1 - Atomic structure and periodic table

Question 1

What are the relative masses and charges of the subatomic particles?

Answer 1

Question 2

What is the atomic number?

Answer 2

The atomic number is the number of protons in the nucleus of an atom

Question 3

What is the mass number?

Answer 3

The mass number is the total number of protons and neutrons in the nucleus of an atom

Question 4

How to calculate the number of neutrons?

Answer 4

Number of neutrons = mass number - atomic number

Question 5

What are isotopes?

Answer 5

Isotopes are atoms of the same element with the same atomic number, but with a different number of neutrons causing a different mass number.

Question 6

How are ions formed?

Answer 6

Ions on the other hand are formed when atoms either gain or lose electrons, causing them to become charged

Question 7

What are the properties of isotopes?

Answer 7

Isotopes have similar chemical properties but different physical properties

Question 8

What are the chemical properties of isotopes?

Answer 8

Isotopes of the same element display the same chemical characteristics
This is because they have the same number of electrons in their outer shells

Question 9

What are the physical properties of isotopes?

Answer 9

Isotopes with more neutrons have a higher mass, density, melting and boiling point and slower rates of diffusion.

Question 10

What is Relative atomic mass (Ar)?

Answer 10

the weighted mass of an atom of an element compared to 1/12 of the mass of an atom of C12

Question 11

What is Relative isotopic mass?

Answer 11

Mass of an individual atom of a particular isotope relative to 1/12 of mass of C12

Question 12

What is Relative molecular mass (Mr)?

Answer 12

Mean mass of a molecule of a compound relative to 1/12 of an atom of C12

Question 13

What is Time of Flight (TOF) Mass Spectrometry?

Answer 13

Form of mass spectrometry records the time for each ions to reach a detector.

A spectra can be produced to show isotopes present

Question 14

what are the stages of mass spectrometry?

Answer 14

A mass spectrometer measures the masses of atoms and molecules

Produces positive ions that are deflected by a magnetic field according to their mass - to - charge ratio (m/z). I also calculates the relative abundance of each positive ion displays this as a percentage.

Positive ions can be atoms molecules or fragments of molecules.

Question 15

How can the relative molecular mass of diatomic molecules be determined?

Answer 15

Some elements and compounds contain 2 or more atoms covalently bonded together. If these substances are analysed by mass spectrometry. The relative Mr of the element or compound can be obtained by observing the peaks.

Question 16

What is a molecular ion peak?

Answer 16

Is the peak with the highest m/z ratio in the mass spectrum, M peak

Question 17

What is a quantum shells?

Answer 17

Electrons can only exist in certain well defined energy levels called quantum shells.

Question 18

How are the electrons arranged in the first 4 quantum shells?

Answer 18

Electrons in the 1st quantum shell have the lowest energy for that element. 1st Quantum level is located closest to the nucleus then second then third.

Question 19

How are quantum shells divided into subshells?

Answer 19

Each quantum shell apart from first can be divided into subshells with different energy levels.

Second quantum shell has 2 sub shells 2p and 2s. 2p has a higher energy level than 2s

Third quantum shell divided into 3 subshells, 3s, 3p, 3d,. Electrons in 3p have a slightly higher energy level than 3s, and those in 3d have slightly higher than 3p

The 4th quantum shell is divided into 4 subshells, Labelled 4s, 4p, 4d and 4f, 4f having the highest energy level.

Question 20

What is an orbital?

Answer 20

Electrons are held in clouds of negative charge called orbitals. Different types of orbitals like S,P,D,F each one can hold up to 2 electrons with opposite spins and has a different shape.

Question 21

How many electrons are in each subshell?

Answer 21

S = 2 ( 1 x 2 )
P = 6 ( 3 x 2 )
D = 10 ( 5 x 2 )
F = 14 ( 7 x 2 )

Question 22

How many electrons are there in each quantum shell?

Answer 22

1 - 2
2 - 8
3 - 18
4 - 32

Question 23

What is Spin - Spin pairing?

Answer 23

With orbitals electrons pair up with opposite spins so that the atom is as stable as possible. Electrons in the same orbitals must have opposite spins. Represented by arrows.

Question 24

What are the 3 rules for electron configuration?

Answer 24

Lowest energy orbital is filled first.
Electrons with the same spin fill up an orbital before pairings begin.
No orbital holds more than 2 electrons.

Question 25

What is the first ionisation energy?

Answer 25

The energy required to remove an electron from each atom in one mole of atoms to form one mole ions in the gaseous state.

A(g) > A+(g) + e-

Question 26

What is the second ionisation energy?

Answer 26

The energy required to remove an electron from each singly charged positive ion of one mole of a positive ion in the gaseous state. energy required to overcome forces of attraction

A+(g) > A2+(g) + e-

Question 27

How is the emission spectra evidence for different energy levels?

Answer 27

When atoms in the gaseous state are given energy by heating them, the electrons move to the higher energy levels. Eventually they return back to the lower energy levels and emit electromagnetic radiation as they do so.

This can be analysed using a spectroscope shows that the atoms do not emit radiation across whole electromagnetic spectrum. Only specific to the element. All atoms of the same element radiate the same frequencies called line spectrum.

Question 28

What is successive ionisation energies?

Answer 28

When further electrons are removed from an element. The first electron is easy to remove the next 8 there is a steady increase in ionisation energy. More energy is required because as electrons are removed, the electrostatic forces of attraction between the nucleus and the electrons increases. More energy is required to overcome this energy

Question 29

How are electrons removed in a sodium atom?

