UNIT 1 : Bonding Flashcards
why do atoms form bonds?
Atoms form bonds to achieve a stable electron arrangement like the Noble gases
when does a covalent bond form?
The covalent bond forms when 2 non-metal atoms share a pair of electrons
what is a molecule?
A small group of atoms held together by covalent bonds
what holds the atoms together in a covalent bond?
The forces of attraction between the positive nuclei of both atoms and the electrons in the overlap region holds the atoms together
why are covalent bonds difficult to break?
A lot of energy is required to overcome forces of attraction, covalent bonds are very strong
what are the two types of covalent bonds?
- covalent molecular substance
- covalent network substance
what are the properties of a covalent molecular substance?
- low melting and boiling points as there are weak forces of attraction between the molecules ( intermolecular forces)
- weak intermolecular forces in between molecules
- strong covalent bonds
what are properties of a covalent network substance?
- very high melting and boiling points due to strong covalent bonds
- solid at room temperature due to covalent bonds
what are examples of a covalent network substance?
- Silicon dioxide
- Diamond
what can an electron sharing diagram be used to show?
used to show the sharing of electron pairs that make up covalent bonds
what are the seven diatomic elements?
- I BRing CLay For Our New House =
iodine, bromine, chlorine, fluorine, oxygen, nitrogen, hydrogen
what are the properties of diatomic elements?
- weak intermolecular forces of attraction therefore low melting and boiling points
- held together with covalent bonds
- naturally exist as molecules with 2 atoms joined together
what are the chemical formula for diatomic elements?
- iodine = I₂
- bromine = Br₂
- chlorine = Cl₂
- flourine = F₂
- oxygen = O₂
- nitrogen = N₂
- hydrogen = H₂
what happens when hydrogen, fluorine, chlorine, bromine, iodine join together?
Form single covalent bonds
what happens when oxygen joins together?
forms a double covalent bond
what happens when nitrogen joins together?
forms a triple covalent bond
what is the difference between the chemical formula and full structural formula?
The chemical formula only tells us the number of atoms and doesn’t give us any indication about the shape
what are the different shapes of molecules?
- atoms arranged in a straight line are linear shaped
e.g hydrogen chloride H—Cl - two dimensional are angular shaped O
e.g water , H₂o / \
H H - three dimensional - trigonal pyramidal and tetrahedral
e.g nitrogen hydride
what is meant by an ion?
An ion is a positively or negatively charged element?
what is meant by an iconic bond?
An ionic bond is the electrostatic attraction between positive and negative ion
what is meant by an iconic compound?
An iconic compound is made up of both metal ions ( positively charged) and non- metals ( negatively charged) ions.
what is meant by crystal lattice?
A crystal lattice is the arrangement of ions in a solid
what charge do metal ions have?
One positive charge
what charge do non-metal ions have?
A negative charge
how do you figure out the charge of a metal ion?
it is the same as the group the element is in
how do you work out the charge of a non-metal ion?
by subtracting the group number from 8
how do u work out the charge for the nuclide notation: ions?
- positive ions have more protons than electrons
- negative ions have more electrons than protons
- the difference between protons and electrons shows the number of + or - charge
what is meant by a conductor?
Conductors are elements or compounds which allow energy to pass through
what is meant by a non-conductor?
non-conductors are elements or compounds which do not allow energy to pass
why are electrodes made of carbon?
made of carbon because carbon conducts electricity
what form of carbon is used in electrodes?
very unreactive form of graphite which also conducts electricity
what are electrodes?
The terminals through which the electrical current enters and leaves the substance under test
how do you know if an element conducts electricity?
- substance-element-metal = conducts electricity
- substance-compound-ionic-liquid solution = conducts electricity
do covalent compounds conduct electricity?
no covalent compound other than graphite conducts electricity
what are the properties of covalent compounds?
- they are made up of molecules
- do not have an overall charge
- covalent molecular substances do not conduct electricity because they do not have charged particles that are free to move
- do not conduct electricity ( except graphite)
what are ionic compounds?
compounds that contain both a metal and a non-metal element
Do ionic compounds conduct electricity when solid?
not when solid as they don’t have any free moving particles
can solid ionic compounds conduct electricity when heated or dissolved?
- when dissolved particles become free to move so they can conduct electricity
- when heated ions become free to move so they also become conducts
