Atomic Structure and the periodic table

Question 1

Atom

Answer 1

All substances are made of atoms

Question 2

What is an element?

Answer 2

An element is a substance made up of atoms that all have the same number of protons in their nucleus. Elements are represented by one or two letter symbol.

Question 3

What is an compound?

Answer 3

A compounds contain two or more elements chemically combined in fixed proportions and can be represented by formulae using the symbols of the atoms from which they were formed

Question 4

How do you represent equations?

Answer 4

By word equations and balanced symbol equations

Question 5

What is an half equation?

Answer 5

A half equation is used to represent what happens when atoms or ions gain or lose electrons. In half equations:

–> electrons are shown as e-

–> the numbers of atoms of each element must be the same on both sides

–>the total charge on each side must be the same (usually zero)

These are half equations for some reactions where positive ions gain electrons:

Na+ + e- → Na

Pb2+ + 2e- → Pb

2H+ + 2e- → H2

These are balanced as it give a neutral ion

Question 6

What is a mixture?

Answer 6

A mixture consists of two or more elements or compounds NOT chemically combined together

IMPORTANT: The chemical properties of a substance aren’t affected by it being part of a mixture.

Question 7

What does chromatography do and how do you prepare it?

Answer 7

Chromatography
–>it is used to separate different dyes and ink

To prepare:
1) Draw a line in pencil near to bottom piece of chromatography paper
2) Place a small sample of each ink on the pencil line
3)Place the chromatography paper in container
4)Place lid on the container and wait for tje solvent to rise to near to the top of the paper
5)Remove the paper from the container when the solvent has risen close to the top of the paper
END

IMPORTANT: If any dyes in the ink are insoluble, they will stay on the baseline.

Question 8

What are the other types of physical seperations?

Answer 8

A. Filtration
–> Filtration separates insoluble solids from liquids

B. Evaporation
–> Used to separate soluble solids from solutions

Process:

1) Pour the solution into a evaporating dish
2) Slowly heat the solution. The solvent will evaporate and the solution will get more concentrated. Eventually, crystals will start to form.
3) Keep heating the evaporating dish until all you have left are dry crystals.

C. Crystallisation
–> Used to separate soluble solids from solutions

Process:

1) Pour the solution into an evaporating dish and gently heat the solution.
2) Once some of the solvent has evaporated, or when you see crystals start to form, remove the dish from the heat and leave the solution to cool.
3) The salt should start to form crystals as it becomes insoluble in the cold, highly concentrated solution.
4) Filter the crystals out of the solution, and leave them in warm place to dry.

Filtration and Crystallisation can be used to separate Rock Salt

Question 9

How did the atomic model changed over time?

Answer 9

1. John Dalton said that atoms are solid spheres and said that different spheres made up the different elements
2. J J Thomson said that atoms weren’t solid spheres instead he resembled atoms as plum pudding model where the atom was a ball of positive charge with electrons stuck in it.
3. Rutherford did the alpha particle scattering experiments. He fired positively charged alpha particles at an extremely thin sheet of gold.

Most of the particles deflected so the plum pudding model couldn’t be right

Rutherford came with the idea of nuclear model of atom. In this, there’s a tiny, positive charged nucleus at the centre, where most of the mass is concentrated. A ‘cloud’ of negative electrons surrounds this nucleus - so most of the atom is a empty space.

4. Bohr proposed that electrons orbit the nucleus in fixed shells and aren’t anywhere in between. Each shell is a fixed distance from the nucleus.
5. Further elements showed positively charged particles which were protons
6. About 20 years later James Chadwick provided evidence for neural particles.
7. The discovery of neutrons resulted in a new model. Modern nuclear model.

Question 10

What is the differences between plum pudding model and modern nuclear model of atom?

Answer 10

Similarity

• -> Both atoms are neutral overall
• -> Both has electrons

Differences

• -> In modern atom mass is concentrated in nucleus whereas, it is spread all over the atom in plum pudding atom.
• -> Plum pudding don’t have shells of electrons instead electrons are arranged randomly within a sphere of positive charge.
• ->Plum pudding model does not have neutrons or protons, it only has electrons surround by a positive charge
• ->Plum pudding model does not have a nucleus but has a ‘ball’ of positive charge instead

Question 11

What is the relative charge and mass of particles and overall charge of atom?

Answer 11

Proton, 1 , +
Neutron, 1 , 0
Electron, Very small , -

Atoms overall charge is neutral as they have same number of protons and electrons

Question 12

what is the mass number and atomic number?

