C5-C7 BONDING Flashcards
Bond
An attraction between two atoms that holds them together
Ion
An atom that has gained a charge by gaining or losing electrons
Charge
Whether an ion is positive or negative
Cation
Positive ion formed by losing electrons , formed by metal atoms
Anion
Negative ion formed by gaining electrons. Formed by non-metal atoms
Size of charge
The number of electrons transferred affects the size of charge : losing two electrons makes a 2+ charge, gaining three electrons makes a 3- charge
How many electrons are gained or lost
Metals: however many electrons are in the outer shell
Non-metals: however many electrons are needed to fill the outer shell
Electrostatic force
A force attraction between a positive and negative particle
Ionic pound
When two oppositely charge ions are held together by an electrostatic force
Forming ionic bonds
Electrons are transferred form a metal atom to a non-metal atom to form a positive metal cation and a negative metal anion the oppositely charged ions are attracted to each other
Chemical formula
Shows the number of atoms of each element present in one unit of a compound
Writing formulae
Each chemical symbol starts with a capital letter
The number of each atom present is shown with a subscript number after the symbol
Determining ionic formulae
Ensure the total number of positive and negative chargers balance
Change the number of each ion present by changing the subscript numbers
Compound ions
An ion made from two or more atoms that share a charge
Common compound ions
Hydroxide: OH- Nitrate: NO3 Sulfate: SO42- Sulfite : SO32- Carbonate : CO32- Ammonium: NH4+
Including compound ions in formulae
If you need more than one, put brackets around it
E.g. MG(OH)2
Ionic lattice
The structure of ionic compounds: a repeating 3D pattern of alternating positive and negative ions
Crystal
A piece of material with a regular shape and straight edges formed by the regular pattern of ions in an ionic lattice
Melting point of ionic compounds
High because melting needs a lot of energy to break strong ionic bonds
Solubility of ionic compounds
Many ionic compounds dissolve in water
Electrical conductivity of ionic compounds
Solid: do not conduct because ions can’t move
Liquid (molten or solution): do conduct because ions can move
How ionic compounds conduct electricity
When they are in a liquid form the positive cations move to the negative electrode (cathode) and the negative anions move the positive electrode (anode)
Covent bond
An electrostatic attraction between two atoms and a share pair of electrons
Double bond
A covalent bond involving two shared pairs of electrons
Dots and crops diagrams
A bonding diagram showing the electrons in the outer shell of each atom with electrons drawn as dots and crosses
Hydrogen H2
Two overlapping circles both labelled H one pair in the over lap
Hydrogen chloride HCL
Two overlapping circles labelled H and CL one pair in the overlap , 6 electrons around CL
Oxygen O2
Two overlapping circles both labelled O two pairs in the overlap 4 electrons around each O
Water H2O
Three overlapping circles in a line labelled H, O, H. A pair in each overlap 4 electrons around O
Carbon dioxide, CO2
Three overlapping circles in a line labelled O,C,O two pairs in each over lap 4 electrons around each O
Methane CH4
Five circles with one in the centre labelled C and 4 labelled H around it a pair in each overlap
Valency
The number of covalent bonds an atom can form
Valency and groups
Group4=4 (4 electrons needed)
Group5=3 (3 electrons needed)
Group6=2 (2 electrons needed)
Group7=1 (1 electrons needed)
Working out molecular formulae
Find the lowest common multiple of the valency of each atom use the number of an atom required to reach the LCM
Molecule
A particle made from two or more atoms bonded together
Simple molecular structure
A structure made of small molecules in which a few atoms join together to form a small particle
Structure of molecular substances
Atoms in a molecule are held together by strong covalent bonds. Neighbouring molecules are held close by weak intermolecular forces
Intermolecular force
A weak electrostatic force that holds two neighbouring molecules together
Melting point of simple molecular compounds
Low because melting only needs a little energy to break weak intermolecular forces
Electrical conductivity of simple molecular compounds
Do not conduct because there are no electrons that are free to move
Examples of simple molecular substances
Hydrogen gas, oxygen gas, water, carbon dioxide, methane
Giant molecular structure
A structure made of a reappearing patterned of atoms covalently bonded together
Melting point of giant molecular compounds
High because melting requires breaking strong covalent bonds
Electrical conductivity of simple molecular compounds
Do not conduct (except graphite) because there are no electrons free to move
Examples of simple molecular substances
Silicon dioxide (silica), diamond, graphite
Polymer
A large molecule made of a small unit repeated many times
Monomer
A small molecule that can be joined together many times to form a polymer
Allotrope
A different structural form of an element made of the same atoms just bonded together differently
Carbons allotrope
Graphite, diamond, graphene, fullerenes
Graphite
Structure: stacked sheets of carbon in a honeycomb pattern with delocalised electrons between them
Properties: sheets slide apart easily, excellent conductor
Uses: lubricants
Diamond
Structure: repeating pattern of 4 atoms bonded to 4 others
Properties: very strong, excellent conductor
Uses: none yet, but potentially many
Graphene
Structure: a single layer of atoms in a honeycomb pattern
Properties: very strong , excellent conductor
Uses: none yet but potentially many
Buckminster fullerene
Structure: ball-shaped molecules of C60
Properties: low melting point
Uses: none
Carbon nanotubes
Structure: cylinders made of carbon bonded in a honey comb pattern
Properties: very strong excellent conductors
Uses:strong and felixaeble materials, electronics
Structure of metals
A lattice of positive metals ions surrounded by a cloud of delocalised electrons
Delocalised electrons
Electrons that are not bound to a single atom but more freely around many
Metallic bonding
The electrostatic attraction between the lattice of positive metal ions and the cloud of delocalised electrons
Electrical conductivity of metals
Metals are good conductors because the electrons are free to move
Comparing the conductivity of metals
Metals with more electrons in the outer shell such as AL are better conductors than those with fewer such as LI because there are more delocalised electrons that are able to move
Malleable
When a substance dents when it is hit instead of shattering
Malleability of metals
Metals are malleable because the atoms are arranged in regular sheets and these sheets can easily slide over each other when hit
Melting point of metals
High because melting them requires breaking the strong force of attraction between the cloud of delocalised electrons
Classifying materials
The properties of a material can be used to determine the type of bonding in it
Properties of ionic compounds
High melting point, does not conduct electricity, sometimes soluble in water
Properties of giant molecular compounds
High melting point, does not conduct electricity (except graphite) insoluble in water
Properties of metallic compounds
High melting point , does not conduct electricity, insoluble in water
Bonding models
The ideas and drawings that we use to explain the bonding of atoms
Problems with bonding models
Dot and cross diagrams make electrons seem different, they are not
Atoms appear stationary the are actually vibrating
Atoms don’t appear to be touching when they actually are
