Atomic Structure Flashcards
2- Structure and Bonding
subatomic particles found in the dense nucleus of an atom
protons and neutrons
surrounds the dense nucleus
electrons
most of the mass is in the _________
nucleus
most of the volume is in the _____
electron cloud
indicates the total number of protons and the number of neutrons present in an atom
mass number
states the number of protons present in an atom
atomic number
atoms with the SAME number of protons but DIFFERENT numbers of neutrons
isotopes
almost 99% of the carbon found in nature
12C
the exact location of the electron
CANNOT be known; ONLY the electron density can be known
Quantum Mechanical Model
the probability that the electron will be in a certain region of space (orbital) at a given instant
electron density
Where do electrons move instead of circling around the nucleus in fixed orbits?
orbitals
each orbital has a characteristic _ and _.
shape, size (energy)
used to describe orbitals
Quantum Numbers
4 quantum numbers
- Principal
- Azimuthal/Angular Momentum
- Magnetic
- Electron Spin
symbol for Principal quantum number
n
symbol for Azimuthal/
Angular Momentum quantum number
l
symbol for Magnetic quantum number
m_l
symbol for Electron Spin quantum number
m_s
- indicates the main energy level or shell (size) of an electron in an atom
- represents the average distance of the electron from the nucleus
Principal
determines the shape (subshell) of the orbital
Azimuthal/
Angular Momentum
specifies the orientation of the orbital in space
Magnetic
describes the spin (direction) of an electron within an orbital
Electron Spin
values can be any positive integer and indicates the energy level or shell where electrons are located
Principal
ranges from 0 to (n-1) / s, p, d, f; corresponds to different sublevels within each principal energy level
Azimuthal/
Angular Momentum
ranges from -l to +l and defines the number of orbitals present within a sublevel
Magnetic
can have one of two possible values: +1/2 (spin up) or -1/2 (spin down).
Electron Spin
number of orbitals and electrons in s-subshell
one orbital, 2 electrons
number of orbitals and electrons in p-subshell
three orbitals, 6 electrons
number of orbitals and electrons in d-subshell
five orbitals, 10 electrons
number of orbitals and electrons in f-subshell
seven orbitals, 14 electrons
shape of s orbital
spherical
shape of p orbital
dumbbell
shape of four of the five d orbitals
cloverleaf
shape of the fifth d orbital
elongated dumbbell with a doughnut around its middle
describes where electrons are located around the nucleus of an atom
Electron Configuration
describes the orbitals occupied by the atom’s electrons when they are all in the available orbitals with the lowest energy
Ground-state electron configuration
- Electrons fill the lowest energy orbitals available before moving to higher energy orbitals.
- This principle dictates the order in which electrons occupy atomic orbitals.
Aufbau Principle
- Electrons prefer to occupy degenerate orbitals (orbitals of the same energy) singly with parallel spins before pairing up.
- This maximizes the total electron spin and stabilizes the atom.
This requires single occupancy before pairing.
Hund’s Rule
- No two electrons in a atom can have an identical set of four quantum numbers.
- This means an orbital can hold a maximum of two electrons, and then the electrons must have opposite spins, +1/2 and -1/2.
Pauli Exclusion Principle
This principle states that it is impossible to simultaneously know the exact position and momentum (or velocity) of a particle, such as an electron.
Heisenberg’s Uncertainty Principle
electrons below the outermost shell
Core Electrons
electrons in the outermost shell
Valence Electrons
