Atomic Theory Flashcards
Atomic Theory
All matter is made of atoms- Atoms are indivisible and indestructible
AToms of a specific element are identical in mass and properties
Compounds are formed by whole number ratios
Chemical reactions are rearrangements of atoms
Orbitals
Regions of space around nucleus where electrons reisde
Heusenberg’s Uncertainty Principle
Impossible to determine both the momentum or location of an electron
Can determine one or the other
n
Principle quantum number
Overall energy of orital
Max number of electrons that a shell can hold
2n^2
l
Azimuthal quantum number
l= 0 to (n-1)
Orbital shape 0=s 1=p 2=d 3=f
m(l)
Magnetic quantum number
Orientation of orbitals in space
= -l to +l
m(s)
Spin number
+/- 1/2
Pauli Exclusion Principle
No 2 electrons in an atom can have the same set of quantum numbers
Aufbau Principle
Lower subshells filled before higher subshell
Characteristics of Covalent Bonds
Bond length
Bond energy
Polarity
Characteristics of Covalent Bonds- Bond Length
decreases as number of shared electrons increases
Characteristics of Covalent Bonds- Bond energy
Energy required to break the bond
Increases as number of shared electrons increases
Characteristics of Covalent Bonds-Polarity
Formation of partially charged regions
Ionic Bonds
Comlete transfer of electrons across atoms
Held together by electrostatic forces
London Dispersion forces
Weakest
Electron density between atoms changes briefly, forming a temporary dipole
Can induce dipoes in neighbouring molecules
In NP compounds
Dipole-Dipole
Polar solids and liquids (not gases)
Rearrangement of atoms so that partially positive regions are close to partially negative regions
H bonds
Fairly strong
H attracted to O,N.F
Bonding Orbitals
Signs of atomic orbitals are the same
Electrons spend most of time between nuclei of 2 atoms (more stable)
Anti-bonding orbitals
Signs of atomic orbitals are different
Electrons spend most of time outside of nuclei of 2 atoms (not as stable)
Sigma bond
Head to head overlap of orbitals
Pi bond
Parallel overlap of orbitals
Can’t rotate
Factors Affecting Bond Strength
Bond order
Atomic Radii
Polarity
Lone Pairs
Factors Affecting Bond Strength- Bond Order
of bonds
single bond= 1…etc
Higher bond order= lower bond length….. INCREASES bond strength
Factors Affecting Bond Strength- Atomic Radii
Increase radius= increased bond length….DECREASES BOND STRENGTH
Factors Affecting Bond Strength- Polarity
Increase polarity= INCREASED bond strength
Factors Affecting Bond Strength- Lone Paris
Increased LP= DECREASED bond strength
Repulsion between LP weakens bond
Hund’s Rule
Electrons must fill up orbitals of the same or different energy levels before pairing up
