Electrons And Bonding Flashcards
Shell number/energy level
Principle quantum number
Atomic orbital
A region around the nucleus that can hold up to 2 electrons with opposite spins
Subshell
Groups of orbitals
Opposite spins
Help counteract the repulsion between negative charges of e-
4s sub shell
Fills and empties before 3D as once filled the 3D falls below the 4s subshell
Ionic bonding
Electrostatic attraction between positive and negative ions
Ionic melting and boiling points
High temperatures needed to provide the energy to overcome the strong electrostatic attraction between the ions ionic compounds have high melting and boiling points Higher ionic charge increases boiling point as stronger attraction between ions
Solubility of ionic compounds
Most dissolve in polar solvents such as water polar molecules break down the lattice and surround each ion in solution.
Large charges may be too strong for water to be able to break down the lattice structure the water will then not dissolve
Two processes for solubility
Ionic lattice must be broken down and water molecules must attract and surround the ions
Ionic electrical conductivity
Does not conduct as a solid but once melted or aqueous electrons are free to move and carry charge
Covalent bonding
The strong electrostatic attraction between A shared pair of electrons and the nuclei of the bonded atoms occurs between non-metal elements orbital overlap
Molecule definition
The smallest part of a covalent compounds that can exist whilst retaining the chemical properties of the compound
Boron bonding
Has three outer shells that can be pad forms three covalent bonds only six electrons in outer shell
Expanding the octet
From n=3
In sulphur phosphorus and chlorine depending on the number of unpaired electrons depends on how many bonds can form
Average bond enthalpy
A measurement of covalent bond strength the larger the value the stronger the bond. Always endothermic BENDO
Ammonia shaped
Pyramidal 107°
Water shape
Non linear
104.5
Electronegativity
The attraction of a bonded atoms for the pair of electrons in a covalent bond.
Dipole
Separation of opposite charges
Dipoles from polar bonds
Permanent dipoles- do not change
Intermolecular forces
Weak interactions between dipoles of different molecules
Responsible for the physical properties of the compound
London forces
Induced dipole dipole interactions
Three types of intermolecular forces
London forces weakest
permanent dipole interaction hydrogen bonding strongest
London forces working
Movement of electrons produces the changing dipole in a molecule
And instantaneous dipole will exist but its position is constantly shifting the instantaneous dipole induces a dipole on a neighbouring molecule
Temporary- the next instance dipole disappears
Strength on induced dipole interactions
Larger dipole- greater interaction
Stringer attractive forges
More electrons= larger induced dipoles=more energy needed to overcome
Permanent dipole interactions
Act between the permanent dipoles in different molecules
Simple molecular substances
Made up of simple molecules small units containing a definite number of atoms with a definite molecular formula in the solid-state form a simple molecular lattice where the molecules are held in place by weak intermolecular forces but the atoms within each molecule are bonded together strongly by covalent bonds
Melting points and boiling point a simple molecular substances
Low melting and boiling point as molecular forces are weak so easy to overcome but covalent bonds are strong and do not break
Simple molecular substances solubility
Can be polar or nonpolar nonpolar dissolve in nonpolar substances such as hexane when intermolecular forces be formed between the molecules and a solvent do not dissolve in polar solvents as intermolecular bonds within the solvent are too strong
Polar simple molecular substances may dissolve in polar- depends on strength of dipole. Some C chains too long C2H5OH dissolve in polar and non polar
Hydrogen bonds
Special type of permanent dipole interaction between molecules containing and electronegative atom with a lone pair (O N F) and a hydrogen attached to electronegative atom acts between lp and H strongest IM force
Anomalous properties of water
Solid is less dense than the liquid water has high melting points and boiling point and high surface tension
Ice vs water
Hydrogen bonds hold water molecules are part in an open lattice structure water molecules in ice a further apart then in water solid ice is less dense than water and floats
Water melting points and boiling point
Hydrogen bonds are extra forces lots of energy needed to break the bonds water has a high melting and boiling points when water boils a hydrogen bonds are broken completely
