Bonding and structures Flashcards
What is the definition of ionic bonding ?
. It occurs between a metal and a non-metal and is the transfer of electrons to achieve a full outer shell.
. Oppositely charged ions attract through electrostatic forces to form a giant ionic lattice.
E.g sodium chloride
What is an ion ?
Charged particles caused by electron transfer.
What are the 5 common compound ions ?
. Sulfate- SO4,2- . Hydroxide- OH- . Nitrate- NO3,- . Carbonate- CO3,2- . Ammonium- NH4,+
What is the definition of covalent bonding ?
. Occurs between 2 non-metals and electrons are shared between the two outer shells in order to achieve a full outer shell.
. The shared electrons can be represented using dot and cross diagrams.
What is the definition of dative covalent bonding ?
. When both the electrons in the shared pair are supplied from only one atom, which has a free unreacted lone pair.
. The bond is shown by an arrow.
What is the definition of metallic bonding ?
. Consists of a lattice of positively charged ions surrounded by a sea of delocalised electrons.
. There is a very strong electrostatic force of attraction between these oppositely charged particles.
How does metallic bonding increase its sting attraction ?
The greater the charge of the positive ion, the stronger the attractive force as more electrons are released into the sea.
What are the properties of ionic crystal structures ?
. High melting point and boiling points because of the strong electrostatic forces holding the ionic lattice together so require lots of energy to overcome.
. They are also very brittle.
Why can ionic crystal structures conduct electricity when molten ?
The ions separate and are no longer held in a lattice so are free to move end carry a flow of charge- an electrical current.
What are the properties of metallic crystal structures ?
. Good conductors due to their sea of delocalised electrons being able to freely move and carry a flow of charge.
. Are malleable as the layers of positive ions are able to slide over each other.
. Have high melting points because of the strong electrostatic forces of attraction between positive ions and delocalised electrons so need more energy to overcome.
What are the properties of simple molecular crystals ?
. Consists of covalently bonded molecules held together by weak van der waals forces.
. Have low melting and boiling points because of the weak van der waals forces so not much energy is required to overcome them.
. They are poor conductors as they do not contain and charged particles.
What are the properties of macromolecules crystals/ structures ?
. Are covalently bonded into a giant lattice structure.
. Has a very high melting point because each atom can from multiple covalent binds which are very strong.
. Are rigid due to its strong covalent lattice.
. E.g- diamond is made of carbon atoms that can form 4 covalent bonds each so is very strong.
. E.g- graphite made of carbon atoms that can form 3 covalent bonds in flat sheets. Has delocalised electrons so can conduct electricity.
What are lone pairs ?
. Unreacted pair of electrons around the central atom which provide additional repulsive forces.
How do lone pairs affect bond angels ?
For every lone pair present, the bond angel between covalent bonds is reduced by 2.5 degrees.
What is the name of the bond shape and bond angle for a molecule with 0 lone pairs and 2 reacting pairs ?
. 180 degrees
. Linear
What is the bond name and bond angle of a molecule with 1 lone pair and 3 reacting pairs ?
. 120 degrees
. Bent
What is the bond name and bond angle of a molecule with 0 lone pairs and 3 reacting pairs ?
. 120 degrees
. Trigonal Planar
What is the bond name and bond angle of a molecule with 0 lone pairs and 4 reacting pairs ?
. 109 degrees
. Tetrahedral
What is the bond name and bond angle of a molecule with 1 lone pairs and 4 reacting pairs ?
. 109 degrees
. Trigonal Pyramidal
What is the bond name and bond angle of a molecule with 0 lone pairs and 5 reacting pairs ?
. 120/ 90 degrees
. Trigonal Bipyramidal
What is the bond name and bond angle of a molecule with 0 lone pairs and 6 reacting pairs ?
. 90 degrees
. Octahedral
What is the definition of electronegativity ?
The power of an atom to attract negative charge towards itself within a covalent bond.
What is the trend in electronegativity ?
. Increases along a period as atomic radius decreases.
. Decreases down a group as shielding increases.
How does a polar bond form ?
. If the two atoms that are bonded have different electronegativities.
How does a permanent dipole bond arise ?
. A polar bond is formed by the difference in electronegativies between the bonded atoms as the more electronegative atom draws in more of the negative charge, creating a region of delta negative and delta positive.
. Can align to form a lattice of molecules.
How does an induced dipole bond arise ?
When the electrons orbit around a molecule which are influenced by another charged particle
Explain Van Der Waals forces ?
. The weakest intermolecular force and it acts as an induced dipole between molecules.
. It can be strengthened depending on the Mr of the molecule, the larger the Mr the stronger the van der waals forces.
Explain hydrogen bonding ?
. It is the strongest intermolecular force and only form between hydrogen and 3 more electronegative atoms, N, O and F.
. Hydrogen bonds are shown by a dotted line.
. Have a higher melting and boiling points.
