BONDING
Shapes of molecules
VSPER THEORY
Polarity
Dot and cross diagrams representing ionic and covalent bonding
Metallic bonding and giant metallic structure
Giant ionic and covalent structures
Simple molecular structure
This theory assumes that the molecules would have a geometrical shape that would decrease the repulsion between their electrons in the valence shell of that atom
STRUCTURE SHAPES
Trigonal planar
Trigonal pyramidal
V-shaped/Bent
Tetrahedral
Linear
Trigonal bipyramidal
Intermolecular forces between familiar and unfamiliar forces
Dipole-Dipole forces
Melting and boiling points are influenced by intermolecular forces
EXAMPLES:
Electronegativity and Positions of atoms on the periodic table
Description
Definition of Molecules
Why they are gases at room temperature
Predicting electronegativity based on polarity values
Polar covalent, Non-polar covalent, ionic and dative covalent
How we know ions exist
What we can obtain from electron density maps
Definition of polarization of atoms
Which types of elements form covalent bonds when they react with each other?
Why is the covalent bond in an oxygen molecule a double bond?
Draw a dots and cross diagram of carbon dioxide
Which kind of elements form ionic bonds when they react together
What is the charge on an aluminum ion? What is the charge on a nitride ion?
Could you draw a dot and cross diagram of sodium sulfide?
How would you describe metallic bonding?
Could you draw a particle diagram to represent the bonding in magnesium?
Why are metals malleable?
Why do metals conduct electricity?
How would you describe giant covalent structure?
Example of substances that have giant covalent structures
Why do giant and covalent structures have high boiling and melting points?
How would you describe a giant ionic structure?
Draw a 3d diagram to represent the structure of sodium chloride
Why giant ionic structures conduct electricity when they are aqueous or liquid but not when solid?
Covalent bonds usually occur between nonmetals. For example, in water (H2O) each hydrogen (H) and oxygen (O) share a pair of electrons to make a molecule of two hydrogen atoms single bonded to a single oxygen atom.
Because in order for an oxygen atom to have a full outer shell, it requires two electrons. Double bonds are shown by two lines joining the atoms together
In an ionic bond, the atoms are bound together by the electrostatic forces in the attraction between ions of opposite charge. Ionic bonds usually occur between metal and nonmetal ions. For example, sodium (Na), a metal, and chloride (Cl), a nonmetal, form an ionic bond to make NaCl.
When it becomes an ion, it loses 3 electrons, leaving behind only 10. Now the charge is +3
the electron density map (EDM) provides much clearer insight into the uncertainties in the model than does merely examining the model itself
The electronegativity of an atom depends on both the atomic number and the distance of the valence electron from the nucleus. Electronegativity increases along the period from left to right and decreases down the group in general. Fluorine is the most electronegative element and cesium is the least electronegative.
Electronegativity is the tendency of a bonded atom to attract electrons to itself. The difference in electronegativity ( Δ EN) between bonded atoms can indicate whether the bond is nonpolar, polar covalent, or ionic.Generally, the farther apart two elements are on the periodic table, the more ionic the bond character, and the closer together they are, the less ionic the bond is.
Polar Covalent
The intermolecular forces between the nucleus (+) and electrons (-) in the outer shell of an atom are weak, therefore they are likely to leave and get attracted to an atom with stronger force of attraction and intermolecular force, showing that ions exist
When the electron cloud of an atom is shifted from its original position it is said that the atom is polarised. This is influenced by an external charge so that the cloud isn't centered on the nucleus
When there is a covalent bond between two atoms but the electrons aren't shared equally - we know an atom is polar covalent because it doesn't have a symmetrical shape
Non-polar covalent
Is when the electrons are shared equally between two atoms - we know this if the shape of the atom is symmetrical
Ionic bonds
Electrons are transferred from one atom to another resulting in the formation of positive and negative ions.
The electrostatic attractions between the positive and negative ions hold the atoms together.
Dative bonds
A dative bond is a covalent bond which both of the electrons came from the same atom. Dative bonds are shown using arrows, the arrow points from the atom donating the lone pair to the atom accepting it.
Hydrogen bonds
London dispersion forces/Van der Waals
These forces occur when the partially positively charged part of a molecule interacts with the partially negatively charged part of the neighboring molecule.
This interaction occurs specifically between a hydrogen atom bonded to either an oxygen, nitrogen, or fluorine atom.
The partially positive end of hydrogen is attracted to the partially negative end of the oxygen, nitrogen, or fluorine of another molecule.
These forces are present between all molecules- and they are the weakest force of attraction. The strength of this force depends on the number of electrons an atoms has.
A molecule has a higher boiling and melting point based on the strength of its intermolecular attractions. The melting and boiling points are influenced by two factors, 1-the type of bonds they have and 2-the number of bonds [of dipole-dipole, hydrogen or van der Waals] that they have.
The strongest intermolecular force are hydrogen bonds, followed by dipole-dipole with van der Waals being the weakest. If a molecule has many hydrogen bonds, it is going to require a massive amount of energy to break those bonds
Octahedral
180°, e.g. CO2
104.5°, e.g. H2O
120°, e.g. BF3
107°, e.g. NH3
109.5°, e.g. CH4
90° & 120°, e.g. PCl5
90°, SF6
These bonds are formed in metal lattices were the electrons are delocalised and there is a electrostatic force of attraction between the positive metal ions and the delocalised electrons
Metals are malleable because of their structure. When there is a force placed on metals, due to their arrangement of their atoms, their atoms are able to slide/roll over each into different positions without breaking their metallic bond which makes them malleable
Metals conduct electricity because there are delocalised electrons present in the structure of metals. And because these electrons are free to flow throughout the metal's structure, they allow electricity to pass and therefore are good conductors of electricity
They are giant lattices of non-metals which are bonded together using covalent bonds - this causes them to have very strong structures because they are bonded with many adjacent atoms, which also makes them insulators of electricity
Diamond, Graphite, Silicon Dioxide
Because the atoms are bonded to many other atoms - this increases the number of bonds they had which would require more energy to break them therefore they would have high boiling and melting points
They are made up of endlessly repeating molecules of an ion - this makes them to become a lattice and form a giant ionic structure
Because when they are solid, their positive and negative atoms are attracted to each other because of electrostatic forces of attraction due to the bonds they have with their opposite charged atoms. When they are broken, some of these bonds are broken which would make the giant ionic lattice to allow electricity to pass through when they are in liquid or aqueous state.
They are made up of a small number of molecules with strong intramolecular forces and are usually bonded together by covalent bonds - they usually have weak intermolecular forces which is why they come in small and simple molecular structures
molecules are the simplest particle of a chemical. They are bonded together using different bonds such as covalent and ionic bonds.
Because they have a small number of bonds, they require less energy in comparison to large chemical compounds, therefore their bonds are going to break at a lower temperature compared to giant structures.