}3p^{6}4s^{2}3d^{10}4p^{6}5s^{2}4d^4$

  • or [${}^{36}$Kr] $5s^{2}4d^4$ or [${}^{36}$Kr] $5s^{1}4d^5$

• ${}^{64}$Gd : [Xe] $6s^{2}5d^{1}4f^7$

• outermost, partially filled shells dominate the atoms' chemical activities

• eg: ${}^{65}$Tb : [Xe] $6s^{2}5d^{1}4f^8$ or [Xe] $6s^{2}4f^9$