1.1 Atomic Structure

Question 1

Which letter is used to represent the atomic number of an atom?

Answer 1

Z

Question 1

What does the atomic number tell us about an element?

Answer 1

Atomic number= number of protons in an atom

Question 1

Wha letter represents mass number?

Answer 1

A

Question 1

How is the mass number calculated

Answer 1

Mass number = number of protons + number of neutrons (total number of nucleons)

Question 1

Define relative atomic mass

Answer 1

Average mass of an element / 1/12 the mass of an atom of carbon 12

Question 2

Why do isotopes have the same chemical properties?

Answer 2

They have the same electronic structure. They may have slightly varying physical properties because they have different masses.

Question 3

What is an isotope of an element?

Answer 3

Different forms of the same element, contain the same number of protons but different numbers of neutrons. They still have the same chemical properties.

Question 4

What does the TOF mass spectrometer do?

Answer 4

The mass spectrometerer can be used to determine all the isoptopes present in a sample of an element to therefore identify elements.

Question 5

What are the 4 stages of the mass spectrometer?

Answer 5

Ionisation, Acceleration, Flight tube/ Ion drift area and Detection

Question 6

Describe Electron impact ionisation.

Answer 6

Question 6

When is electron impact ionisation used?

Answer 6

For elements and substances with low Mr. Electron impact can cause larger organic molecules to fragment.

Question 7

Describe electrospray ionisation.

Answer 7

Question 8

When is Electrospray ionisation used?

Answer 8

For larger organic molecules. The “Softer” conditions of this technique mean fragmentation does not occur.

Question 9

Descibe the acceleration stage of TOF.

Answer 9

Positive ions are accelerated by an electric field (Attracted to a negatively charged plate.)

Question 10

Describe the flight tube stage of TOF.

Answer 10

Question 11

Describe the detection stage of TOF

Answer 11

Question 12

Answer 12

Question 13

State the position, Relative Mass and Relative Charge of a proton, neutron and electron.

Answer 13

Question 13

What is the equation that links Relative atomic mass, isotopic mass and percentage abundance?

Answer 13

Question 13

Answer 13

Question 14

Answer 14

Question 14

What do early models of the atom predict?

Answer 14

Early models of atomic structure predicted that atoms and ions with noble gas electron arrangements should be stable.

Question 14

How does the A level model of the atom show how electrons are arranged?

Answer 14

Principle energy levels numbered 1,2,3,4..
1 is closest to nucleus

Sub energy levels labelled s , p, d and f
s holds up to 2 electrons
p holds up to 6 electrons
d holds up to 10 electrons

Orbitals which hold up to 2 electrons of opposite spin

Question 15

What is the order of increasing energy of sub energy levels from 1s-5p?

Answer 15

1s 2s 2p 3s 3p 4s 3d 4p 5s 4d 5p

Question 16

What is the electron structure of MG2+, if Mg is 1s2 2s2 2p6 3s2 ?

Answer 16

Mg2+ is 1s2 2s2 2p6

Question 17

What is the electron structure of 02-, is O is 1s2 2s2 2p4

Answer 17

O2- is 1s2 2s2 2p6

Question 18

What is the electron structure of Cr3+?

Answer 18

Cr 1s2 2s2 2p6 3s2 3p6 4s1 3d5

Cr3+ [Ar] 4s03d3

Question 19

What is the electron structure of Cu2+

Answer 19

Cu 1s2 2s2 2p6 3s2 3p6 4s1 3d10

Cu2+ [Ar] 4s0 3d9

Question 20

Define First Ionisation Energy.

Answer 20

The energy required to remove 1 mole of electron from 1 mole of gaseous atoms to form 1 mole of gaseous 1+ ions.

Question 21

Define Second Ionisation Energy.

Answer 21

The energy required to remove 1 mole of electrons from 1 mole of gaseous 1 + ions to form 1 moles of gaseous 2+ ions.

Question 22

What factors affect ionisation energy?

Answer 22

1. The attraction of the nucleus
   (The more protons in the nucleus the greater the attraction)
2. The distance of the electrons from the nucleus
   (The bigger the atom the further the outer electrons are from the nucleus and the
   weaker the attraction to the nucleus)
3. Shielding of the attraction of the nucleus
   (An electron in an outer shell is repelled by electrons in complete inner shells, weakening the attraction of the nucleus)

Question 23

What are successive ionisation energies?

Answer 23

The patterns in successive ionisation energies for an element give us important information about the electronic structure for that element.

Question 24

Why are successive ionisation energies always larger?

Answer 24

The second ionisation energy of an element is always bigger than the first ionisation energy. When the first electron is removed a positive ion is formed.
The ion increases the attraction on the remaining electrons and so the energy required to

Question 25

How are ionisation energies linked to electronic structure?

Answer 25

The fifth electron is in a inner shell closer to the nucleus and therefore attracted much more strongly by the nucleus than the fourth electron.
It also does not have any shielding by inner complete shells of electron

Question 26

Why has helium the largest first ionisation energy?

Answer 26

Its first electron is in the first shell closest to the nucleus and has no shielding effects from inner shells. He has a bigger first ionisation energy than H as it has one more proton

Question 27

Why do first ionisation energies decrease down a group?

Answer 27

As one goes down a group, the outer electrons are found in shells further from the nucleus and are more shielded so the attraction of the nucleus becomes smaller

Question 28

Why is there a general increase in first ionisation energy across a period?

Answer 28

As one goes across a period the electrons are being added to the same shell which has the same distance from the nucleus and same shielding effect. The number of protons increases, however, making the effective attraction of the nucleus greater.

Question 29

Why has Na a much lower first ionisation energy than neon?

Answer 29

This is because Na will have its outer electron in a 3s shell further from the nucleus and is more shielded. So Na’s outer electron is easier to remove and has a lower ionisation energy.

Question 31

Why is there a small drop from Mg to Al in first ionisation energy?

Answer 31

Al is starting to fill a 3p sub shell, whereas Mg has its outer electrons in the 3s sub shell. The electrons in the 3p subshell are slightly easier to remove because the 3p electrons are higher in energy and are also slightly shielded by the 3s electrons

Question 32

Why is there a small drop from P to S in first ionisation energy?

Answer 32

With sulfur there are 4 electrons in the 3p sub shell and the 4th is starting to doubly fill the first 3p orbital.
When the second electron is added to a 3p orbital there is a slight repulsion between the two negatively charged electrons which makes the second electron easier to remove.