Chapter 3: Notes Flashcards
What do structural formulas show?
The way in which atoms are bonded together
What causes a chemical bond?
The attraction of electrons by two atomic nuclei. the nucleus of its own atom and another atom
What are valence electrons?
The electrons that occupy the outermost energy level
What are the places that electrons exist in called?
Orbitals
What is an orbital?
A region of space where there is a high probability of finding electrons of a particular energy
How many electrons can an orbital be occupied by?
one or two electrons
What is a bonding electron?
A single electron occupying an orbital
What is a lone pair?
Two electrons occupying a filled orbital (non-bonding)
what determines an atoms bonding capacity?
The maximum number of bonding electrons
What is bonding capacity?
The number of covalent bonds formed by an atom
What is electronagativity?
The tendancy for an atom to attract electrons to itself (from other atoms) when is is chemically combined with another element
How is electronegativity organized in the periodic table?
It increases from left to right
What are covalent bonds?
They involve atoms sharing of a pair of electrons to get a full (8 electron) outer shell
What is ionic bonding?
When electrons are transferred from metals (low electronegativity) to non-metals (high electronegativity)
What is the result of ionic bonding?
The formation of positive cations and negative anions
What is an example of an empirical chemical formula?
A regular formula CH(sub)2O
What is an example of a molecular formula?
CH3OOH The h’s are separated
What is an example of a Lewis formula?
A dot diagram
What is an example of a structural formula?
the line diagrams
What is an example of the stereochemical formulas?
The ones that show the depth
How do you draw the Lewis formula for polyatomic ions?
You add 1 extra electron for every negative charge
What does VSEPR stand for?
Valence Shell Electron Pair Repulsion
What is important for molecular shape?
The valence electrons of the central atoms
What is the molecular shape determined by?
The positions of the electron pairs when they are the maximum distance apart
How do valence electrons repel each other?
Electrostatically
What repels more strongly: Lone pairs or bond pairs?
Lone pairs!
What does 2 bond pairs and 0 lone pairs form?
Linear H - Be - H
What does 3 bond pairs and 0 lone pairs form?
AX3 Triagonal planar
H
l
B
/ \
H HWhat do 4 bond pairs and 0 lone pairs form?
AX4 Tetrahedral. 2 at level one below one on top
What do 3 bond pairs and 1 lone pair form?
AX3E tetrahedral. 1 below one above and one at level
What do 2 bond pairs and 2 lone pairs?
AX2E2 tetrahedral V shaped
What does 1 bond pair and 2 lone pairs create?
AXE3. Linear
What are polar molecules?
Molecules that have one end that is slightly negative and one end that is slightly positive
what does bond polarity depend on?
The elctronegativities of the bonded atoms
When are covalent bonds polar?
when the atoms have dfferent negativities
Which side of an atom is labelled as partially negative?
The side of the atom where the electron spends more time which is around the nucleus with higher electronegativity
When is a covalent bond non-polar?
When there is no difference in electronegativity ex H-H
When is a covalent bond slightly polar?
When the difference of electronegativity is between 0.1 - 1.0 ex H -Cl
When is a covalent bond very polar?
When the difference of electronegativity is between 1.1 - 2.0 H - F
When is a bond ionic?
When the difference in electronegativity is greater than 2.1
What is the bond dipole?
The charge separation that occurs as a result of the different electronegativities of bonded atoms
What is the bond dipole represented by?
An arrow that points from lower to higher electronegativity
What happens in non polar molecules with a bond dipole?
the bond dipoles cancel out, leaving a molecular dipole of 0 ex. CO2
Why are molecules that are symetrical non-polar?
Becuase the dipole moments balance
