3- exceptions for electron configurations Flashcards
Anion rules
Anion Rules
Add the extra electrons corresponding to the ion charge to the total number of electrons in the neutral atom before proceeding to write the configuration
Cation Rules
Cation Rules
Write the configuration for the neutral atom first
Remove the electrons from the orbital from the highest period number, n, as these represent the electrons in the valence shell
remove electrons from the highest period number (as these electrons are the furthest away)
Explaining Charges
Recognizing atoms in their excited states
Excited state –> electrons have gained energy and moved into a higher orbital, the total number of electrons in the atom have not changed
Count the number of electrons to determine the atom
The electron configurations below represent atoms in their excited states. Identify each atom and write its ground state electron configuration.
compare ground state (normal configuration) to excited state
Exceptions for writing electron configurations d-orbitals
Half filled and fully filled d-orbitals are more stable
know these exceptions!
Key Ideas of Lewis theory of bonding are:
Atoms and ions are stable if they have a noble gas like electron structure i.e., a stable octet of electrons
Electrons are most stable when they are paired
how can we achieve a stable octect?
Atoms form chemical bonds to achieve a stable octet of electrons in two (2) ways:
1) exchanging electrons between metal and non-metal atoms (ionic bonding) OR
2) sharing electrons between non-metal atoms (covalent bonding)
rules for drawing lewis dot diagrams –> Which atoms go to the middle and which atoms surround the central atom?
Rule 1: The central atom is usually the least electronegative atom
Rule 2: Other atoms surround the least electronegative atom
What must you do after placing the atoms in your diagram?
Rule 3: Count the total number of valence electrons, including charges
-1 ionic charge = gained 1 electron = +1 electron
+2 ionic charge = lost 2 electrons = -2 electrons
how to distribute electrons after counting for our diagram?
Rule 4: Place electron pairs between each atom to represent a single bond, then distribute the remainder of the electrons around the surrounding atoms to satisfy octet rule. [Any remaining electrons that have not been distributed can be placed on the central atom as lone pairs]
[Should an octet not be satisfied on central atom, non-bonding electrons on the outer atoms can be used to create a double bond]
How to finish a lewis dot diagram drawing?
Rule 5: Replace electrons with lines to represent bonds and place square brackets around the final structure. Indicate the charge on the structure by placing the charge on the outside of the right square bracket.
resonance structures
When more than one Lewis structure can be drawn, the molecule or ion is said to have resonance / resonance structures (ie. the double/triple bond can move in the complex)
Formal Charge (FC)
V = total number of valence electrons
N = number of non-bonding electrons
B = number of bonds
Single bond = 1
Double bond = 2
Triple bond = 3
why do we use formal charge?
A molecule will not allow for both positive and negative formal charges to exist within its structure. To adjust, electron pairs are moved from the negative atoms to form bonds
