chemistry - atomic structure, the periodic table and states of matter

what is an atom

an atom is the smallest unit, smallest part of an element and the building block of all matter

what are the sub-atomic particles of atoms, including positions, relative charge and mass

protons:

• found in the nucleus

• relative charge = 1

• relative mass = 1

neutrons:

• found in the nucleus

• relative charge = o

• relative mass = 1

electrons:

• orbit the nucleus in shells

• relative charge = -1

• relative mass = 0 (1/2000)

what is atomic number?

the number of protons in an atom, which determine the atoms identity

what is mass number

the number of protons + the number of neutrons

what are isotopes?

variants of the smae element with different amounts of neutrons

what is relative atomic mass?

the weighted average of the isotopes of an element compared to carbon 12

how to calculate relative atomic mass?

(percentage abundance of each isotope x the mass number), add all of them together and divide by 100

the periodic table

how are elements arranged in the periodic table?

• in order of increasing atomic number

• in groups (columns) and periods (rows)

how to work out the electronic configuration of an atom of an element based on its place in the periodic table?

• group number corresponds to the number of electrons in the atoms outer shell

• period number corresponds to the number of shells the atom has

use electrical conductivity to classify elements as metals/ non-metals

good conductor of electricity = metal

poor conductor of electricity = non-metal

use acid-base characteristics of oxides to classify elements as metals/ non-metals

if a elemts oxide is basic it is a metal

if it’s oxide is acidic it’s a non-metal

how is the electronic configuration of a main group element related to it’s position in the periodic table?

atomic number = number of protons = number of electrons

group number = number of electrons in the outer shell

period number = number of shell

• remember - electrons fill up the shell closest to the nucleus, which can only contain 2 electrons, before moving to the next ones, which all have a maximum of 8

why do elements in the same group have similar chemical properties?

• they have the same number of electrons in their outer shell, which are the ones involved in chemical reactions

• as they have the same number of electrons, the way they react is similar

• so they have similar chemical properties

why do the noble gases (group 0) not readily react?

because they all have full outer shells of electrons (most have 8 electrons, apart from helium which has 2)

this means they have a stable electronic configuration

so they have no tendency to lose, gain or share electrons during chemical reactions, making them mostly unreactive

states of matter

describe solids, including arrangement, movement and energy of particles

arrangement: particles are closely packed together in a regular arrangement

movement: particles vibrate in fixed places

energy: have the least amount of energy

notes: particles can’t flow or be compressed, have a fixed shape and volume

describe liquids, including arrangement, movement and energy of particles

arrangement: particles are touching, arranged randomly and fill their container

movement: particles are able to flow past eachother 

energy: liquids have more energy than solids, but less than gases as their particles can move but are still touching

notes: fixed volume but not shape, can’t be compressed, particles can flow

describe gases, including arrangement, movement and energy of particles

arrangement: particles are arranged randomly and are not touching, fill up thier container

movement: particles move rapidly in all directions, colliding with eachother and the walls of their container

energy: gas particles have the most energy as they move rapidly and are not touching

note: no fixed shape or volume, can be compressed, low density

how are interconversions between states of matter achieved?

by heating or cooling:

• solid to liquid to gas = adding heat

• gas to liquid to solid = removing heat

solids have the strongest forces of attractions between the particles (they cannot move), while gases have the weakest force of attraction between the particles (they aren’t touching)

adding heat helps to change the state of matter as it adds energy to help break the bonds holding the particles together, so they are able to move more

what are the interconversions between states of matter when going from solid to gas?

solid to liquid = melting

liquid to gas = evaporating

solid to gas = sublimation

as you add heat, the particles gain kinetic energy and move more, and further apart

what are the interconversions between states of matter when going from gas to solid

gas to liquid = condensing

liquid to solid = freezing

gas to solid = deposition

as you remove heat, the particles lose kinetic energy and move less, instead moving closer together

changes in arrangement, movement and energy of particles during changes of state

change in arrangement:

• solid to liquid to gas = particles spread apart and are arranged more randomly

• gas to liquid to solid = particles move closer together and become more regularly arranged

change in energy:

• solid to liquid to gas = particles gain kinetic energy and the bonds between particles become weaker

• gas to liquid to solid = particles lose kinetic energy and the bonds between particles become stronger

change in movement:

• solid to liquid to gas = particles move faster and more randomly away frome eachother

• gas to liquid to solid = particles move less and are less able to move past eachother