Atomic Structure

Question 1

What are the three subatomic particles that make up the atom?

Answer 1

Protons, Neutrons and Electrons

Question 2

What are electrons?

Answer 2

Electrons are subatomic particles that have a charge of -1 and a relative mass of 1/2000. They are found in electron orbitals around the nucleus of the atom.

Question 3

What are protons?

Answer 3

Protons are subatomic particles that have a charge of 1+ and a relative mass of 1. They are found in the nucleus of the atom.

Question 4

What are neutrons?

Answer 4

Neutrons are subatomic particles that have a charge of 0 and a relative mass of 1. They are found in the nucleus of the atom.

Question 5

What is the atomic number and mass number?

Answer 5

Atomic number = the number of protons in an atom
Mass number = the number of protons and neutrons in an atom

Question 6

How are ions formed?

Answer 6

Ions are formed when an atom gains or loses electrons. Positively charged ions are called cations while negatively charged ions are called anions.

Question 7

What are isotopes?

Answer 7

Isotopes are atoms of the same element with the same number of protons but a different number of neutrons. Isotopes share the same chemical properties, but different physical properties.

Question 8

What is the difference between mass number and relative atomic mass?

Answer 8

Mass number is the exact single value of the mass of one isotope while relative atomic mass is the average mass of an element from all of its isotopes.

Question 9

What did John Dalton describe atoms as at the start of the 19th century?

Answer 9

He described atoms as solid spheres, and that different solid spheres made up different elements.

Question 10

What did J.J Thompson add to the model of the atom in 1897?

Answer 10

He discovered the electron, which showed that atoms weren’t solid and indivisible. This new model was known as the ‘Plum Pudding Model’

Question 11

What did Ernest Rutherford add to the model of the atom in 1909?

Answer 11

He conducted his famous gold foil experiment and proposed the new nuclear model of the atom where a tiny positively charged nucleus is surrounded by a ‘cloud’ of negative electrons- meaning most of the atom is empty space.

Question 12

What did Niels Bohr add to the model of the atom?

Answer 12

He realized that in the nuclear model of the atom, the electrons would actually spiral down and collapse so he developed a theory that electrons exits in shells or energy levels. When electrons move between shells they emit or absorb electromagnetic radiation.

Question 13

What was the problem that scientists later found with the Bohr model?

Answer 13

Scientists found that not all electrons have the same energy, and further refined the shells to contain sub-shells.

Question 14

What is relative atomic mass?

Answer 14

The average mass of an atom of an element on a scale where an atom of carbon-12 is 12

Question 15

What is relative isotopic mass?

Answer 15

The mass of an atom of an isotope of an element on a scale where an atom of carbon-12 is 12

Question 16

What is relative molecular mass?

Answer 16

The average mass of a molecule on a scale where an atom of carbon 12 is 12

Question 17

What are the four steps to finding relative masses using a mass spectrometer?

Answer 17

1) ionisation
2) acceleration
3) ion drift
4) detection

Question 18

What are the two ways of ionizing a sample for mass spectroscopy?

Answer 18

Electrospray ionization and electron impact ionization

Question 19

How does electrospray ionization work for mass spectroscopy?

Answer 19

The sample is dissolved and then pushed through a small nozzle at high pressure. A high voltage is applied to it, causing each particle to gain a H+ ion. The sample is turned into a gas made up of positive ions. (in a vacuum)

Question 20

How does electron impact ionization work for mass spectroscopy?

Answer 20

The sample is vaporized and an ‘electron gun’ is used to fire high-energy electrons at it. This knocks one electron off each particle, so they become +1 ions.

Question 21

How does acceleration work for mass spectroscopy?

Answer 21

The positively charged ions are accelerated by an electric field so that they all have the same kinetic energy. (lighter ions move faster than heavier ions)

Question 22

How does Ion drift work for mass spectroscopy?

Answer 22

The ions enter a region with no electric field, so they just drift through it. Lighter ions will drift faster than heavier ions.

Question 23

How does detection work for mass spectroscopy?

Answer 23

Lighter ions are faster and therefore reach the end of the tube quicker and hit the detector where the charged particles are detected and a mass spectrum is produced.

Question 24

What is a mass spectrum?

Answer 24

It is a graph of mass/charge plotted against the abundance (%)
Height is the relative isotopic abundance
make sure to make a note of which ionization technique has been used as electrospray ionization means H+ is added so mass would be one greater than the relative mass of each isotope

Question 25

How do you calculate relative atomic mass from a mass spectrum?

Answer 25

For each peak, you read the relative isotopic abundance and multiply by the relative isotopic mass. Add together all the values and divide by 100

Question 26

How can mass spectroscopy be used to identify elements?

Answer 26

Elements with different isotopes produce more than one line in a mass spectrum because the isotopes have different masses. This produces characteristic patterns that can be used as fingerprints to identify certain elements.

Question 27

How can mass spectroscopy be used to identify molecules?

Answer 27

1) A molecular ion M+ is formed in the mass spectrometer when one electron is removed from the molecule
2) This gives a peak in the spectrum with a mass/charge ratio equal to the relative molecular mass of the molecule.
3) This can be used to help identify an unknown compound

Question 28

What are the levels of electrons found in atoms?

