2-bonding structure and properties of matter Flashcards
how are ions formed when electrons are transferred
when atoms lose or gain electrons to form ions, theyre trying to get a full outer shell like a noble gas (stable electronic structure) as atoms with full outer shells are stable
when metals form ions they lose electrons from their outer shell to form positive ions
when non metals form ions they gain electrons into their outer shell to form negative ions
the number of electrons lost or gained is the same as the charge of the ions
(if 2 electrons are lost = 2+)
(if 2 electrons gained = 2-)
what is an ion
a charged particle
they can be single atoms like Cl-
or a group of atoms NO3-
why are group 1 and 2
and group 6 and 7
most likely to form ions
g1 and g2 are metals and they lose electrons to form positive iosn (cations)
g6 and g7 are non metals that gain electrons to form negative iosn (anions)
group 1 form 1+ ions
group 2 forms 2+ ions
group 6 forms 2- ions
group 7 forms 1- ions
why are group 1 and 2
and group 6 and 7
most likely to form ions
g1 and g2 are metals and they lose electrons to form positive iosn (cations)
g6 and g7 are non metals that gain electrons to form negative iosn (anions)
group 1 form 1+ ions
group 2 forms 2+ ions
group 6 forms 2- ions
group 7 forms 1- ions
show the ionisation equations for
sodium
magnesium
chlorine
oxygen
1-sodium: loses 1 electron to form sodium ion with same electronic structure as neon
Na => Na+ +e-
2=magnesium: loses 2 electrons to form a magnesiumion with same electronic structure as neon
Mg => Mg2+ + 2e-
3= chlorine: gains 1 electron to form a chloride ion with same electronic structure as argon
Cl + e- => Cl-
4= oxygen: gains 2 electrons to form an oxide ion with same electronic structure as neon
O + 2e- => O2-
what is ionic bonding
when a metal and a non metal react together
the metal atom loses electrons to form a positively charged ion and the nonmetal gains these electrons to form a negatively charged ion
these oppositely charged ions are strongly attracted to one another by electrostatic forces
this attraction is called an ionic bond
what do dot and cross diagrams show
it shows the arrangement of electrons in an atom or ion
each electron is represented by a dot or cross
so these diagrams show which atom the electrons in an ion originally came from
they show how the ionic compound is formed but dont show the structure of the compound, thesize of the ions or how theyre arranged
what kind of structure do ionic compounds form
giant ionic lattice
ions form a closely packed regular lattice arrangment, theres strong electrostatic forces between oppositely charged ions in all directions in the lattice
e.g. a single crystal of sodium chloride(table salt ) is one giant ionic lattice. the Na+ & Cl- ions are held together in a regular lattice
how can giant ionic lattices be shown through diagrams
describe the 2 ways
1)model = shows relative size of ions,shows regular pattrn of ionic crystal but only shows outer layer of compound
2) ball and stick model shows regular pattern of an ionic crystal, shows how all ions are arranged, it suggests that the crystals extends beyond whats shown in the diagram
but model isnt to scale so relative sizes of ions may not be shown and in reality there are not gaps between the ions e.g. in Na+ and Cl- ions are alternate
what are all the similar properties of ionic compounds
high melting and boiling point due to many strong bonds between the ions, takes a lot if energy to overcome this attraction
when solid, the ions are held in place so compounds cant conduct electricity, when ionic compounds melt,ions are free to move so theyll carry electric current
some ionic compounds also dissolve in water, ions separate are all free to move in solution so theyll carry electric current
How to find empirical formula of an ionic compound
from the diagram of a compound
if its dot&cross= count up how many atoms there are of each element to get empirical formula
if you have 3d diagram of ionic lattice, use it to work out what ions are in the ionic compound
then balance charges of the ions so that overall chargge on compound is 0
e.g. a compound with potassium and oxide ions
potassium is g1 so 1+ ions
oxygen is g6 so 2- ions
potassium ion only has a 1+ charge sp you need 2 of them to balance out 2- charge of oxideion so K2O
explain how covalent bonding works
when nonmetals atoms bond together they share pairs of electrons to make covalent bonds
positively charged nuclei of bonded atoms are attracted to the shared pair of electrons by electrostatc forces making covalent bonds very strong
atoms only share electrons in their outer shells(energy level)
each single covalent bond provides one extra shared electron for each atom
