atomic structure and bonding structure

Question 1

4 key features of chemical reaction

Answer 1

measurable energy change
no atoms are created or destroyed
at least 1 new substance is created
compunds are broken up or formed

Question 2

Crystallisation

Answer 2

Crystallisation separates solutions into their different parts: dissolved solids (solutes) and liquids (solvents).
Crystallisation is performed by heating the mixture so that the solvent evaporates.
Eventually, crystals of the solute (dissolved solids) will form.
We can collect the solvent (liquid) by condensing it as it evaporates.

Question 3

filtration

Answer 3

Filtration separates mixtures that contain insoluble (can’t dissolve) solids and liquids (which are soluble).
Filtration is performed by pouring the mixture through filter paper:
The insoluble solid is trapped by the filter paper.
The liquid runs through the filter paper and is collected below.

Question 4

chromatagraphy

Answer 4

Chromatography separates solutions with a number of different solutes (solids) in the solvent (liquid).
Place a drop of the solution to be separated near the bottom of a piece of chromatography paper. Dip the very bottom of the paper into a suitable solvent. The solvent (liquid) moves up the paper and carries the solutes (solids) in the solution with it.
Different solutes (solids) move at different speeds, so they separate on the paper.

Question 5

Fractional distillation

Answer 5

Separates lots of liquids with different boiling points.
The mixture is slowly heated until the liquid with the lowest boiling point boils and then condenses.
Then we increase temperature slowly to collect (boil then condense) the other fractions.

Question 6

Simple distillation

Answer 6

Separates 2 liquids with different boiling points.
The mixture is heated until the liquid with the lower boiling point starts to boil.
The vapour released passes through a condenser, where the gas cools back into a liquid.
Simple distillation can also separate a solute from a solvent, when the solvent has a lower boiling point than the solute.

Question 7

Thomson’s plum pudding model

Answer 7

In 1897, an English physicist called J. J. Thomson discovered electrons.
Thomson modelled the atom as a ‘plum pudding’ - a ball of positive charge (dough), with negatively charged electrons (currants in pudding) mixed in with the ‘dough’.

Question 8

Rutherford’s nuclear mode

Answer 8

n 1909, Ernest Rutherford discovered that alpha particles could bounce back off atoms.
Rutherford concluded that an atom’s mass is concentrated in the atom’s centre. This was called the “nucleus” and it contained positively charged particles called protons.

Question 9

The modern model

Answer 9

Niels Bohr discovered that electrons orbit (fly around) the nucleus at fixed distances.
In 1932, James Chadwick discovered that some particles in the nucleus have no charge at all. He called them neutrons.

Question 10

what determines element

Answer 10

the number of protons

Question 11

what is an isotope

Answer 11

isotopes are different forms of the same elemnt taht have the same number of protons

Question 12

how to calculate the relative atomic mass

Answer 12

sum of (isotope abundance x isotope mass) / sum of abundance of all isotopes (100)

Question 13

difference between molecule and compund

Answer 13

compunds are 2 or more different elements held togheter by chemcial bonds
molecules 2 or more atoms held togheter by chemical bonds

Question 14

what are mixtures

Answer 14

2 or more substance not chemically combined togheter
easily separate ( physical method)
different substances havent reacted

Question 15

Describe how you would carry out the process of crystallisation.

Answer 15

First, pour the solution into an evaporating dish and heat it using a Bunsen burner.

Stop heating it when crystals start to form (‘point of crystallisation’) and allow it to cool down.

Then either leave it to allow the rest of the water to evaporate, or filter out the crystals using filter paper and a funnel. Lastly, dry the crystals in a warm oven.

Question 16

When Democritus first conceived of atomic theory, around 500 BC, how did he describe atoms?

Answer 16

The smallest possible unit of matter

Small spheres

Separated from each other by empty space

Question 17

How Rutherford developed the nuclear model

Answer 17

In Rutherford’s experiments, alpha particles were fired at a thin sheet of gold foil.
Most particles passed through, but some were deflected off course.
This caused him to hypothesise that there was a dense region of positive charge at the centre of the atom that repelled the alpha particles.
As a result he developed the nuclear model of the atom, in which there was a central positive nucleus, surround by negative electrons.

Question 18

how much electrons can eah shell hold

Answer 18

The shell closest to the nucleus can hold 2 electrons, whereas the outer ones can hold up to 8 electrons.

Question 19

properties of metals

Answer 19

metallic bonding, malleable
conductors
high melting point
shiny
sonorous

Question 20

properties of non-metals

Answer 20

lower densities
brittle
dull in colour
low meltiing and boiling points

Question 21

properties of transition metals

Answer 21

all typical metal properties +
con form more than one ion
catlyst

Question 22

what are properties of alkaline metals-

Answer 22

soft
low density
low melting point
they are much more reactive
tehy get more reactive as they go down
their melting and boiling points decrease as they go down
they are 1+ ion

Question 23

how does alkaline reacts with water

Answer 23

they usually react vigorously and produce metal hydroxide + hydrogen gas

Question 24

Explain why the reactivity of group 1 metals increases as you go down the group.

