Module 2: Molecules Flashcards
(46 cards)
How does one distinguish an ionic compound from a molecular compound at first glance?
A metal and nonmetal (groups I or II with group VII) is usually ionic, whereas two nonmetals is usually covalent.
What are the two prime reasons for atoms to form chemical bonds?
Quantum mechanical reasons and electrostatic reasons
Most poly atomic ions are what?
Charged molecules
The phrase molecule is reserved for what kind of bonds?
Covalent: if mostly ionic, it’s called an ionic compound istead
Why do the group I metals and group VII halogens ionically bond so easily?
The Group I elements have a low enough ionization energy and Group VII elements have a high enough electron affinity to make up for the reaction
What are two characteristics usually used to characterize bonds?
Bond distance and bond energy
In general, the shorter the bond distance…?
The more stable the bond
In general, the larger the bond energy…?
The stronger and more durable the bond.
To break a bond, the ??? has to be inserted into the bond.
The same amount of bond energy
Why does bond length increase from LiCl to KCl?
Because cation size increases, lengthening the bond
Smaller bond length is associated with how much energy?
Higher bond energy
The smaller bond length-high bond energy correlation is found in what kinds of bonds?
Both ionic and covalent
Do crystalline ionic compounds conduct energy as solids or as liquids?
As liquids
Lattice energy
The reaction of ions in the gas phase that form the ionic compound
Why is it electrostatically favorable to share the electron between two hydrogen atoms?
Each proton can see the negative electron instead of the farther positive proton: energetically favorable
Why is the chemical bond between two hydrogen atoms energetically favorable from a quantum mechanics standpoint?
The more space a particle has, the lower the energy: more energetically favorable state
What does it mean that quantum systems can have their cake and eat it too?
When given two choices, quantum mechanics can choose both! Ex: sharing the electron between the two hydrogen atoms
Resonance structure
A structure that is a combination of the two possible extreme structures
Formal charge
A hypothetical charge that assumes the atom is completely covalent
How does one calculate the formal charge?
Take the total number of valence electrons for the neutral atom and subtract all valence electrons in the Lewis diagram (lone pairs plus half the shared bonds)
How does one calculate the total charge of the molecule?
The sum of the formal charges
Across a period from left to right, what happens to electronegativity?
Increases
Down a group from top to bottom, what happens to electronegativity?
Decreases
Which are more electronegative, metals or nonmetals?
Nonmetals