Answer 29

The last 2 electrons to be removed are in the first quantum shell, the one that has the lowest energy level. The next 8 electrons are in the second quantum shell which has lower energy than the third. First electron to be removed is in the third quantum shell of highest energy level.

Question 30

Why are the electrons in the last quantum shell removed first?

Answer 30

If an electron already has a high energy then the energy needed to be removed is not large. However an electron that is in the first orbital like 1s needs a considerable amount of energy to be removed. The closer an electron is to its nucleus more energy needed to remove from atom

Ionisation energy = Energy of the electron when removed - Energy of electron when in the orbital

Question 31

What factors determine the energy of the electrons?

Answer 31

The number of electrons shielding - The greater the number of electrons the greater the electron - electron repulsion within the orbitals. each electron shields the other from the effects of nuclear charge this increases the energy of the electrons.

Nuclear charge - The greater the nuclear charge of an element (number of protons) decreases the energy of the electrons since they are attracted more strongly

Orbital level - The higher the orbital level the high the energy level higher quantum shell.

Question 32

What are the trends in ionisation energies?

Answer 32

Along the period - First ionisation energy increases as the number of protons increase atomic radium decreases increases the attraction between the nucleus and the electrons this therefore decreases the energy in the outermost electron increasing first ionisation energy. electron removed from same subshell. Similar shielding.

Down a group - First ionisation energy decreases as nuclear charge increases number of protons increases. There is increasing atomic radius and shielding of electrons. One new quantum shell is added each time increases the energy.
On each new quantum shell outer electron has increased repulsion, An extra shell increases shielding.

Question 33

What are the factors affecting first ionisation energy?

Answer 33

distance from nucleus atomic radium
size of nuclear charge
shielding by inner shell

Question 34

What does successive ionisation energies look like on a graph?

Answer 34

When successive ionisation energies are plotted on a graph sudden large increases indicate a change in energy level. This is because the electron is removed from an orbital closer to the nucleus so more energy is required to do so.

Question 35

Where do the orbitals correspond on the periodic table to?

Answer 35

Question 36

What are the exceptions to the rule with electron configuration?

Answer 36

If electrons are unpaired they are therefore unbalanced. It produces a natural repulsion between the electrons making the atom unstable. Electrons take on a different arrangement

Question 37

What is periodicity?

Answer 37

Periodicity is a regularly repeating pattern of physical and chemical properties with increasing atomic number.

Question 38

How is there periodicity in the periodic table?

Answer 38

There is a regular repeating pattern of electronic configurations like in period 2 from 1s2 2s through to 1s2 2s2 2p6 same quantum shell

Other examples include trends in atomic radius, melting point and boiling point, temperatures first ionisation energies and reactions.

Question 39

How is the periodic table arranged?

Answer 39

Periodic table arranges the element according to their proton number. Elements in the same period have the number electron shell and quantum shell. Elements in the same group have the same number of outer electrons.

Question 40

How does Periodicity link to atomic radius?

Answer 40

Atomic radius of an element is a measure of the size of the atoms. It distance from nucleus to outer electron.

Along a period atomic radius decreases. Due to increased nuclear charge for the same number of electron shells. outer electron is closer to the nucleus due to greater attraction.

Down a group atomic radius increases. An outer shell electron is added each time. increasing distance from nucleus to outer shell due to decreased attraction reducing atomic radius. More shells create shielding lest attraction

Question 41

What are the physical properties of period 2?

Answer 41

The melting point of the period 2 elements peaks towards the middle of the period due to different bonding strengths and structures.

Lithium and Beryllium have metallic bonding which is increased due to their charges. Be higher than Li due to more free electrons the electrostatic forces are stronger

Boron and carbon form giant ionic lattices. Very strong covalent bonds require a lot of energy to break meaning high melting and boiling points

Nitrogen Oxygen and Florine have simple molecular and covalent bonds. Weak van der waals forces. These IM forces dont require energy to break

Question 42

How does the ionisation energies change across period 2?

Answer 42

First ionisations generally increase across period 2. Due to increasing atomic radius and nuclear charge.

Boron and oxygen are exceptions due to the first electron removed from the oxygen atom is one of 2 paired electrons. The presence of 2 electrons in an orbital increases electron - electron repulsion in an orbital. Less energy required to remove one of these electrons than in a nitrogen atom.

Question 43

What are the physical properties of period 3 elements?

Answer 43

Sodium, Magnesium and Aluminium are all metals with metallic bonding and have a giant lattice structure. + charge increases their MP due to more electrons are released so attraction force increases.

Silicon is a very strong covalent structure require a lot of energy to break forces.

Phosphorus and Sulphur are simple covalent structures with weak Van der Waals forces. Not much energy required.

Question 44

How does First ionisation increase in period 3?

Answer 44

First ionisation follows a general increase in period 3. Due to decreasing atomic radius and increase nuclear charge. So outer electrons held more strongly.

Aluminium and Sulphur are exceptions due to electron configurations unpaired electrons which require less energy to remove resulting in lower first ionisation energy.

Question 45

What do P and S orbital look like?

Answer 45

Question 46

Why does new subshells create a lower ionisation value?

Answer 46

Electron removed is in the same subshell
greater nuclear charge.
New subshell higher energy level

Question 47

Why are zinc and strontium not transition metals?

Answer 47

Both has last electrons in the d orbital
Neither form a stable ion forms incomplete subshells