1-Atomic structure and the periodic table

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atoms are made up of:
neutrons- relative mass of 1, charge of 0
protons- relative mass of 1, charge of +1
electrons- relative mass of 0, charge of -1
charge of atoms and ions
overall, an atom is neutral as the positive and negative charges balance out
an ion is an atom with a charge and can happen when electrons are lost or gained
protons determine what element an atom is
isotopes are different forms of the same element with the same number of protons but different number of neutrons
relative atomic mass from isotopic abundance
is sum of (isotope abundance x isotope mass) ÷ sum of abundance of all isotopes
top number on symbol- relative atomic mass = total number of protons + neutrons
bottom number on symbol- atomic number = number of protons
the number of protons is always equal to the number of electrons in an atom (NOT Ion)
molecules- group of two or more atoms chemically bonded together which can be the same or different elements
compounds- group of two or more atoms chemically bonded together which are different elements
mixtures- two or more substances that are not chemically bonded together
terminology
a mixture is a liquid and an insoluble solid
a solution is a liquid and a soluble solid
a solute is the substance dissolved in a solvent
a solvent is a liquid that dissolves the solute
filtration
separates insoluble solids from liquids
place filter paper in a funnel and pour solution on it, only the liquid will pass through
evaporation
separates soluble solid from a liquid
place solution in evaporating dish, slowly heat with a Bunsen burner, the solvent will start evaporating, crystals will start to form as it will be concentrated and eventually just leave dry crystals of the solid
quick and easy method but can't be used for everything as some solids can decompose when heated
crystallisation
separates soluble solid from a liquid
place solution in evaporating dish and heat gently with a water bath, when crystals start to form stop heating it and leave it to cool, filter the solution so you are left with the crystals, leave them overnight to dry
slower technique
used for solids susceptible to thermal decomposition
simple distillation
separates a liquid from a solution
flask with solution is sealed with a bung so that no gas can escape, thermometer is put through the bung, Bunsen burner used to heat solution in flask, flask is linked to condenser with beaker at the end to capture the pure separated liquid
a condenser is surrounded by a water jacket which has a continual stream of cold water flowing through it from the bottom to the top
fractional distillation
separates liquid from a mixture of liquids
flask has a fractionating column above it where liquid with lowest boiling point rises when evaporated, passes into the condenser where it condenses into a liquid and is collected in the beaker, this is repeated with the other liquids
the glass rods in the fractionating column would condense the other liquids with a higher boiling point so that they don't rise into the condenser
history of the atom
Democritus- everything made from tiny particles, can't be broken down, separated by empty space
Dalton- solid spheres, diff types make up diff elements
Thompson- plum pudding- ball of positive charge with electrons scattered around
Rutherford- alpha scattering exp- nuclear model- positive charge nucleus, negative charge cloud around it
Bohr- electrons orbit nucleus in shells
Rutherford- protons
Chadwick- neutrons
arrangement of electrons in atoms:
orbit the nucleus in shells, 1st can hold 2, rest can hold 8
if they have an incomplete outer shell of electrons then they are unstable
gaining electrons causes the atom to become -
losing electrons causes the atom to become +
elements in the same groups have similar chemical properties due to having the same number of electrons in their outer shells
element's group number is the number of electrons in their outer shells
structure of the periodic table
each row is called a period - same number of shells
each column is called a group
metals:
have strong metallic bonds
are malleable, good conductors of heat, have high melting and boiling points, shiny, sonorous
most elements are metals - found on left of periodic table
form positive ions when they react
usually become more reactive towards the bottom of the column as they have lots of shells and far from nucleus so it cant hold on to them so strongly, they will be lost more easily
non-metals:
are brittle, usually poor conductors of electricity, have low melting and boiling points, are dull in colour
they have lower densities than metals
transition metals:
are in the middle of the periodic table
have properties of typical metals and extra
they can form more than one ion
they are good catalysts
group 1 - alkali metals
they are soft, have low density, have low melting points, they are reactive
as you go down the group they become more reactive and their melting and boiling points decrease
water- reacts vigorously, forms metal hydroxide + hydrogen gas
chlorine gas- reacts vigorously, form white metal chloride salts
oxygen- form metal oxides
group 7 - halogens
as you go down they become less reactive and their melting and boiling points increase, they are poisonous
F is a yellow gas and very reactive, Cl is a green gas and less reactive, Br is a brown liquid, I is a dark grey solid
they come in pairs (diatomic) with covalent bond
they can form covalent bonds with other non-metals
they can form ionic bonds with metals
more reactive halogens will always displace less reactive ones
group 0 - noble gases
as you go down, their boiling point increases
they are colourless gases
they are non-flammable
they are unreactive (inert) due to their full outer shells
they exist as single atoms
balancing equations
big numbers that are in front of an element times the whole molecule
little numbers (subscripts) that are behind an element times just the element it's behind