Answer 12

Mass number - neutron + protons
Atomic number - proton

Number of protons = number of electrons

Question 13

What is an isotope?

Answer 13

isotopes are elements that has the same number protons but different amount of neutrons.

Question 14

What is relative atomic mass?

Answer 14

The relative atomic mass of an element is the average mass of its atoms

Question 15

Relative atomic mass equation?

Answer 15

Relative atomic mass = sum of(isotope abundance x isotope mass number) divided by sum of abundance of all the isotopes

Question 16

How electrons fill energy levels in atoms?

Answer 16

The lowest energy levels are always filled first

Only a certain number of electrons are allowed in each shell:

1st shell : 2

2. shell : 8
3. shell: 8

Question 17

How are the elements,groups in periodic table arranged?

Answer 17

In the periodic table the elements are arranged in atomic mass

The vertical columns are called groups.
IMPORTANT: group number tells you how many electrons there are in the outer shell.

Question 18

Why does elements in the same group has similar properties?

Answer 18

Because they have the same amount of outer electron shell which makes them react in the same way.

Question 19

What was the early attempt to classify elements?

Answer 19

The early periodic table was arranged in order of atomic weight

Question 20

What did Mendeleev do?

Answer 20

Mendeleev put the elements mainly in order of atomic weight but did switch the order if the properties changed.

Also he left gaps for undiscovered elements

Question 21

Explain and describe metals and how the electronci structure effects how they will react

Answer 21

• ->Metals are elements which can form positive ions when they react
• -> They’re towards the bottom and to the left of the periodic table.
• -> Most of the elements in the periodic table are metals

Properties:

• -> have metallic bonding
• -> Strong
• -> Malleable
• -> great at conducting heat and electricity
• -> high boiling and melting points
• -> shiny

Electronic structure
–> Metals to the left, don’t have many electrons to remove and metals towards the bottom have outer electrons which are a long way from the nucleus so feel a weaker attraction. These means that not much energy is needed to remove the electrons so they form positive ions.

Question 22

Explain and describe non-metals and how the electronic structure affects?

Answer 22

• -> non-metals are at the far right and top of the periodic table.
• ->non-metals don’t generally form negative ions when they react

Properties:

• ->Don’t have metallic bonding
• -> dull looking
• -> brittle
• -> aren’t always solid at room temperature
• -> don’t generally conduct electricity
• -> Lower density

Electronic structure

• -> Non - metals has lots of electrons which makes them difficult to form positive ions
• -> where the outer electrons are close to the nucleus, they feel a strong attraction. It’s far more easy for them to either share or gain electrons to get a full outer shell.

Question 23

Explain and describe Transition Metals

Answer 23

Transition metals are typical metals and has the same properties as metals but they have a special propertis too. such as:

• -> They are colourful
• ->They can have more than one ion
• -> They make good catalysts

Question 24

Describe noble gases (group 0) and explain their lack of reactivity

Answer 24

–>Group 0 elements (noble gases) have eight electron in their outer shell which gives them a full outer shell. This makes unreactive.

• -> They are colourless at room temperature
• ->They are non-flammable
• ->They are inert(having little or no ability to react)
• -> The boiling point increases as you go down the group.This is due to increase in number of electrons as you go down which leading to a greater inter molecular forces between them which need to overcome.

Question 25

Describe Group 1 (alkali metals)

Answer 25

–>Group 1(alkali metals) elements have one electron in their outer shell which makes them very reactive and gives them similar properties.

-->They are soft and low density
As you go down in the group:
-->Increasing reactivity as outer electron is more easily lost as the attraction between nucleus and electron decreases because electron is further away from the nucleus
-->Lower melting  and Boiling points
--> Higher relative atomic mass
--> they form 1+ ions

REACTIONS:

• -> When they react with water they produce hydrogen gas and metal hydroxide
• -> They are heated in chlorine gas to produce metal chloride salts
• ->When they react with oxygen they produce metal oxide

IMPORTANT: Group 1 metals are much more reactive than transition metals - they react more vigorously
-They are also dense,strong and hard than the transition metals and also has much lower melting points.

Question 26

Describe Group 7 (halogens)

Answer 26

As you go down in group 7

• -> Less reactive
• -> Higher melting and boiling points
• ->Higher relative atomic masses
• -> Halogens can share electron via covalent bonding with other non-metals so as to achieve a full outer shell.
• -> they form 1- ions
• -> They do displacement reactions