2. Structure and Bonding [revised] Flashcards
explains that electrons are in 3-dimensional shaped electron clouds that represent the probability of an electron’s location.
QUANTUM THEORY
explains that the electrons are in orbits or shells.
BOHR’S THEORY
the idea of an electron “orbiting” the
nucleus like planets orbiting the sun.
orbit
electron clouds that represent the shape of probability for an electron’s location.
orbitals
tells about the detailed location of
electrons in an atom, the specific electron
orbitals that the electrons are found.
electron configuration
How many orbitals are in the fourth
energy level?
The 4th level contains s, p, d, and f orbitals,
so the TOTAL NUMBER OF ORBITALS is 16.
How many orbitals of each type are
there? For s, p, d, and f?
s – 1
p – 3
d – 5
f - 7
__% of more than 30 million chemical compounds contain carbon.
90%
Who is often credited as the father of modern atomic theory?
JOHN DALTON
TRUE OR FALSE
- Indivisibility of atom
- All atoms of the same element are
identical - Different elements have very different
types of atoms or differ in all respects
- wrong
- wrong, isotopes
- wrong, isobars
Who proposed the planetary model of the
atom?
Niels Bohr
TRUE OR FALSE
- Electrons orbit the nucleus in
orbits that have a set size and energy. - The energy of the orbit is related to its size.
- Radiation is absorbed or emitted when an electron moves from one orbit to another.
- wrong
- true
- true
states that there is an inherent uncertainty in the act of measuring a variable of a particle
Heisenberg Uncertainty Principle
model when electrons where originally thought to orbit around the nucleus in defined paths
electron orbit model
model when it was discovered that electrons move in waves in a defined space called an electron cloud
electron cloud model
Structure of an atom: small diameter size
2 x 10-10 m = 200 pm
very dense; contains protons and neutrons
▪ protons (positively charged)
▪ neutrons (neutral)
▪ small (10-15 m)
nucleus
▪ negatively charged
▪ located in space remindful of a cloud (10-10 m) around nucleus
electrons
number of protons in nucleus
All atoms of same element have the same Z value
atomic number (Z)
number of protons plus neutrons
mass number (A)
atoms of the same element with different numbers of neutrons and thus different A.
isotopes
_______ of an element is weighted average mass in atomic mass units (amu) of an element’s naturally occurring isotopes.
The atomic mass
four different kinds of orbitals for electrons based on those derived for a hydrogen atom
s, p, d, f
most important orbitals in organic and biological chemistry
s and p orbitals
spherical, nucleus at center
s orbitals
dumbbell-shaped, nucleus at middle
p orbitals
elongated dumbbell-shaped, nucleus at center
d orbitals
tetrahedral, nucleus at center
f orbitals
____ are grouped in shells of increasing size and energy
orbitals
Each orbital can be occupied by how many electrons
two electrons
First shell contains one s orbital, denoted as 1s, holds only ___ electrons
2 electrons
Second shell contains one s orbital (2s) and three p orbitals (2p), holds ____ electrons
8 electrons
Third shell contains an s orbital (3s), three p orbitals (3p), and five d orbitals (3d), holds __ electrons
18
Lobes of a p orbital are separated by region of zero electron density, which is called a _____.
node
▪ lists orbitals occupied by its electrons.
(i.e., lowest energy arrangement)
Ground-state electron configuration
states that the lowest-energy orbitals must be filled first
Aufbau (“build-up”) principle
states that only two electrons can occupy an orbital, and they must be of opposite spin to have unique wave equations
Pauli exclusion principle
states that if two or more empty orbitals of equal energy are available, electrons occupy each with spins parallel until all orbitals have one electron
Hund’s rule
_____ bonds in salts form by electron transfers
ionic
(electron dot) show valence electrons of an atom as dots
Lewis structures
(line-bond structures) have a line drawn between two atoms indicating a 2 e- covalent bond.
Kekulé structures
Valence electrons not used in bonding are called
nonbonding electrons, or lone-pair electrons
forms when two atoms approach each other closely so that a singly occupied orbital on one atom overlaps a singly occupied orbital on the other atom
Covalent bond
▪ Two models to describe covalent bonding:
▪ Valence bond theory
▪ Molecular orbital theory
Electrons are paired in the overlapping orbitals and are attracted to nuclei of both atoms
Valence Bond Theory
Who independently observed that carbon always has four bonds
Kekulé and Couper
Who proposed that the four bonds of carbon have specific spatial directions
van’t Hoff and Le Bel
s orbital and three p orbitals combine to form four equivalent, unsymmetrical, tetrahedral orbitals
Bond angle: 109.5°: the tetrahedral angle.
sp3 hybrid orbitals
2s orbital combines with two 2p orbitals, giving 3 orbitals. This results in a double bond.
▪ 120° angles
▪ The remaining p orbital is perpendicular to the plane
sp2 hybrid orbitals
where electrons are most likely to be found (specific energy and general shape) in a molecule
▪ Additive combination (bonding) MO is lower in energy
▪ Subtractive combination (antibonding) MO is higher in
energy
molecular orbital (MO)
The π _____ MO is from combining p orbital lobes with the same algebraic sign
π bonding
The π _____ MO is from combining lobes with opposite signs
π antibonding
_______ structures don’t have C-H or C-C single bonds shown. They are understood.
Condensed structures
charged nucleus containing positively charged protons and neutrally charged neutrons surrounded by negatively charged electrons
Atom
Electronic structure of an atom is described by
wave equation
__ orbitals are spherical, __ orbitals are dumbbell-shaped
s orbitals
p orbitals
electron pair is shared between atoms
Covalent bonds
electron sharing occurs by overlap of
two atomic orbitals
Valence bond theory
bonds result from combination of atomic orbitals to give molecular orbitals, which belong to the entire molecule
Molecular orbital (MO) theory
Circular cross-section and are formed by
head-on interaction
Sigma (σ)bonds
“dumbbell” shape from sideways interaction of p orbitals
Pi (π) bonds
In single bonds with tetrahedral geometry, carbon has four ____ hybrid orbitals
sp3 hybrid orbitals
In double bonds with planar geometry, carbon uses three equivalent ___ hybrid orbitals and one unhybridized p orbital
sp2 hybrid orbitals
Carbon uses two equivalent __ hybrid orbitals to form a triple bond with linear geometry, with two unhybridized p orbitals
sp hybrid orbitals
Atoms such as nitrogen and oxygen hybridize to form strong, oriented bonds
▪ The nitrogen atom in ammonia and the oxygen atom in water are ___ hybridized
sp3 hybridized
