Chemistry Paper 1

What are the relative charges of protons, nuetrons and electrons?

p:+1 n:0 e: -1

what are the relative masses of the 3 subatomic particles?

p:1 n:1 e:1/1836

where are the subatomic particles located?

p: in nucleus n: in nucleus e: in shells around nucleus

what is the atomic number?

the number of protons in an atoms nucleus

what is the mass number?

the total number of protons and neutrons

how do you calculate the number of neutrons?

mass number-atomic number

why has an atomic got a neutral charge?

it has equal number of protons and electrons

what is an isotope?

an atom of the same element with the same number of protons but a different number of neutrons

why do isotopes have the same chemical properties?

they have the same electron arrangement in the shells

how do you calculate relative atomic mass from isotopes?

(isotope 1 x it's abundance) + (isotope 2 x it’s abundance) / 100

what is an ion?

a charged particle formed when an atom/group of atoms gains or loses an electron

what is the difference between an atom and an ion?

an atom is neutral and an ion has an electrical charge because electrons have been gained/lost

what is electron arrangement ( for the first 20 elements)

2,8,8,2

what was the plum pudding model?

the atom was thought to be a sphere of positive charge with negative electrons embedded in it

what did the alpha scattering experiment reveal?

that the atom is mostly space with a tiny, dense, positively charged nucleus

how was the periodic table originally arranged and how is it arranged today?

mendeleev mainly used atomic weight and properties to arrange the elements. today it's arranged by increasing atomic number

what did mendeleev contribute to the periodic table?

he left gaps for undiscovered elements and predicted their properties

what does the group number tell you?

groups 1-7: the number of outer shell electrons. group 0: has full outer shell

what does the period number tell you?

the number of shells

why do elements of the same group have similar properties?

they have the same number of outer shell electrons

why are noble gases unreactive?

they have full outer shells, making them stable

how does group 1 reactivity change down the group? and why?

it increases because the outer electron is further from the nucleus and more shielded, so the attraction is weaker and the electron is lost more easily

what happens when group 1 metals react with water?

they form a metal hydroxide and hydrogen

how do reactions change down group 1

reactions become more vigorous and melting points decrease

how does reactivity change down group 7?

it decreases

what are the names of group 1, group 7 and group 0

1- alkali metals

7- the halogens

0- noble gases

why does halogen reactivity decrease down the group?

there are more shells, therefore greater sheilding, so the nucleus attracts an incoming nucleus less strongly

what is a displacement reaction?

a more reactive element displaces a less reactive element in a reaction

what is ionic bonding?

the electrostatic attraction between oppositely charged ions

how is an ionic bond formed?

electrons transfer from a metal atom between a non metal atom, forming oppositely charged ions

what is an ionic lattice?

a giant, regular arrangement of oppositely charged ions

is the melting point of a ionic compound high or low and why

high- strong electrostatic attractions between oppositely charged ions require a lot of energy to overcome

why can’t solid ionic compounds conduct electricity

their ions are fixed in place and cant move

what must ionic compounds be to conduct electricity

molten or dissolved

why are ionic compounds brittle

when layers shift, ions with the same charge line up and repel, causing the structure to break

what is covalent bonding?

the strong electrostatic attraction between a shared pair of electrons and the nuclei of the bonded atoms

which types of atoms are involved in covalent bonds

non metal atoms

what is a simple molecular substance

a substance made up of small molecules containing atoms joined by covelent bonds

why do simple molecular substances have low melting and boiling points?

weak forces between molecules require little energy to overcome

why do simple molecular substances not conduct electricity,

they have no free ions or delocalised electrons to carry charge

why can a substance with strong covalent bonds still have a low boiling point?

the intermolecular forces determine the melting point, not the covalent bonds

what is a giant covalent structure

a large network of atoms joined by many strong covelent bonds

why do giant covelent structures have high melting points

many strong covalent bonds must be broken , requiring a lot of energy

why is diamond very hard

each carbon atom is strongly bonded to four others in a 3 dimensional structure

does diamond conduct electricity and why

no- all it’s outer shell electrons are used in covalent bonds, leaving no delocalised electrons to carry charge

can graphite conduct electricity and why

yes- each carbon atom has one delocalised electron that can move through the structure

why is graphite soft and slippery

it’s layers can slide over eachother because the forces in the layers are weak

what is kind of structure is silicon dioxide

a giant covalent structure

is silicons dioxides melting point high or low and why

high- contains lots of strong covalent bonds that require a lot of energy to overcome

what is metallic bonding?

the electrostatic attraction between positive metal ions and delocalised electrons

why can metals conduct electricity

delocalised electrons move through the structure and carry charge

why can metals conduct thermal energy

delocalised electrons transfer energy through the structure

why do metals often have high melting points

strong attractions between positive metal ions and delocalised electrons require lots of energy to overcome

why are metals malleable

layers of metal ions can slide past each other while the metallic bonding remains

what is an alloy

a mixture of a metal with one or more other elements

why are alloys usually harder than pure metals

different sizes atoms distort the regular layers , making it harder for them to slide over eachother

why are pure metals often malleable

their regular layers of atoms can slide over eachother

what is the difference between a pure metal and a alloy

a pure metals contains one element; an alloy contains a metal mixed with other element(s)

what happens to particles when a solid melts

they gain energy and can move past eachother instead of vibrating in fixed positions

what happens to particles when a liquid boils

particles gain enough energy to overcome the attractions holding them close and move far apart

what is sublimation

a change directly from a solid to a gas

what is internal energy

the total kinetic and potential energy of particles in a system

what happens to temperature during a change of state

it stays constant while energy is used to change the arrangement, and seperate particles

what is a polymer

a large molecule made from many repeating units called monomers

why can polymers have different properties

their molecular structures and the forces between their chains differ

a substance has a high melting point and conducts electricity when molten . what is it

an ionic lattice because the ions are fixed when solid but mobile when molten

a substance has a low melting point and does not conduct electricity. what is it

a simple molecular structure because they have weak forces between molecules and no mobile charged particles

why does graphite conduct electricity but diamond does not

graphite has delocalised electrons, diamond uses all its outer electrons in covalent bonds

a metal is mixed with another element and becomes harder , why?

the different sized atoms disrupt the regular layers , making it harder for them to slide

formula for density

mass over dxv