Key concepts Flashcards
how are ions formed?
when atoms gain or lose electrons
what is the plum pudding model?
that an atom was positively charged and contained negatively charged electrons
how was the plum pudding model wrong?
because alpha particles passed straight through, deflected more than expected or even deflected backwards
what is the nuclear atom?
an atom has a positive nucleus surrounded by negative electrons with empty space
what is the bohr model?
shows that electrons can only exist in a fixed shell orbit with fixed energy
what charge are protons?
positive
what charge are neutrons?
neutral
what charge are electrons?
negative
what is the mass of a proton?
1
what is the mass of a neutron?
1
what is the mass of a electron?
negligible
what charge does a nucleus have?
positive
what does the nucleus contain?
protons and neutrons
what charge to atoms have?
neutral - no charge
why does an atom have no charge?
because they have the same number of protons as electrons
why do ions have a charge?
because there isn’t the same number of protons and electrons
what does the atomic number tell you?
how many protons an atom has
what does the mass number tell you?
the total number of protons and neutrons
which is bigger the mass or atomic number?
the mass number
what are isotopes?
different forms of elements with the same number of protons and a different number of neutrons
what is the relationship with the atomic and mass number of isotopes?
they have the same atomic number but different mass numbers
what is relative atomic mass?
the average mass of one atom of the element compared to 1/12 of the mass of one atom of carbon12
what happens if an element has one isotope?
it’s relative atomic mass with be the same as its mass number
how to work out relative atomic mass from isotopic abundances
multiply each relative isotopic mass but it’s abundance and add up results
divide by the sum of abundances
how did Mendeleev sort the elements originally?
through their properties
what did he realise by doing this?
by putting the elements in order of atomic mass he could put the elements with similar chemical properties in columns
How did Mendeleev fill in the gaps?
used properties of other elements in the columns to predict undiscovered elements properties
what do groups show?
the number of electrons it has on its outer shell
what do periods show?
how many full shells an element has
how do negative ions form?
when atoms gain electrons
do negative ions have more or less electrons than protons?
more
how are positive ions formed?
when an atom loses electrons
does a positive ion have more or less electrons than protons?
less
what links electrons and charge?
the number of electrons lost or gained is the charge number
what are ionic compounds made of?
a positively charged part and a negatively charged part
what is the overall charge of an ionic compound?
zero
what does it mean if an ion ends in ‘ate’?
they are negative ions containing oxygen and one other element
what does it mean if an ion ends in ‘ide’?
negative ions containing only one element
which ion is an acceptable to the rule when an ion ends in ‘ide’?
hydroxide ions as they are OH minus
How is an ionic bond formed?
when a metal and non metal react together
does a metal lose or gain electrons and what does it form?
loses electrons to form positive ion
does a non metal gain or lose electrons and what does it form?
gains electrons to form a negative ion
what is the structure of ionic compounds?
giant ionic lattice structures
properties of ionic compounds
strong electrostatic forces
high m and b points
don’t conduct if a solid
dissolve in water
why does an ionic compound carry a current when a liquid or gas?
because the ions are free to move
how are covalent bonds formed?
when two non metals share electrons between atoms
What substance has covalent bonds?
simple molecular substances
simple molecular substances properties
very strong covalent bonds weak intermolecular forces low m and b points don’t conduct some soluble some aren’t
why do simple molecular substances not conduct?
because they don’t contain any free electrons
what state of matter are molecular substances at room temp?
gas or liquid
how do melting and boiling points increase?
if the molecule gets bigger, the strength of intermolecular forces increase so more energy is needed to break them
what are polymers?
molecules made up of long chains of covalently bonded carbon atoms
how do polymers form?
when lots of small monomers join together
Giant covalent structure properties
strong covalent bonds
high m and b points
don’t conduct
aren’t soluble
why don’t giant covalent structures conduct?
because they don’t contain any charged particles
Diamonds properties
has 4 covalent bonds high m and b point strong covalent bonds hard structure no delocalised electrons
Graphite properties
forms three covalent bonds
high melting and boiling point
has one delocalised electron
conducts electricity
why is graphite a good lubricant?
because it’s layers can slide over each other as there are no covalent bonds between layers
Fullerene properties
shaped like hollow balls or closed tubes
carbon atoms in shape of hexagon
huge surface area
conduct electricity
what are fullerenes used for?
drug delivery
why is it good that fullerenes have a large surface area?
help make great industrial catalysts
how are metallic bonds formed?
when two metals react together
Metallic bond properties
electrostatic forces very strong high m and b points aren’t soluble can conduct delocalised electrons
why are metals more dense?
the ions are packed closer together
how are metals malleable?
layers can slide over each other
properties of non metals
dull more brittle low density don’t conduct low m and b points gain electrons for full outer shell