Answer 24

The reactivity of group 1 elements increases as you go down the group because the atoms become larger, which means that the outer electron becomes further from the nucleus.

This in turn means that the electrostatic attraction between the positive nucleus and the outer negative electron decreases in strength.

As a result the outer electron will be lost more easily, and so the element will be more reactive.

Question 25

For questions involving halogen displacement reactions, you will often be asked about the colour changes that take place.

Answer 25

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

Question 26

Colours and physical states of the halogens at room temperature

Answer 26

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 27

Which two of these properties are seen in group 7 elements?

Answer 27

Their ions usually have a 1- charge

They can form covalent bonds with other non-metals

Question 28

Do the melting and boiling points of the halogens increase or decrease as you go down the group?

Answer 28

Increase

Question 29

key fact about ion forming from group 3 4 5

Answer 29

The transfer of electrons requires a lot of energy.

Groups 1, 2, 6 and 7 form ions very easily. This is because they only need to gain or lose a small number of electrons, and so less energy is required.

Those in groups 3, 4 and 5 do not form ions very easily, because they need to gain or lose a larger number of electrons, and therefore more energy is required.

Question 30

what is ionic bond

Answer 30

Ions with opposite charges will attract each other.

This force of attraction between oppositely charged ions forms an ionic bond
Oppositely charged ions attract each other.

This is called an electrostatic force. This same force is also what attracts protons to electrons within atoms and ions.

Question 31

2 key properties of ionic bond

Answer 31

conduct electricity - only whne melted or dissolved in water
- charged particle that are free to move

Ionic compounds have relatively high melting and boiling points.
This is because ionic bonds are very strong, and a high amount of energy is required to break the bonds.

Question 32

what is a lattice

Answer 32

Ionic structures involve many ions bonded together via ionic bonds.

The solid arranges itself into a regular 3D structure known as a lattice.

Question 33

the correct formula for a nitrate ion:

Answer 33

NO3 -

Question 34

Hydroxide:
Sulphate:
Nitrate:
Carbonate:
Ammonium:

Answer 34

Hydroxide: OH-
Sulphate: SO42-
Nitrate: NO3-
Carbonate: CO32-
Ammonium: NH4+

Question 35

what is a molecular formula

Answer 35

The molecular formula of a substance shows the actual number of atoms of each element present in a compound or mole
For example, the molecular formula for glucose is C6H12O6

Question 36

what ia an emperical formula

Answer 36

The empirical formula of a substance is the simplest, whole number ratio of atoms of each element in a compound. This means that it doesn’t tell you exactly how many atoms there are, just the ratio of the atoms of each element.
For example, the empirical formula for glucose is CH2O, which means that the ratio of carbon : hydrogen : oxygen is 1 : 2 : 1. Or in other words, for every 1 carbon atom, there are 2 hydrogen atoms and 1 oxygen atom.

Question 37

How to find the empirical formula from a molecular formula

Answer 37

Looking at the molecular formula of ethane (C2H6), we can see that the ratio of C : H atoms is 2 : 6

2To get the empirical formula, we need to simplify this ratio as much as possible. You can simplify the ratio 2 : 6 by dividing both sides by 2 - which gives you 1 : 3

3This 1 : 3 ratio means the empirical formula for ethane is 1 carbon atom for every 3 hydrogen atoms.

4So the empirical formula for ethane is CH3

Question 38

How to find the molecular formula from the empirical formula and Mr

Answer 38

First, find the Mr of the empirical formula:

CH3 contains 1xC and 3xH, so 1x12 + 3x1, which equals 15.

See how many times the Mr of the empirical formula (15) goes into the unknown compound’s Mr (30).

30 ÷ 15 = 2

So the empirical formula’s Mr goes into the unknown compound’s Mr 2 times

Look at the empirical formula: CH3, and multiply all the numbers by the multiple you just found (2):

Remember that CH3 is really C1H3
So multiplying all the numbers in CH3 by 2 gives you C2H6
So the molecular formula is C2H6

Question 39

How to find the empirical formula from masses or percentages:

Answer 39

1) Assume 100 g of the compound is present. This changes the percentages given in the question into grams:

Sulfur (S): 50.05% ➔ 50.05 g

Oxygen (O): 49.95% ➔ 49.95 g

2) Convert these masses to moles (moles = mass ÷ Mr):

moles of sulfur (S) = 50.05 g ÷ 32 = 1.564

moles of oxygen (O) = 49.95 g ÷ 16 = 3.122

3) Divide both the mole values you just calculated (1.564 and 3.122) by the lower number of the two (1.5640625), this gives you the smallest whole-number ratio between the two elements (you usually need to round the answer to the nearest whole number, as we do in this example):

Sulfur (S): 1.564 ÷ 1.564 = 1

Oxygen (O): 3.122 ÷ 1.564 = 1.996 (round this to the nearest whole number) = 2

So now you know the ratio of sulfur to oxygen in this compound is 1 : 2

Question 40

In covalent bonding, are electrons transferred between atoms, or shared between atoms?

