Bonding, structure and properties Flashcards
What are molecules usually made from?
non-metal atoms
When does a covalent molecular bond form?
When two non-metal atoms share their unpaired outer (valence) electrons by overlapping their electron clouds a covalent bond forms. The attraction of the two positive nuclei for the pair of shared electrons holds the atoms together. If there are a limited number of atoms in the structure it is known as a covalent molecule.
When does a covalent bond occur?
When two or more non-metal atoms share their unpaired outer electrons (valence).
What is a diatomic molecule
a molecule that contains only two atoms
What are the diatomic elements?
I2 H2 N2 Br2 O2 Cl2 F2
Draw and label the shapes used to draw a chemical showing its 3 dimensional figure
A triangle should represent A bong coming out of the page (towards you)
A dotted line should represent a bond going into the page (away from you)
A straight line should represent a bong in the same place as the page
What are the covalent network elements and compounds?
Carbon silicon Boron Silicon dioxide Silicon carbide
What is the attraction between charged particles called?
Electrostatic attraction
What are ionic bonds?
Ionic bonds are the electrostatic forces of attraction between positive ions and negative ions
When does ionic bonding occur?
Occurs when a metal atom transfers its unpaired outer electrons to a non-metal atom and this forms a positive metal Ion and a negative non-metal ion. The ions attract each other in all directions and a giant ionic lattice forms
Describe the structure of ionic compounds
they have what is known as lattice structure, this is a regular arrangement of positive and negative ions
When does a covalent network bond form?
When tow non-metal atoms share their unpaired outer (valence) electrons by overlapping their electron clouds a covalent bond forms. The attraction of the two positive nuclei for the pair of shared electrons holds the atoms together. If there are an unlimited number of atoms in the structure it is known as a covalent network.
What is the melting point of a covalent network?
they have very high melting points, as strong covalent bonds are being broken
Do covalent networks conduct electricity?
They do not conduct in any state, except graphite which has delocalised electrons
When are covalent networks soluble?
they are insoluble in any solvent
What are the five main covalent networks?
carbon
silicon
boron
silicon dioxide
silicon carbide
how many atoms are in a covalent network?
unlimited number of atoms in the network
Describe the melting points of ionic lattices?
they have high melitng points as strong ionic bonds are being broken
all ionic lattices are solid at room temperature
When do ionic lattices conduct eletcticity?
not in solids
yes as melts or solutions as their ions are then free to move
When are ionic lattices soluble?
tend to be soluble in water reather than non-aqueaous solvents but can vary
How many atoms are in covalent molecular?
fixed number of atoms in their molecules
when do covalent molecular molecules conduct electricity?
low as weak forces of attraction being broken
Describe the melting points of covalent molecular molecules
not in any state
When are covalent moleculear molecules soluble
tend to be more in non aqueous solvents than water but this can vary
Describe a tetrahedral shape such as methane
four hydrogen atoms symmetrically arranged around a central carbon atom, forming 109.5° bond angles.
Describe a trigonal pyrimidial shape
It has three bonded atoms and one lone pair on the central atom which creates a three-sided pyramid with bond angles of about 107°
Describe an angular shape
when a central atom has two bonded atoms and two lone pairs. The bond angle is about 104.5°, and the lone pairs push the bonded atoms closer together, creating a bent shape.
Describe a linear shape
a central atom bonded to two atoms with bond angles of 180°. The atoms are arranged in a straight line, with no lone pairs on the central atom