Answer 28

Energy levels/shells
sub-shells
orbitals

Question 29

What affects the principal quantum number?

Answer 29

The further a shell is from the nucleus, the higher its energy and the larger its principal quantum number

Question 30

What are the names of each subshell and the number of orbitals and thus maximum electron capacity?

Answer 30

s = one orbital = 2 electrons
p = three orbitals = 6 electrons
d = five orbitals = 10 electrons
f = seven orbitals = 14 electrons

Question 31

How many electrons can each shell carry in total?

Answer 31

1st = 2
2nd = 8
3rd = 18
4th = 32

Question 32

What is the phenomenon happening in each electron orbital?

Answer 32

The two electrons in a full orbital spin in opposite directions

Question 33

What are the rules to figure out electron configuration?

Answer 33

1) Electrons fill up lowest energy levels first (except 4s is before 3d even though it has a higher principal quantum number)
2) Electrons fill orbitals singly before they start sharing (Hunds rule/bus rule)
3) For the configuration of ions from the s and p blocks of the periodic table, just remove or add the electrons to or from the highest energy-occupied shell.

Question 34

How can you simplify electron configurations?

Answer 34

To make them smaller you can use noble gas symbols and then just write the extra ones that make it different after.

Question 35

What transition metals have a different electron structure and why?

Answer 35

Chromium and copper donate one of their 4s electrons to fill the 3rd sub-shell as they like a stable half-full or fully full d shell.

Question 36

How do transition metals make ions and how does their electron structure change?

Answer 36

When transition metals become ions, they lose their 4s electrons before their 3d electrons.

Question 37

How does an element’s electronic structure determine its chemical properties?

Answer 37

The outer shell electron number decides the chemical properties of an element
1) the s block elements (Groups 1 and 2) easily lose an electron to form + ions
2) the p block elements (groups 5,6,7) can gain electrons to form - ions
3) groups 4 to 7 can also share electrons and form covalent bonds
4) Group 0 has completely filled outer shells so are inert
5) The d block elements tend to lose s and d electrons to form + ions

Question 38

What are ionization and the first ionization energy?

Answer 38

Ionization is the process of removing electrons from an atom or molecule.
The first ionization energy is the energy needed to remove 1 electron from each atom in 1 mole of gaseous atoms to form 1 mole of gaseous 1+ ions.
The lower the ionization energy the easier it is to form an ion. A higher ionization energy means there is a high attraction between the electron and the nucleus and so more energy is needed to remove the electron.

Question 39

What type of reaction is ionisation and what is the equation for 1st IE?

Answer 39

You need energy to remove an electron so it is an endothermic process. The equation for first IE is X(g) —> X+ + e-

Question 40

What are the factors that affect Ionisation energy?

Answer 40

Nuclear charge: (affected by the number of protons) The more positively charged the nucleus is the stronger the attraction for the electrons is
Distance from nucleus: an electron closer to the nucleus is more attracted than one far away
Shielding: as the number of electrons between the outer electrons and the nucleus increases the outer electrons feel less attraction this is called shielding.

Question 41

What is successive ionization energy?

Answer 41

Removing additional electrons

Question 42

What are second ionization energy and its equation?

Answer 42

The second ionization energy is the energy needed to remove 1 electron from each ion in 1 mole of gaseous 1+ ions to form 1 mole of gaseous 2+ ions.
nth ionisation enegry = X(n-1)+ (g) —> Xn+ (g) +e-

Question 43

How can you interpret successive ionization energies to show electron structure?

Answer 43

1) within each shell SIE increases because electrons are being removed from an increasingly positive ion and there’s less repulsion amongst the remaining electrons, so they’re held more strongly by the nucleus.
2) the big jumps on the graph are from when a new shell is broken into as an electron is now being removed from a shell closer to the nucleus.

Question 44

How can you tell what group an element is from by a graph of successive IE?

Answer 44

Count the number of electrons before the first jump

Question 45

How can you use a graph of successive IE to predict the electronic structure of elements?

Answer 45

Work from left to right and count the number of electrons before each jump to get the number in each shell.

Question 46

What are the trends in the first IE?

Answer 46

1) 1st IE decreases down a group in the periodic table as the distance from the nucleus increases and shielding increases so electrons are less attracted and IE is lower.
2) 1st IE increases across a period as the proton number increases thus there is a stronger nuclear attraction. In addition, there is little shielding as the electrons added are roughly the same energy level.

Question 47

What do the drops between groups 2 and 3 show on a graph of 1st IE?

Answer 47

The s sub-shell is filled and the p is starting to fill which means the s provides shielding that overrides the positive nuclear charge and therefore results in a lower IE and a dip in the graph.

Question 48

What do the drops between groups 5 and 6 show on a graph of 1st IE?

Answer 48

Shielding is identical and the electron is being removed from the same orbital however when having one electron in one orbital it is harder to remove than one electron in one orbital with two in it as the extra electron repels the electron you want to remove, making it easier.

Question 49

Why is ionization important?

Answer 49

you need atoms to be pos charged in order to be accelerated and detected