atomic structure and fundamental/basic ideas

chemistry aqa gcse

What is the electrical charge of an electron?

-1

What is the relative mass of an electron?

1/1836

What is the electrical charge of a proton?

+1

What is the relative mass of a proton?

1

What is the electrical charge of a neutron?

0

What is the relative mass of a neutron?

1

what is the radius of an atom

0.1nm

What is the overall charge of an atom?

0

How do you find the number of protons and electrons in an atom?

Atomic number = protons = electrons

What is an ion?

An atom or group of atoms that has lost or gained electrons, and so has either a negative or positive charge

What is the electrical configuration of an atom?

A diagram or number (e.g. 2.8.1) showing the number of shells and electrons in those shells of an atom

What are the rules of electron shells?

First shell can have up to 2 atoms, rest can have up to 8, if outer shell is not full this is what makes an atom react (so the shell can be filled)

How do you find the electrical configuration of an atom?

By using the atomic number (no. of electrons) to figure out how many electrons must be in each shell. E.g. 20 electrons = 2.8.8.2

How do you find the electrical configuration of an atom using just the periodic table?

The periods represent the number of shells at atom has, the columns/groups represent how many electrons are in the outer shell

How do you balance a formula?

Use the valency to drop, swap and simplify - use these numbers as the little numbers after the elements/letters

What is the law of conservation of mass?

Mass cannot be created or destroyed

what is a mixture?

two or more elements or compounds not chemically combined together that can be easily separated (filtration, fractional distillation, crystallisation etc)

what is a compound?

two or more elements chemically combined together in fixed proportions

describe the plum pudding model of the atom

a ball of positive charge with electrons embedded within it

what experiment led to the nuclear model of the atom being created?

the alpha particle scattering experiment

what happened in the alpha particle scattering experiment?

most of the alpha particles directed at thin gold foil pass through but some were deflected

what did the results of the alpha particle scattering experiment show?

the mass of the atom was in the nucleus and the positive charge of the atom was in the nucleus, suggested that the electrons orbited the nucleus

describe the Bohr model of the atom

electrons orbitted the nucleus at specific distance (on energy levels/shells), positive charge within nucleus

compare the plum pudding model and the nuclear model of the atom (6)

the plum pudding model was one sphere of positive charge, whereas the nuclear model was separated into the nucleus and surrounding electrons with positive charge concentrated in the nucleus. the plum pudding model had electrons embedded within, nuclear model has them on the outside. the mass of the nuclear model is concentrated at the centre, in the plum pudding model it is evenly distributed.

elements in the same group have the same…

number of electrons in their outer shell

groups are…

COLUMNS

elements in the same period have the same…

number of shells

how were elements arranged before the discovery of protons, neutrons and electrons?

by atomic weights

how are elements in the periodic table arranged?

by atomic (proton) number

why did Mendeleev leave gaps in his periodic table?

for undiscovered elements

elements that react to form positive ions are…

metals

elements that react to form negative ions are…

non-metals

what are the elements in group 0 called?

noble gases

why are the noble gases unreactive?

they have a full outer shell so don’t react to lose/gain electrons

what happens to the boiling points of noble gases as you go down the group?

increase

what are the elements in group 1 known as?

alkali metals

why are the alkali metals very reactive?

they only have 1 electron in their outer shell

what are the general properties of alkali metals?

soft, reactive, have a low density

what happens to boiling points of alkali metals as you go down the group?

decreases

what happens to the reactivity of alkali metals as you go down the group and why?

they get more reactive as the outer shell electron is further away from the nucleus and the attraction is weaker, therefore it is more easily lost

what happens when alkali metals react with water?

react vigorously and produce hydrogen gas and metal hydroxides, more violent reactions and more energy released as you go down the group

what happens when alkali metals react with chlorine?

when heated in chlorine gas, alkali metals form white metal chloride salts

what happens when alkali metals react with oxygen?

form a metal oxide, lithium forms lithium oxide, sodium forms a mixture of sodium oxide and sodium peroxide, potassium forms a mixture of potassium peroxide and potassium superoxide

how are alkali metals different to transition metals?

more reactive, less dense, strong and hard, have lower melting points

is making bonds exothermic or endothermic?

exothermic

is breaking bonds exothermic or endothermic?

endothermic

what are the group 7 elements called?

halogens

describe fluorine

yellow, poisonous, very reactive gas

describe chlorine

dense, green, poisonous, fairly reactive gas

describe bromine

dense, poisonous, volatile, red-brown liquid

describe iodine

dark grey crystalline solid or poisonous purple vapour

what happens to the reactivity of halogens as you go down the group and why?

decreases as it’s harder to gain an extra electron as the outer shell is further from the nucleus and attraction forces are weaker

what happens to the boiling points of halogens as you go down the group?

increases

why are all halogens reactive?

they have 7 electrons in their outer shell

what happens when a halogen reacts with a less reactive halogen?

the first halogen will displace the second from the aqeuous solution of its salt