Chapter 1 Flashcards
Mass number
Sum of protons and neutrons in a nucleus
How do you find the number of electrons?
Electrons equal the number of protons when the atom is neutral and vary when the atom is positively or negatively charged
How do you find the number of protons ?
Equal to the atomic number
How do you find the number of neutrons ?
Atomic mass - atomic number = number of neutrons
Which subatomic particle is most important for determining isotopes ?
Neutrons
Varying number of neutrons allow for different masses of an atom to exist even though the atomic number stays the same
Atomic mass
Sum of the mass of protons and neutrons in a given atom
Atomic weight
Weighted average of naturally occurring isotopes of an element
What was Planck’s first quantum theory ?
Energy emitted as electromagnetic radiation from matter comes in discrete bundles called quanta
Planck’s relation formula
E=hf
H is Planck’s constant = 6.626x10^-34 js
F is the frequency of radiation
E is the energy emitted
Formula for angular momentum of an electron orbiting a hydrogen nucleus
L= nh/2pi
N is the principal quantum number, positive integer
H is Planck’s constant
Energy of electron equation
E = -Rh/n^2
Rh= 2.18x10^-18 J/ electron
The energy of electron increases as the electron gets farther from the nucleus because the energy becomes LESS NEGATIVE
Ground state
Elections are in lowest orbital
Excited state
At least one electrons moved to a sub shell
Electromagnetic energy of photons can be determined by
E= hc/ lambda=-Rh[1/ni^2-1/nf^2]
C - speed of light in vacuum ( 3.0x10^8m/s)
Lambda is the wavelength of radiation
This is the energy emitted by the photon as an electron returns from the excited state back to its ground state
Lyman series
Hydrogen emission lines starting from n =1
Balmar series
H emission lines starting from n =2
Paschen series
H emission lines starting from n=3
What happens as en electron goes from higher energy level to a lower one ?
AHED
A-absorbs light
H- higher energy
E- excited
D- distant from nucleus
What does a positive E correspond to ? Negative E ?
\+E = emission -E = absorption
Heisenberg uncertainty principle
It is impossible to determine the exact location of electron
Pauli’s exclusion principle
No two electrons can have the same 4 quantum numbers
N - first principle quantum number
Any positive integer value
Higher value of n denotes higher energy level
Maximum number of electrons within a shell is 2n^2
Difference in energy between two shells decreases as the distance increases
L - angular momentum
Refers to shape and number of subshells
N-1 limits the number of subshells
S,p,d,f
Maximum number of subshells is 4l+2
Magnetic quantum number (ml)
S-l is 1
P-l is 0,-1,1
D-l is 0,-1,1,-2,2
F-l is 0,-1,-2,-3,1,2,3
Ms - spin quantum number
An object spinning about its axis
+ 1/2-
-1/2
Paired spins
When two electrons in the same orbitals have opposite spins
Parallel spins
Electrons in different orbitals with the same ms value have parallel spins
Building up principle (aufbau principle )
Electrons fill from lower to higher energy
What is the order of electron configuration ?
1s 2s 2p 3s 3p 3d 4s 4p 4d 4f 5s 5p 5d 5f 6s 6p 6d 7s 7p
How do you wrote the electron configuration for positively charged atoms ?
- remove electrons from subshell of highest n value
- if multiple subshells are tied to highest n value , use highest l value
Paramagnetic
Materials composed of atoms with unpaired electrons will orient their spin to align with the magnetic field and will be attracted to the magnetic field
Diamagnetic
Materials that have atoms that have paired electrons and so they are slightly repelled by the magnetic field
Valence electron rules
Groups 1 to 2- only the highest s subshell electrons are the valence electrons
Groups 3 to 12 - electrons are highest in s and d
Groups 13 to 18 - electrons are highest in s and p
Lanthanides and actinides - valence electrons are those in highest f and s shells
