Bonding Flashcards
Noble gases are the most…
…unreactive of all the elements.
Noble gases have little or no tendency to…
…form bonds to other atoms.
Except He, all noble gases possess a…
…ns^2 np^6 configuration
Elements that lack the ns^2 np^6 configuration of noble gases tend to…
acquire it (i.e. GAIN, LOOSE or SHARE electrons) through chemical reactions, resulting in formation of compounds, where each element has a FULL and stable outer most electron shell
Elements of the d and f blocks also lose or share electrons…
…Octet Rule does not apply to them.
When forming compounds elements lose, gain, or share electrons so their…
…configurations become identical to the nearest noble gas in the periodic table
What is an ion?
atom (or group of atoms) electrically charged (+ve or –ve) as a result of
the loss or gain of an electron
Whats a cation?
Ions with a positive charge. (loses an electron)
Whats an anion?
Ion with a negative charge (gains an electron)
Atoms can gain or lose…
…one, two, or three electrons.
Electron loss or gain doesn’t happen in isolation, but are…
…parallel processes
Ionic bonds are…
…electrostatic attractions between cations and anions
(Lewis structures can help visualise the process)
An ionic bond is formed only between a…
… metal and a non-metal
i.e. group 1 & 2 elements (metals) with group 6 & 7 elements
WHat groups on the periodic table are metals?
group 1 and group 2
WHat groups on the periodic table are non metals?
group 6 and group 7
the attraction of oppositely charged ions draws them together releasing energy and causing the ions to form a…
…solid array or lattice
What is lattice energy?
a measure of the stabilisation
caused by oppositely charged ions forming a solid lattice.
The term “molecule” is not used when…
…referring to ionic substances
A covalent bond consists of …
…a pair of electrons shared between two atoms as the atoms attempt to acquire noble-gas configurations.
The covalent bond is the…
…predominant chemical bond
The sharing of a pair of electrons =
single (covalent) bond
Atoms can complete octets by…
…sharing more than one pair of electrons
What is the Valence Shell Electron Pair (VSEPR) Model?
- Based on the idea that electron pairs will repel each other
- The electron pairs will arrange themselves around the central atom as far apart as possible, to minimise the repulsion between them
What does VSEPR Model stand for?
Valence Shell Electron Pair (VSEPR) Model
What is not shown by the Lewis structure?
The shape of the molecule is not shown by the Lewis structure
What is the electron domain geometry of minimum repulsion for water?
tetrahedral
In the VSEPR Model, a bond and a nonbonding pair of electrons define …
…locations where electrons are
likely to be found and hence are called electron domains
Why do electrons repel each other?
bcus they are negatively charged bitch
Because electrons are negatively charged they…
…repel eachother
The best arrangement of a given number of electron domains is…
…the one that minimises the repulsions between them
Whats the MOLECULAR geometry for water?
BENT
Why is the shape of water so important?
life would not be possible if it
were not bent
In H20 (water), is the arrangement of atoms (molecular geometry) linear?
No!
Ionic bonds and nonpolar covalent bonds represent…
…two extremes.
How many electron domains in water?
4
If the two atoms that constitute a covalent bond are identical then there is an…
…equal sharing of electrons.
Covalent bonding involves the…
…SHARING of electron pairs.
SHARING IS CARING BITCH
The electron pair that makes up the covalent bond is…
… equally shared by the two atoms
In ionic bonds (such as in NaCl) there is …
…no sharing of electrons.
the 3s electron of Na is completely transferred to Cl
Ionic bonding involves…
…the COMPLETE TRANSFER of electrons.
What is an example of a Non polar covalent bond?
The chlorine gas molecule
Cl2 is nonpolar covalent.
When does a non polar covalent bond occur?
When the two atoms that constitute a covalent bond are identical, resulting in an equal sharing of electrons.
If the two atoms that constitute a covalent bond are not identical then…
…there can be an unequal sharing of electrons
When does a polar covalent bond occur?
When the two atoms that constitute a covalent bond are not identical, resulting in an unequal sharing of electrons.
The charge difference in polar covalent bonds is a result of…
…the unequal attractions the atoms have for their shared electron pair and results in a dipole
A polar bond results when…
…one of the atoms exerts a greater attraction for the bonding electrons than the other
If this difference in relative ability to attract electrons is large enough, an ionic bond is formed
What is electronegativity?
Electronegativity is the ability of an atom in a molecule to attract electrons to itself
Electronegativity increase as you go…
…Up the periodic table or from left to right on the periodic table (across the periods)
Electronegativity correlates with…
…atomic radii
What does electronegativity result in?
Correlates with atomic radii –> greater nuclear effect (Zeff) –> valence electrons pulled closer to the nucleus.
Intermolecular electrostatic
interactions means water is…
…liquid at room temperature
(0 – 100 degrees C)
VSEPR model is good at…
…predicting molecular shapes, but does not explain why bonds exist between atoms.
Lewis theory states that …
…covalent bonding occurs when atoms share electrons, which concentrates the electron density between the nuclei
What are sigma (σ) bonds?
Covalent bonds in which the electron density is concentrated symmetrically
about the internuclear axis
What are pi (π) bonds?
a type of bond which results from sideways overlap of two p orbitals, in which the overlap regions lie above and below the internuclear axis
two regions of overlap constitute a single…
… pi (π) bond
In almost all cases, single bonds are […] and additional bonds are […].
In almost all cases, single bonds are s-bonds and additional bonds are p-bonds.
Like electron orbitals around an atom…
…bonds have different energy levels.
s-orbitals have lower energy than…
…p-orbitals
How / in what order do electron orbitals fill?
s-orbitals have lower energy than p-orbitals > electrons fill at the lowest energy
level first:
s orbitals fill before p
covalent bonds follow the same principle (where double/triple bonds are formed):
σ-bonds are lower energy than π-bonds
irrespective of atomic orbitals…
…sigma bonds form before pi bonds.
Carbon is the…
…skeleton of biological molecules.
Carbon has the ability to form…
…polymerise (form long chains)
This is the basis of all biological macromolecules.
Bond orbitals confer bond shape –>
–> bond shape confers molecule shape
Molecule shape is key to…
… life – carbohydrates, proteins, lipids, nucleic acid, hormones, vitamins……
