Topic 1: Atomic structure and the periodic table

Define an atom

The smallest part of an element that can exist

What is everything made up of?

atoms

Define an element

A substance made up of only one type of atom.

Define a compound

a substance made up of two or more types of different types of elements chemically combined in fixed proportions

Suggest a way of separating a compound back into its elements

chemical reactions

Define mixture

two or more elements or compounds not chemically combined together

Suggest a way of separating a mixture back into its elements

physical separation technique (filtration, distillation, crystallization, chromatography)

Define a molecule

any elements chemically combined

What is fixed in a specific compound?

number of atoms of each element

What is filtration used for?

separating insoluble solid from liquid

define insoluble

solid will not dissolve in liquid

what do state symbols tell us

physical state of chemical

what does (s) tell us?

solid

what does (l) tell us?

liquid

what does (g) tell us?

gas

what does (aq) tell us?

dissolved in water

what equipment do you require for filtration?

filter paper, filter funnel, conical flask

describe method of filtaration

pour mixture into filter paper, filtrate passes through tiny pores in filter paper but solid does not, it stays on the filter paper and mixture is seperated

what is crystallization used for?

separating soluble solid with a liquid

Describe process of crystallization

gently heat mixture to evaporate water and then leave the rest of it to evaporate on its own

why would you use simple distillation

separate disolved solid from liquid but keeping the liquid

what equipment is needed for simple distillation

flask, bunsen burner ,thermometer, condenser, glass tube

give the method of simple distillation

heat solution using bunsen burner until boils, liquid starts to evaporate into vapour and rises into the glass tube, the vapour passes over the thermometer increasing thermometer reading, it goes in the condenser, with the cold water in the vapour condenses into liquid, liquid collected in flask and crystals in the beaker

what can simple distillation be used to produce

drinking water from sea water

what is fractional distillation used for

separate mixture of different liquids with different boiling points

what is the apparatus needed for fractional distillation

flask, fractionating column, thermometer, condenser, beaker

explain method for fractional distillation

gently heat the mixture, both liquids begin evaporating (lower boiling point evaporates easier) the vapours reach fractionating column, condense and drip back into flask where liquids continue evaporating, the repeated cycle increases amount of the lower boiling point liquid in the fractionating column, it makes its way to fractionating column quicker as warm vapours pass up the column as they reach thermometer and thermometer temperature rises(the vapor with lower boiling point is passing), it passes into condenser and turns into liquid and collected in fresh beaker, the same happens with the other liquid after a while and the liquids are separated

what circulates around the condenser

cold tap water

why would liquids with closer boiling points be harder to separate

several rounds of fractional distillation needed

what does paper chromatography allow us to separate substances based on

different solubilities

describe the method for paper chromatography

draw a pencil line near bottom of chromatography paper and put dots of all colors to be tested along the line, place bottom of paper in solvent, solvent moves up the paper, dissolving ink in coloured dots and carrying it up the paper dissolved in solvent, after a while if there’s only one spot the color is made up of one singular ink, but if there’s two we know the color is a mixture

what is the paper for chromatography called

stationary phase

why do we call paper the stationary phase

it doesn’t move

what is the solvent for chromatography called

mobile phase

why do we call solvent the mobile phase

it moves

what does a pure compound in chromatography produce

single spot in all solvents

what does a mixture in chromatography produce

separation into different spots (depending on solvent)

why does paper chromotagraphy work

different substances have different solubilities

what is a more soluble substance attracted to

mobile phase

why do we draw starting line is pencil

if drawn in pen, the pen ink would dissolve in solvent and move up the paper

what are elements and compounds represented by

symbols

what did ancient greeks believe about atoms

tiny spheres that can’t be divided

what did scientists discover in 1897

atoms have electrons

what did discovery of electrons tell scientists

atoms aren’t tiny spheres that can be divided

describe the plum pudding model

atom is ball of positive charge with negative electrons embedded in

describe what happened in the alpha scattering experiment

fired alpha articles at gold foil, most particles passes straight trough gold without changing direction, sometimes repelled and deflected

what charge do alpha particles have

positive

what did the fact that most particles went through gold foil tell scientists

atoms are mainly empty space

what did the fact that some alpha particles were deflected tell scientists

centre of atom has positive charge

what did the fact that some alpha particles repelled tell scientists

centre of atom had a lot of mass (nucleus)

what did the nuclear model contain

negative electrons, empty space, positive nucleus

What did Bohr say about electrons and the nuclear model

electrons orbit nucleus at fixed distances

what are the orbits Bohr talked about called now

shells

What did scientists find about the positive charge in nucleus in nuclear model

it was due to protons

what does number of protons determine

amount of positive charge in nucleus

20 years after the nuclear model, what did Chadwick find out

nucleus also contains neutral particles (neutrons)

what is the radius of an atom

1×10^-10m

what is radius of nucleus

1×10^-14m

define relative charge

charge of one particle compared to another

what is protons relative charge

+1

what is neutrons relative charge

0

what is electrons relative charge

-1

what is an atom’s overall charge and why

none as number of protons is same as number of electrons

define relative mass

mass of one particle compared to another

what is relative mass of protons

1

what is relative mass of neutrons

1

what is relative mass of electrons

1/2000

where is most of the mass in an atom

nucleus

what does each symbol in the periodic table have

atomic number and mass number

what is the number on the bottom of a symbol of element

atomic number telling you number of protons and electrons

what is the number on top of symbol of an element

mass number telling you numbers of protons and neutrons

how do you work out number of neutrons

mass number-atomic number

what do all atoms of same element have

same number of protons

define isotopes

atoms of same element with different number of neutrons

define ion

atom with an overall charge as they’ve lost or gained electrons

define abundance in context of isotopes

how common an isotope is

define relative atomic mass

weighted average of the masses of the atoms of the isotopes

what is the relative atomic mass equation

(mass number of isotope 1 *percentage abundance of isotope 1) +(mass number of isotope 2 *percentage abundance of isotope 2)/100

what do electrons exist in

energy levels/shells

what is the energy level of electron

2 electrons (first shell) 8 electrons (second shell) 8(third shell)

what does group number of element tell us about number of electrons

same number of electrons in outer shell

what is group 0 called

noble gases

how are elements in periodic table arranged

in columns known as groups

what do all elements in a group have

similar chemical properties

What did Dobereiner discover about elements

elements with similar chemical properties often came in threes (triads)

what is an example of triad

lithium, sodium and potassium (all react rapidly with water)

what is Newland's’ law of octaves

every 8th element reacted a similar way

what was an issue of Newlands’ theory

sometimes elements with different properties grouped up

What did Mendeleev develop

first modern periodic table

How did Mendeleev develop the first modern periodic table

arranged all elements in order of increasing atomic weight and switched order of specific elements if needed so they fit group patterns and left gaps in the periodic table for undiscovered elements

What did Mendeleev predict

properties of undiscovered elements based on other elements in the same group, he was correct

diffrences between mendeleev’s and modern periodic table

now elements arranged in order of atomic number (no. of protons) when Mendeleev made his table protons weren’t discovered so he ordered with atomic weight, where some elements appeared in wrong weight due to isotopes and group 0 hadn’t been discovered at Mendeleev’s time

what are noble gases like

very unreactive

why are noble gases unreactive

all atoms have full outer shell

why are noble gases stay gases at room temperature

boiling points below room temperature

what increases as we go down group 0

boiling point of noble gases

where do you find metals in periodic table

left and centre

what side of the periodic table are non metals on

right side

what metals are highly reactive

group 1 and 2

what metals are less reactive generally

transition metals