Atomic Structure and Bonding Flashcards
Charge on an electron
Negative
Charge on a nucleus
Positive
Systems behave in such a way as to…
…reduce stored energy.
Electrostatic forces in an atom
Like charges repel. Electrons have negative charges. They experience repulsion from each other.
Unlike charges attract. Electrons experience attraction towards nuclei.
Electrons have magnetic fields.
If we try to push two electrons together, they will tend to align anti-parallel.
No two electrons can occupy the same state.
This means two electrons cannot both be in the same “place” with the same energy and with the same spin states all at the same time.
Electrons are quantum objects
It is far more useful for us to know the energy of electrons, so we sacrifice our accurate knowledge of electron location and deal with “clouds” of probability, the shape of which tells us where we expect to find an electron if we measured position. We call these “orbitals”.
Ground state
Lowest energy state for an atom.
Orbitals
Each orbital can contain no electrons, one electron or two electrons.
Core Charge
the charge on the atom or ion in the absence of all outer shell electrons. Also known as effective nuclear charge, this gives an indication of the attraction that valence electrons have towards the nucleus
Atomic Radius
the distance from the nucleus to the outermost electrons, measured as half the distance of a single covalent bond between two identical atoms
Electronegativity
a measure of the strength of the attraction between atoms of that element and electrons participating in bonding.
Electron Shielding
the repulsive force exerted by inner shell electrons on outer shell electrons, pushing them away from the nucleus
Molecule
Smallest unit of a simple covalent substance that retains the chemical and physical properties of that substance.
Defined formula that describes the number of atoms in that particle. Atoms positioned in a defined arrangement.
Covalent bond
Strong electrostatic force of attraction between two atomic nuclei and a shared pair of electrons between those atoms.
Electrons in covalent bonds and lone pairs are localized
they are held in place attracted to positive charges on either side. They cannot drift off.
Covalent bonds are directional
they are in a well-defined place.
Electron geometry
We can work this out from the fact that each group of electrons will repel from all the other groups of electrons around the same atom in a molecule.
Molecular geometry
We can work this out from the electron geometry and the types of groups of electrons.
Intramolecular
Bonding within molecules- covalent bonds
Intermolecular
Bonding between separate molecules
Dispersion force
At any instant charge distributions are not symmetrical so there will be weak fluctuating “instantaneous” dipoles.
The negative pole will attract a nucleus in another species (thing) so will both cause and attract a positive pole in the other species.
Dipole-Dipole force
Large difference in electronegativity between the atoms on each side of a covalent bond will result a “polar” bond.
An asymmetric shape of a molecule containing polar bonds will give a molecule that has an overall resultant polarity.
The negative pole attracts to positively charged regions of other species, the positive pole attracts to negatively charge regions of other species.
Hydrogen bond
Electrostatic force of attraction between a hydrogen atom which is covalently bonded to a more electronegative atom or group, and another electronegative atom with a lone pair of electrons.
