Atomic structure and periodic table

Question 1

what is a molecule

Answer 1

a group or 2 or more atoms held by chemical bonds-
eg -o2 cl2 n2 c2o c2o

Question 2

what are compounds

Answer 2

substances that contain 2 or more different elements
eg- h2o,c2o,

Question 3

what is a key feature of compounds

Answer 3

they are always found in the same proportion

Question 4

what are mixtures

Answer 4

2 or more substances that are not chemically combined

• only physically mixed together

Question 5

soluble

Answer 5

dissolves in solvent

Question 6

solute

Answer 6

substance that dissolves

Question 7

solvent

Answer 7

liquid it dissolves in

Question 8

solution

Answer 8

liquid formed

Question 9

what does filtration seperate

Answer 9

insoluble solids from liquids through filter paper in filter funnel

Question 10

how do we get a dissolved soluble solid from a solution

Answer 10

evaporation or crytallisation

Question 11

explain evaporation

Answer 11

place solution in evaporating dish on tripod
slowly heat with bunsen burner
solvent evaporates and remaining solution becomes more concentrated
leaves us with dry solid crytals

Question 12

issues with evaporation

Answer 12

some solids decompose when heated(thermal decomposition)
it is broken down into something other than what we need

Question 13

explain crystallisation

Answer 13

place solution into evaporating dish
heat gently with water bath rather than bunsen burner
when some of solvent evaporates and crystals start to appear leave it to cool so more crystals form( solids are less soluble at lower temp)
filter out crystals from the remaining solutions and dry crystals by leaving it somewhere warm or warming it in an oven

Question 14

why is simple distillation used

Answer 14

to seperate liquid from solution or liquid mixture

Question 15

explain simple distillation and equipment

Answer 15

flask with bung with thermometer fit through containing solution
connected to a condenser coated by a water jacket with stream of flowing cold water(goes in through bottom and out through top)2`
at the end there is a beaker to collect the pure liquid
we need a heating device under flask like mixture

Question 16

explain simple distillation

Answer 16

heat mixture so desired liquid so it evaporates and high pressure will send it down condenser and the cold water will cool the vapour which will run down the pipe and enter beaker leaving only solute in the flask

Question 17

equipment for fractional distillation

Answer 17

flask contains solution and is heated to temp of the liquid with the lowest bp
The vapour pass through fractionating column (full of glass rods, cooler at top than bottom)
passes into condenser and condenses to liquid into the beaker.

Question 18

atomic theory

Answer 18

back in 500 bc democritus suggested everything was made of small indivisble spheres which were surrounded by empty space

Question 19

in 1800s who and what was involved in the development of atoms

Answer 19

John Dalton: described atoms as solid spheres and suggested that different types of spheres make up the different elements

Question 20

in 1897 who contributed to development of the atom and how

Answer 20

JJ thompson came up with the plum pudding model
He did experiments that proved atoms couldnt be just solid spheres and must have contained negative charged particles
His model was a ball of positive charge with discreet electrons stuck in it

Question 21

what happened in 1909 in development of the atom

Answer 21

ernest rutherford: in 1909 took + charged alpha particles and fired them at thin sheet of gold
resulted in some alpha particles reflected to side and some sent back completely- deflected
proved jj thompson theory wrong - idea that spread out positive charge wouldnt be strong enough to stop alpha particles and would be spread out

he suggested a nuclear model which said there was a compact nucleus with all positive charge and negative charge was in a cloud around central nucleus
flaw was that there was nothing stopping cloud of negative electrons rushing in to +nucleus

Question 22

what in 1913 developed atom

Answer 22

Neils bohr:in 1913 suggested that electrons orbited nucleus and were held in shells which prevents the atom from collapsing

Question 23

what did further experiments by rutherford suggest

Answer 23

+ charge of nucleus is made up of small discrete particles called protons

Question 24

what is meant by an atom being unstable

Answer 24

it wants to react with another atom to gain a full outer shell

Question 25

when drawing ions what 2 things do you need to do

Answer 25

the charge in the top right corner square brackets all around the ion

Question 26

what did mendeleev do

Answer 26

-he devised the periodic table that organised all of known elements -he predicted undiscovered elements