each atom involved generally makes enough covalent bonds to fill up its outer shell. full outer shell gives them the electronic structure of a noble gas=stable
covalent bonding happens in compounds of non metals (H2O) and in non metal elements (Cl2)
how can you show covalent bonding with dot and cross diagram
dot and cross diagram =overlap between outer orbitals of 2 atoms are shared between those atoms
they are useful for showing which atoms the electrons in a covalent bond come from
but they dont show the relative sizes of the atoms or how the atoms are arranged in space
vhow can you show covalent bonding with the displayed formula
shows covalent bonds as single lines between atoms
its good for showing how atoms are connected in large molecules
but they dont show 3D structure of molecule or which atoms the electrons in the covalent bond have come from
how can you show covalent bonding with 3D model
it shows atoms, covalent bonds, arrangement in space next to each other
but 3D models can quickly get confusing for large molecules where there are lots of atoms to include
they dont show where the electrons in the bonds have come from either
how can you find the molecular formula of a simple molecular compound from any of the 3 diagrams
count up how many atoms of each element there are
H H
| |
e.g. H -C-C- H
| |
H H
so it is C2H6
what are simple molecular substances and give examples
they are made up of molecules containing a few atoms joined together by covalent bonds
hydrogen - H2
has 1 electron to complete 1st shell so they form single covalent bonds with hydrogen atoms or with other elements
oxygen- O2
each oxygen atom needs 2 more electrons to complete its outer shell so in oxygen gas, 2 oxygen atoms share 2 pairs of electrons with each other making a double covalent bond
methane CH4
carbon has 4 outer electrons which is half a full shell
forms 4 covalent bonds with hydrogen atoms to fill outer shell
chlorine Cl2
each atom needs 1 more electron to complete outer shell so 2 chlroine atoms can hare 1 pair of electrons and form a single covalentbond
nitrogen N2
they need 3 more electron so 2 nitrogen atoms share 3 pairs of electrons to fill their outer shells to make triple bond
water H2O
water molecules, oxygen shares a pair of electrons with 2 H atoms to form 2 single covalent bonds
hydrogen chloride HCl
both atoms need one more electron to complete their outer shells
what are properties of simple molecular substances substances containing covalent bonds
1- atoms held together by strong covalent bonds but forces of attraction between molecules are very weak
2-to melt or boil a simple molecular compound you only need to break feeble intermolecular forces and not covalent bonds so melting and boiling point is very low because molecules are easily parted from each other
3-most are gases or liquids at room temp
4- as molecules get bigger, strength of intermolecular forces increase so more energy needed to break them and melting and boiling point increases
5-molecular compounds dont conduct electricity bc they are not charged so no free electrons or ions
what are polymers
lots of small units linked together to form a long molecule that has repeating sections
all the atoms in a polymer are joined by strong covalent bonds
how do you show polymers through diagram
draw the shortest repeating section called repeating unit
the part in the bracket is the repeating unit
‘n’ is the large number tell you the unit has repeated lots of times
bonds through the brackets join up to the next repeating unit
explain how intermolecular forces work in polymer molecules
they are larger than the ones in simple covalent molecules so more energy is needed to break them so most polymers are solid at room temperature
intermolecular forces are still weaker than ionic or covalent bonds so they generally have lower boiling points than ionic and giant molecular compounds
why are giant covalent structures macromolecules
all atoms are bonded to each other by strong covalent bonds
high melting and boiling point as lots of energy is needed to break the covalent bonds between atoms
dont contain charged particles so dont conduct electricity not even when molten (except for things like graphite)
main examples are diamond and graphite both made from carbon atoms only and silicon dioxide
why are giant covalent structures macromolecules
all atoms are bonded to each other by strong covalent bonds
high melting and boiling point as lots of energy is needed to break the covalent bonds between atoms
dont contain charged particles so dont conduct electricity not even when molten (except for things like graphite)
main examples are diamond and graphite both made from carbon atoms only and silicon dioxide
explain how diamonds are structured
each carbon atom forms 4 covalent bonds in a very rigid giant covalent structure
