Theory Unit 2 - Trends & Electron Configuration Flashcards
Atomic Size
Size of an atom.
Depends on the number of energy levels and the overall charge of the nucleus (the nucleus’s charge depends on the number of protons).
As you go down a group you are adding energy levels (rings around the nucleus) so the atomic size increases.
As you go across a period the atomic size decreases because the energy levels (which contain negative electrons) are increasingly attracted to the positive protons in the nucleus of the atom.
Electronegativity
Tendency of an atom to attract electrons to itself when it combines with another element.
Electronegativity increases from left to right across a period on the periodic table.
Electronegativiy decreases as you go down a group on the periodic table.
Bond Pairs
Pairs of electrons which form a bond.
Lone Pairs
Electron pairs which are not involved in bonding. They do however, affect the shape because electron pairs repel other electron pairs.
Rules for Writing Lewis Dot Structures
- Total the Valence Electrons and Update during each step.
- Form a single bond between the central atom and each surrounding atom (each bond uses two electrons).
- Place electrons around the outer atoms until you run out or they each have eight electrons around them. (Hydrogen and Helium can only have two electrons around them).
- Place any remaining electrons around the central atom.
- Does each atom other than hydrogen have eight electrons around it?
- Rearrange (share) electrons so that all atoms other than hydrogen have eight electrons around them.
Octet Rule
All atoms other than hydrogen and helium bond to fill their valence shell with eight electrons.
Duet Rule
Hydrogen bonds to fill it’s valence shell with two electrons. Helium already has two electrons and thus does not need to form bonds to increase stability.
Violations of the Octet Rule
Be - 4
B - 6
P - 8 or 10
S - 8, 10, or 12
Xe - 8, 10, or 12
VSPER
Valence Shell Electron Pair Repulsion
Most important aspect of determining the shape or geometry of a molecule. The molecule will adopt the shape which minimizes te electron pair repulsion.
Which of the following elements has the largest atomic radius?
A. nitrogen B. oxygen C. fluorine D. neon
N
(least number of protons attracting the electrons on the energy levels)
Which has the largest atomic radius?
K
Na
Rb
Li
Rb
(most energy levels)
Which has the smallest atomic radius?
A. fluorine B. chlorine C. bromine D. iodine
F
(least number of energy levels)
Which has the highest electronegativity?
Na
Al
S
Cl
Cl
Which has the lowest electronegativity?
F
I
Br
Cl
I
What is the Lewis dot structure of Br₂?
What is the Lewis dot structure of XeF₄?
What is the Lewis dot structure of [NO₂]‾¹?