Course Saver General Chemistry Flashcards
What is the periodic trend for atomic radius?
Down and to the left. Towards Fr (In France you get Fat)
Why does the atomic radius get larger as you go to the left?
Effective Nuclear Charge = Zeff
- Gets larger as you go to the right, making the atomic radius smaller.
Zeff = Z - S Z = nuclear charge S = shielding electrons (core electrons/closer to the nucleus)
What is the radius of a neutral atom?
Atomic Radius
What is the radius of a charged species (ion)?
Ionic Radius
Is the ionic radius of a cation compared to its neutral species larger or smaller?
The cation is significantly smaller than its neutral species.
- metals typically form cations
Is the ionic radius of a anion compared to its neutral species larger or smaller?
The anion is significantly larger than its neutral species.
- non-metals typically form anions
Who typically forms cations?
Metals
Who typically forms anions?
Non-metals
What is an Isoelectronic Series?
When a group of atoms have the same number of electrons.
Ex: S2-, Cl-, Ar, K+, Ca2+
all isoelectronic to Ar
In an isoelectronic series, who has the smallest ionic radius?
The most positive ion, most protons.
- If they all have the same number of electrons, the one with the most protons will pull the electrons in tighter, making it smaller.
In an isoelectronic series, who has the largest ionic radius?
The more negative ion, most electrons.
What is ionization energy?
The energy required to remove an electron.
- Related to oxidation
What is the trend for Ionization Energy?
Up and to the right. Towards He.
- Opposite of Atomic Radius
Why is the ionization energy endothermic?
Removing an electron requires energy.
Why does the ionization energy increase going to the right?
The effective nuclear charge (Zeff) increases to the right. Which makes it harder to remove an electron, requiring a greater ionization energy.
Why does the ionization energy increase going up the periodic table?
The atomic radius decreases. The electrons are closer to the nucleus, making them harder to remove.
Why are the alkali metals so reactive with H2O?
Because they have such low ionization energies, so they get oxidized really easily.
What are the 2 exceptions to the ionization energy rule?
B & O have slightly lower energies (same goes for Al & S
- If Boron loses an electron then he will have a full shell.
- If Oxygen loses an electron then it will have a 1/2 full valence shell.
What is the energy change associated with gaining an electron?
Electron Affinity
- Exact opposite of Ionization Energy
- Associated with reduction
Why is Electron Affinity typically exothermic?
Gaining an electron is energetically favorable, because it lowers the atoms energy.
What is the periodic trend for Electron Affinity?
It increases as you go to the right.
- It becomes more exothermic or negative.
What are the exceptions to the Electron Affinity trend?
- Noble Gases: have a filled octet, they don’t want another electron. They have a positive electron affinity & are endothermic.
- Group 2 & 15 (Be & N columns): for the same reason as the ionization energy exception (full or 1/2 full sub-shells). They are either endothermic or only slightly exothermic.
What is the periodic trend for Electronegativity?
Up and to the right. Towards F.
What is electronegativity?
Measure of how close an atom pulls the shared electrons in a covalent bond to them.
The most polar bond between 2 atoms is the one that has the greatest …
difference in electronegativity
Ex: C-F > C-O > C-N
Most polar/ greatest diff. in electronegativity.
Which of the periodic trends is related to covalent bonding?
Electronegativity
Which of the periodic trends is related to ionic bonding?
Ionization Energy & Electron Affinity
