Atomic and molecular structure Flashcards
Atom
Basic building block of matter representing the smallest unit of a chemical element. Composed of some atomic particles protons, neutrons and electrons. Nucleus at the core containing protons and neutrons. Electrons in regions of space called orbitals
Dalton’s atomic theory
- All elements are composed of very small particles called Adams. All Adams of an element are identical in size, mass, chemical properties
- All compounds are composed of atoms of more than one element
- A chemical reaction Involves the separation, combination, or rearrangement of atoms. It does not result in the creation or destruction of atoms
Proton
Positive charge 1 amu = 1 Da Atomic number (Z)
Neutron
No charge
1 amu
Isotopes
One element which has different numbers of neutrons but the same number of protons
Electron
Negative charge
Valence electrons
Electrons in the electron shell farthest from the nucleus. Have weaker attractive force of the positively charged nucleus
Ion
A positive or negative charge on an atom due to the loss or gain of electrons
Atomic number (Z)
The number of protons/electrons in a neutral atom
Mass numbers (A)
The total number of protons and neutrons
Molecular weight
The weight in grams per one mole of a given element
Mole
A unit used to count particles
Represented by Avogadro’s number
Avogadro’s number
6.02 x10^23
How many atoms of carbon are in 12 g of carbon-12
Standard atomic weight
A weighted average of all the isotopes of an element found naturally on earth
Quantum theory
Max Planck
Energy admitted as electromagnetic radiation from matters comes in discreet bundles called quanta
E = hf
Planck’s constant (h)
6.626 x 10^-34 Js
Bohr Model
An electron can exist only in certain fixed-energy states. A central proton around which electrons travel in a circular orbit and be centripetal force acting on the electron is the electrical force between positively charged protons and negatively charged electrons
Ground state
The lowest energy state of an electron
Atomic emission spectrum
The line spectrum of light at specific frequencies where each line on the emission spectrum corresponds to a specific electronic transition. Unique for each element
Baller series
Transition from n>2 to n=2
Visible and ultraviolet
Lyman series
Transition from n>1 to n=1
Ultraviolet
Paschen series
Transition from n>3 to n=3
Infrared
Atomic absorption spectrum
The expectation of electrons in a particular element results in energy absorptions at specific wavelengths. Wavelength of absorption correspond directly to wavelengths of the Mission
Heisenberg uncertainty principle
It is impossible to simultaneously determine with perfect accuracy the momentum in the position of an electron
Orbitals
A representation of the probability of finding an electron within a given region. A specific region with in a sub shell that may contain no more than two electrons
Pauli exclusion principle
No two electrons in a given atom can possess the same set of four quantum numbers
Energy state
The position an energy of an electron described by its quantum numbers
Principal quantum number, n
The shell where an electron is present in an atom
Azimuthal quantum number, l
Angular momentum quantum number
The subshells or sublevels that occur within each principal energy level
0 to n-1
4l+2
The maximum number of electrons that can exist within a sub shell
Magnetic quantum number, ml
The orientation of the orbital in space
l to -l
2n^2
The maximum number of electrons in an electron shell
Spin quantum number, ms
Intrinsic angular momentum
1/2 and -1/2
Parallel spins
Same ms value
Paired spins
Different ms values
Electron configuration
The pattern by which subshells are filled and the number of electrons within each principal level and some shell are designated
Aufbau principle
Subshells are filled from lowest to highest energy
n+l rule
The lower the sum of the first and second quantum numbers, the lower the energy of the sub shell
Hund’s rule
Within a given some shell, orbitals are filled such that there are a max number of half filled orbitals with parallel spins
Paramagnetic
Unpaired electrons. A magnetic field will align the spins of these electrons in weekly attract the atom to the field
Diamagnetic
No unpaired electrons. Are slightly repelled by a magnetic field
