Chapter 6 - Claire Flashcards
What Δ EN values create an ionic bond?
1.7 to 3.3
What Δ EN values create a covalent bond?
0 to 1.7
Where is atomic radius the largest?
Bottom left of the periodic table
Are cations smaller or larger than the neutral atom?
Smaller
Are anions smaller or larger than the neutral atom?
Larger
Def. the net positive charge experienced by an electron in a multi electron atom, representing less than the full nuclear charge as inner electrons repel outer electrons, offsetting some of the nucleus’s inward pull(I.e. shielding effect)
Effective nuclear charge
Def. the repulsive action of inner core electrons in outer valence electrons, effectively reducing the nucleus’s inward pull, causing the atom to increase in size
Shielding effect
Coulomb’s law states that the _______ of force depends directly on the amount of ____________
Strength, electrostatic charge
Which two elements have no shielding effect?
Hydrogen and helium
What are the four types of charge?
- Proton-proton repulsion
- Neutron-proton attraction (residual strong force)
- Electron-electron repulsion
- Nucleus-electron attraction
Def. an expression of the size of an atom, representing the typical distance from the center of its nucleus to the boundary of its electron cloud
Atomic radius
Def. an estimate of the size of an atom, based on half the distance between covalently bonded atoms
Covalent radius
Def. an estimate of an the size of a metal atom based on half the distance between the nuclei of adjacent atoms in a metal lattice
Metallic radius
What affects an electron cloud/ an atoms size?
- Number of occupied shells
2. Amount and type of charge
Def. predictable and regular patterns of cyclical change in elemental properties throughout the periodic table, moving either vertically or horizontally
Periodic trends
Def. the amount of energy required to remove the most loosely held electron from a gaseous atom to form a cation, or from a cation to increase its positive charge
Ionization energy
Where are electrons held the most loosely?
Bottom right of the periodic table
Def. a chemical property that describes an atom’s (or a group of atoms’) ability to attract electrons towards itself
Electronegativity
Def. the change in energy when an atom gains an electron to form an anion, or when an anion gains another electron, increasing its negative charge
Electron affinity
The higher the electronegativity, the higher the ____________
Electron affinity
def. A numerical value representing the difference in the electronegativities of two atoms
ΔEN
def. A covalent bond between non-metal atoms with the same electronegativities, where
electron sharing is equal between them
Nonpolar covalent bond
Are electrons ever transferred to a different atom?
No, they only effectively transfer because there is always some sort of electronegativity
def. A covalent bond between two non-metal atoms in which electron sharing is sufficiently
unequal that the bond displays significant and meaningful ionic nature
Polar covalent bond
Where is the electron sharing is equal or nearly equal between the atoms and the
bond has predominantly covalent character with little to no ionic character?
Nonpolar bonds
Where is the electron sharing is disproportionately uneven enough that the bond has
predominantly ionic character, with very little covalent character?
ionic bonds
def. The non-integer charge values at the ends of a polar covalent bond, due to the uneven
distribution of electron density within the bond
Partial ionic charges (δ+, δ–)
Where is the electron sharing is uneven enough that
the covalent bond has some ionic nature – more than a nonpolar bond, but less than an ionic?
polar bonds
what Δ EN values form a polar bond?
0.4-1.7
what Δ EN values form a non-polar bond?
0-0.4
def. A simplified diagram that communicates molecular structure using:
▪ An element’s symbol to represent its nucleus and core electrons
▪ Dots to represent any nonbonding electrons in the valence shells
▪ Lines to represent the pairs of bonding electrons in chemical bonds
Lewis structure
What are Lewis structures of individual atoms called?
electron dot structures
when orbitals hybridize they become ________
equivalent
def. describes an atom’s combining power, often in terms of how many chloride anions it can ionically bond with
valency
for metals, valency represents how many electrons it will _______
lose
for non-metals, valency represents how many electrons it will _______
gain
Apart from how many electrons a non-metal will gain, what does valency represent for non-metals?
how many covalent bonds it will form
the lewis structure of _______ compounds show the component ions and the ratio between them
ionic
for the lewis structures of ionic compounds, you must surround the ions with _______ brackets and ___________
square, superscript to represent their ionic charges
ionic compounds exist in what way?
ionic crystal lattices
covalent compounds exist in what way?
as separate and distinct molecules
Valence electrons can be either _______ or _______
bonding or non-bonding
def. any pair of valence electrons that are non-bonding, as atoms don’t share them with other atoms
lone pair
lone pairs may _______ or _______ because of bond formation
form or disperse
hydrogen obeys the ____ rule in molecules
duet
def. an observational rule in chemistry that says the valence shells of the first-period elements hydrogen and helium can hold a maximum of two electrons, never more
duet rule
def. An observational rule of thumb in chemistry that says main-group elements from
periods 2 to 7 seek to have eight electrons in their valence shell
octet rule
What are the exceptions to the octet rule?
Boron, Beryllium, Aluminium, Hydrogen and Helium
What periods can exceed the octet rule?
Periods 3-7
In a Lewis structure, for binary compounds which element is usually the central atom?
the one with the lower electronegativity
def. Covalent bonding between two atoms who share more than two electrons
Multiple bond
def. A configuration of elements from periods 3 through 7, in which their valence shells
expand past eight electrons as the central atom, as they can incorporate d orbitals
expanded octet
when a molecule’s central atom takes on more than eight electrons, what do we call the molecule?
Hypervalent molecule
def. Different, but equivalent Lewis structures of the same molecule, showing all the
possible double bond locations, connected by a double-headed arrow
resonance structures
def. Electrons in a molecule, ion or solid metal that aren’t associated with a single atom or
covalent bond, allowing them to be co-valent to more than two atoms
Delocalized electrons
When atoms share electrons unevenly enough that the the bond takes on ionic character, the atoms develop _________
partial charges
the _____ electronegative atom gains electron density and develops a partial negative charge δ–
more
the ______ electronegative atom loses the electron density, and develops a partial positive charge δ+
less
def. describes the separation of opposite charge
electric dipole
def. A vector quantity that expresses a bond’s polarity, showing the separation of opposing
charges (an electric dipole), and the directionality of that separation (a moment)
bond dipole moment
def. o A molecule that has an overall, or net dipole moment, because of its bond polarities and
its molecular geometry
polar molecule
def. A vector quantity expressing a molecule’s overall polarity, being the net dipole moment
resulting from the vector addition of the molecule’s individual bond dipole moments
molecular dipole moment
when can a molecule be polar?
A molecule can only be polar if it contains polar bonds and
is asymmetrical, in either shape, composition or both
def. Attractive forces that exist within a molecule or compound, holding the atoms together
Intramolecular forces
def. Forces, mainly attractive, that exist between molecules and neighbouring particles, be
they other molecules, atoms or ions
Intermolecular forces
def. The attractive force that exists between the partial positive charge of one polar
molecule and the partial negative charge of another
dipole-dipole force
dipole-dipole forces exist between polar molecules that have ______ molecular dipole moments
permanent
def. An electrostatic attraction that forms between the partially positive hydrogen in a highly polarized bond (usually H–N, H–O and H–F) and the negative lone pair on a nearby atom ▪ Stronger than a typical dipole-dipole interaction because it has some covalentbond character of electron sharing
Hydrogen bond
In polar molecules, quantum mechanical uncertainty affects the
________ of the molecular dipole moment
strength
In nonpolar molecules, quantum mechanical uncertainty affects the ________ of a
molecular dipole
existence
def. A weakly attractive force that forms when nonpolar molecules gain temporary dipole
moments
London dispersion force
