Atomic Structure

Question 1

What is the history of the atom?

Answer 1

[Robert Boyle]
- Matter was made up of tiny particles that cannot be subdivided and particles made up different compounds

• Particles were in solids, liquids and gases. Forces between particles made materials solid.

[John Dalton]
>Came up with idea of particles. Particles are in fixed positions in solid but free to move liquids and gases.
>Atoms were indivisible and in-destructive
>All atoms of an element are identical and have the same mass and are identical and have same chemical properties
>Atoms of different elements have different masses (atomic weights) and different chemical properties
> Atoms react to form compound atoms, known as molecules

[Joseph John Thompson]
> Atoms contained electrons
> Proposed that atoms could be divided into smaller atoms
> Electrons have very small mass, about one two-thousandths of the mass of a hydrogen atoms. They are negatively charged
> Said that the sphere of positive charge cancelled the negatively charged electrons making the atom neutral.
> Came up with the plum-pudding model

[ Rutherford]
> Came with the idea that the mass of the atom is not evenly spread
> Mass is concentrated in the centre known as the nucleus
> Rutherford calculated the diameter of the nucleus to be 10^-14
> All positive charged is contained in the nucleus
> Electrons circulate the rest of the atom, being kept apart from repulsion of negative charge

[Mosley and Rutherford]
Nucleus contained positive charged particles called protons and protons determined the position on the periodic table
Protons make half the mass of the atom

[Chadwick]
Identified what are known as neutrons and they have no charge
They have the same mass as protons

[Niels Bohr]
>Electrons orbit what are known as energy levels
>Energy levels are quantised
>Electrons occupy set energy levels

Question 2

Why do we use relative mass?

Answer 2

This is because value of mass is so small

Question 3

What is a nucleon?

Answer 3

Is protons and neutrons put together

Question 4

How do protons in the nucleus stay in the same place when they are same charge (positive & positive)?

Answer 4

They do not repel as strong nuclear force act over the small size of the nucleus and bind the nucleons together

Question 5

How can you identify an element?

Answer 5

By its’ atomic number and its’ mass number

Question 6

What is the mass number a measure of?

Answer 6

An atoms mass compared to other atoms

Question 7

What are stable isotopes?

Answer 7

Isotopes that are not radioactive

Question 8

What determines the chemical properties of an element?

Answer 8

Depends on the number and arrangement of the electron in its atoms

Question 9

How are isotopes different and similar?

Answer 9

The have the same chemical properties

They have slight differences in physical properties, rate of diffusion and nuclear properties

Question 10

What is isotope signature?

Answer 10

Elements that occur in space that contain different percentages of isotopes

Question 11

What does relative atomic abundance?

Answer 11

Is the percentage of each isotope that naturally occurs on Earth

Question 12

What can mass spectrometer be used for?

Answer 12

It can be used to analyse samples in competitive sports for drugs or drug testing in sports

Can be used to identify the mass of an element, an isotope or an molecule - which can be used to identify particles

Question 13

What are the types of spectrometers?

Answer 13

Time of Flight Mass Spectrometer

Question 14

What is mass spectrum?

Answer 14

Is a chart that is produced by a mass spectrometer

Question 15

Why do scientist use relative atomic mass?

Answer 15

As atoms have a very small mass

Question 16

What does relative mean?

Answer 16

Means the mass of one atom compared with another

Question 17

What does Relative Atomic Mass mean?

Answer 17

It means the average mass if an atom compared with 1/12 the mass of a carbon-12 atom

Question 18

Formula for Relative Atomic Mass?

Answer 18

RAM Ar = Average Mass of one atom of an
element
—————————————————————-
1/12 the mass of one carbon 12 atom

Question 19

Formula for Relative Molecular Mass?

Answer 19

RMM (Mr) = Average mass of one molecule
———————————————-
1/12 the mass of one carbon-12 atom

Question 20

What does Relative Molecular Mass mean?

Answer 20

Is the mass of an molecule compared with 1/12 the mass of a carbon-12 atom

Question 21

What does Relative Isotopic mass?

Answer 21

Is the mass of an atom of an isotope of an element on a scale where an atom of Carbon-12 is 12

Question 22

How can Mass spectrometer be used to find Mr values?

Answer 22

1) The sample is vaporised and molecules are introduced into the mass spectrometer
2) Sample is bombarded by electrons - can then knock electrons off the molecule. As a result, producing a positively charged ion called molecular ion (M+)
3) Most of these molecular ions split into fragments by bombarding electrons but some remain intact

=> A line is then represented on a mass spectrum - which represents the relative atomic mass of the sample (if an isotope there is more than one molecular ion peak - as they have different masses)

Question 23

What is ionisation energy?

Answer 23

The energy required to remove an electron from an atom in its gaseous state

Question 24

What does First Ionisation Energy?

Answer 24

The energy required to remove electron

Question 25

What does Second Ionisation Energy?

Answer 25

The energy required to remove the second electron from an atom

Question 26

~Not a flashcard

Answer 26

Must know half equation for first Ionisation Energy

Question 27

What does successive ionisation energies mean?

Answer 27

Is the ionisation energy values for removing the second and subsequent electrons

Question 28

What is Ionisation energies measured in?

Answer 28

KJ mol-1

Question 29

Why do we measure Ionisation energies in KJ mol-1?

Answer 29

The is because ionisation energies for one atom are so small

Question 30

What is the general trend in first ionisation energy in Group 3? How does it provide evidence of shells and sub-shells?

Answer 30

> There is a sharp fall in ionisation energy between neon and sodium and between argon and potassium as electrons enter a new shell
There is an overall increase in first ionisation energy across Period 3 as the positive charge on the nucleus increases and electrons are attracted more strongly.
An increase in ionisation energy for each sub shell as the charge on the nucleus increases and electrons are more strongly attracted
A fall in ionisation energy between magnesium and aluminium as electrons start to fill new sub-shell (3p). Evidence of new sub-shell being filled

Question 31

What is the general trend of First ionisation energies in Group 2 elements?

Answer 31

First Ionisation energies decrease as you go down Group 2 - meaning first electron becomes easier to remove

Question 32

Why does the general trend of First ionisation energies in Group 2 elements go down as you go down Group 2?

Answer 32

> This is because as the number of electron shells between the outer electron and the nucleus increases., the electrons shield the outer electron from the attraction of the nucleus
The radius of each atom increases as you go down Group 2 - the distances between the outer electron and the nucleus is increasing

{As a result, the outer electrons are easier to remove and the first ionisation decreases….. This provides evidence of electron shells}

Question 33

What does First Ionisation energy measures?

Answer 33

Measures how much energy that is needed to remove one mole of electrons from a mole of atom