Answer 40

shared

Question 41

Covalent bonds form between ________ atoms.

Answer 41

non-metallic

Question 42

Which of the following is an example of a simple molecule?

Answer 42

ammonia

Question 43

what rae simple molecules and what are their main roperties

Answer 43

A simple molecule has multiple atoms covalently bonded together. These covalent bonds between atoms are very strong.

Strong covalent bonds between the atoms of each molecule.
Weak intermolecular forces between molecules.
Low melting and boiling points (so normally gaseous as room temperature).
Cannot conduct electricity.

Question 44

how to melt or boil chlorine

Answer 44

break weak forces that exist between molecules = intermolecular forces
therefore it needs low temps. to melt or boil
( howeevr the bonds in between the atoms are very strong)
(the more intermolecular forces the molecule has the stronger the attraction = more energy required to break)

Question 45

what rae giant covalent structures

Answer 45

Every atom is connected by strong covalent bonds
No weak intermolecular forces as there is only one structure
High melting and boiling points
Cannot conduct electricity (except graphite)

Question 46

The halogens exist in different states at room temperature.

Answer 46

Chlorine is a gas at room temperature.
Bromine is a liquid at room temperature.
Iodine is a solid at room temperature and gives off purple fumes.

The reason they are in different states at room temperature is that they have different melting and boiling points. As you go down group 7, the atoms (and thus molecules) get larger. This means there will be more intermolecular forces, and so more energy (and a higher temperature) will be required to break them.

Question 47

what are allotrope

Answer 47

different structure forms o the same elemnt in the same physical state

Question 48

in diamond

Answer 48

each carbon atom is covallently bonded to 4 other carbon atoms
- strong
- high melting point
- doen’t conduct electricity

Question 49

in graphite

Answer 49

each atom bonede to 3 other atond
lots of layers are flat sheet which are held togheter weakly as there are not covalent bonds between them
- soft compare to diamond
- still high metling and boiling point
- each carbon atom has 1 spare delocolised electron

Question 50

why is graphite able to conduct electricity

Answer 50

Graphite is able to conduct electricity.

This is because each carbon atom has one delocalised electron, which can move freely, and so is able to carry charge.

Question 51

why is graphite softer than diamond

Answer 51

Graphite is a lot softer than diamond.

This is because the 2D layers of graphite stack on top of each other with only weak intermolecular forces holding them together.

This means the layers can slide over each other, making graphite easier to break.

Question 52

uses of fullerenes

Answer 52

• form spheres around other moleecules (like a cage)
  mainly used to dilever drugs in body
• industrial catalyst (speed up chemical reactions)
• nanotubes - nanotechology (conduct electricity)
• used to stenghen tennis racket materia

Question 53

what are fullerenes

Answer 53

Fullerenes are allotropes of carbon, made by bending sheets of graphene into hollow structures.

Nanotubes made from these are useful in electronics. This is because each carbon atom has one delocalised electron which can carry charge.

Question 54

What is the formula of the first spherical fullerene produced, known as the Buckminster fullerene?

Answer 54

C60

Question 55

what is metallic bonding

Answer 55

In metallic bonding, each metal atom becomes an ion with a positive charge.
It does this by giving up its outer shell electrons.
These electrons are said to be ‘delocalised’, and are shared across all the ions in the structure.

Question 56

property of metallic bonding

Answer 56

In metallic bonding, electrons are delocalised from the lattice of metal ions.

These electrons can carry charge, and so metal acts as a conductor of electricity.

These electrons can also carry thermal energy, meaning metals are good conductors of heat.

Question 57

Which of these describes an alloy?

Answer 57

A metal combined with one or more other elements

Question 58

why are alloys stronger than pure metals

Answer 58

This is because the atoms/ions of the different elements are different sizes, which disrupts the regular layered structure and so means the layers can no longer slide over one another.

Question 59

Which theory attempts to explain the three states of matter?

Answer 59

Particle (kinetic) theory
Small
Inelastic
Spheres

Question 60

When a gas is heated, which of the following statements are true?

Answer 60

If it’s in a fixed container, the pressure will increase

If it’s in an expandable container, the volume will increase

Question 61

key feautures of nano particles

Answer 61

• large SA to V ration

Question 62

uses of nanoparticles

Answer 62

as catalyst
in medecine
- to deliver drugs around the body
- deliver drugs inside cell
in electrical circuit
- tiny computers chips
silver nanoparticles
- antibacterial propeties
-surgiacl masks
- wound dressings
- reduce the chance of infection

Question 63

some issues

Answer 63

relavly new
we need to regulate them more strict - some peopel think
effects on our bodies aren’t fully understood
may cayse pollution