Question 27

what are the elements arranged by

Answer 27

increasing atomic number(no of protons)

Question 28

what is the mass number

Answer 28

total number of protons and neutrons

Question 29

why did mendeleev create periods

Answer 29

he found that the elements displayed patterns of chemical properties that repeated at regular intervals and formed new rows which we call periods

Question 30

list some trends in group 1 elements

Answer 30

-they become more reactive as you go down the group -they all react violently with water

Question 31

what are trends with halogens

Answer 31

they become less reactive as you go down the group

Question 32

what do atoms in the same period(rows) have the same

Answer 32

no of shells

Question 33

metals form what when they react

Answer 33

positive ions(eg Ca2+) -they lose electrons

Question 34

what do non metals form

Answer 34

negative ions (eg:chlorine) or don't form ions (eg:carbon) -they gain or dont gain electrons

Question 35

what does the positive nucleus do in an atom and why is this important

Answer 35

if the electrons are far away the nucleus cant hold on to them as strongly and so they are easily lost to form positive ions

Question 36

atoms further down the group are more reactive because

Answer 36

they are more likely to lose their electron during a reaction

Question 37

physical properties of metals

Answer 37

-they have metallic bonds -malleable -high melting point and boiling points -shiny -sonorous -good heat and electricity conductors

Question 38

what are physical properties of non metals

Answer 38

-dull -brittle -low melting points and boiling points many being gaseous at room temp -poor conductors of electricity -low density

Question 39

what are the extra properties transition metals have over other metals

Answer 39

-they can form more than 1 ion which are often coloured (eg chromium which forms 2+(which is blue) 3+(which is green ) and 6+(which is orange) -very good catalysts(eg iron in the haber process )

Question 40

list some features of alkali metals

Answer 40

-low density -low melting point -soft -more reactive -react vigorously with water /oxygen and group 7 elements

Question 41

why do alkali electrons become more reactive going down the group

Answer 41

the radius increases so the outer shell gets further from positive nucleus. this means the attractive force between the positive nucleus and the atoms outer most electron meaning the electron can be lost more easily increasing the atoms reactivity

Question 42

how do alkali metals and halogens form ionic compounds

Answer 42

the halogen will gain the alkali metals outer shell electron so both have full outer shells forming oppositely charged ions which are attracted to each other by electrostatic forces called an ionic bond an example of this is table salt they generally form white solids and dissolve in water to form colourless solutions

Question 43

how do alkali metals react in water

Answer 43

reacts vigourously forming metal hydroxide +hydrogen gas

Question 44

after pottasium reacts with water the energy released ignites hydrogen gas .What form do we see this in?

Answer 44

as flames

Question 45

how do alkali metals when heated with chlorine gas

Answer 45

they form white metal chloride salts

Question 46

what happens when alkali metals react with oxygen

Answer 46

they form metal oxides

Question 47

potassium +oxygen forms

Answer 47

ko2 or k2o2

Question 48

sodium +oxygen

Answer 48

na2o2 or na2o

Question 49

what type of molecules are halogens

Answer 49

-diatomic molecules

Question 50

list trends that occur with halogens as you go down the group

Answer 50

-reactivity decreases -boiling and melting points increase

Question 51

why does the reactivty decrease in halogens

Answer 51

because as you go down the group the outermost shell gets further away from the positive nucleus so the force of attraction to pull in extra electron gets weaker

Question 52

how do they react and form ionic bonds with metals

Answer 52

they form halide ions with a 1- ions and these are most common with alkali metals

Question 53

what are all noble gases

Answer 53

-group 0 colourless gases-exist as single atoms and are non flammable -their melting and boiling points increase going down the group

Question 54

what are some colour changes that take place in halogen displacement reaction

Answer 54

Halide salts (e.g. KCl, KBr, KI) are colourless Bromine water is orange Chlorine water is colourless Iodine water is brown

Question 55

list the colours and physical states of the halogens at room temperature

Answer 55

-Fluorine is a poisonous yellow coloured gas and is the most reactive halogen -Chlorine is a green coloured gas. -Bromine is a red-brown volatile liquid which is also poisonous. -Iodine is a grey coloured solid with purple vapours.

Question 56

noble gases trend

Answer 56

bp increases down group have full outer shell (not 8)