Atomic Structure and Bonding Flashcards
atoms are comprised of
protons
electrons
neutrons
protons
the number of protons in the nucleus identifies the atom and therefore the element
neutrons
can vary without changing the element
electrons
found in clouds/orbitals around the nucleus of the atom, determines the chemistry of the element
nuclear strong force
holds protons and neutrons together
very strong but short ranged interaction
ions
formed when electrons are added or removed from a neutral atom, but the protons remain the same
carry a charge
negative ions
contain more electrons than protons
positive ions
contain fewer electrons than protons
work
energy required to move from the lower energy state
potential energy
energy expended to return to lower energy state
ionic bonding
donation of electrons that results in charged atoms
sodium loses an electron to a chlorine atom and makes Na positive and chlorine negative
covalent bonding
electrons are shared between atoms
substances are held together by interactions between atomic orbitals and the electrons occupying the orbitals on adjacent atoms
metallic bonding
metals have low ionization energy - results in delocalized valence electrons, creating a high energy sea/cloud of electrons
electrons hold the positive atoms in place, giving material structure and certain characteristics
sharing of free electrons among a structure of positively charge ions
electronegativity
the ability of an atom in a molecule to attract shared electrons
electrons are pulled towards the more electronegative atoms
Linus Pauling polarity scale
<0.4 = zero –> pure covalent
0.4-1.7 = intermediate –> polar covalent
>1.7 = large –> ionic
Linus Pauling polarity scale trend
as covalent character increases, ionic character decreases
diatomic molecule
H2
non polar
symmetrical electron sharing
non-symmetrical molecule
HCl
polar
unsymmetrical electron sharing
secondary bonding/intermolecular forces
non-covalent bonds
electrons are not shared
result of charge variations
weaker
two main types: Hydrogen bonds (dipole-dipole - unequal bond sharing), Van der waals (VDW) bonds (dispersion forces - equal bond)
hydrogen bonds
results from electrostatic attraction between permanent dipoles created by unequal sharing of electrons in covalent bonding
responsible for density of liquid water being higher than density of ice
Van der Waals forces
results from electrostatic attraction between temporary dipoles created by nearly equally shared electrons in covalent bonding
responsible for holding collections of molecules together in bulk materials
