1.2 Atoms

Question 1

Define an atomic orbital

Answer 1

• region of space around the nucleus of an atom where there is a high probability of finding an electron of a given energy
• up to 2 electrons with opposite spins

Question 2

What are the different types of orbitals?

Answer 2

• s orbital
• p orbitals
• d orbitals
• f orbitals

Question 3

Define ionisation

Answer 3

• the process of removing one or more electrons from an atom to form a positively charged ion
• there is a first, second and third ionisation energy

Question 4

Define the (molar) first ionisation energy

Answer 4

• the energy required to remove one electron from each atom in one mole of its gaseous atoms
• kJ/mol

Question 5

Outline the factors affecting ionisation energy

Answer 5

• attraction of the nucleus (more protons = greater attraction = more IE)
• distance of electrons from the nucleus (force between decreases as the distance increases - further away = lower IE)
• shielding of the nucleus

Question 6

Define and explain the shielding affect

Answer 6

• the repulsion between electrons in different shells.
• inner shell electrons repel outer shell electrons and reduce the effect of the positive nuclear charge
  -the more filled inner shells there are, the smaller the attractive force on the outer electron and therefore the lower the IE

Question 7

What is effective nuclear charge?

Answer 7

The total positive charge pulling the electrons to the nucleus. lt is affected by atomic radius and shielding

Question 8

Explain the impact of atomic radius on IE

Answer 8

The greater the atomic radius the more electron shielding meaning the outer electrons of the atom are easier to remove, resulting in overall lower effective nuclear charge thus IE.

Question 9

What happens to IE as you descend a group?

Answer 9

• decreases
• more shells
• increase in shielding due to shell number and so decreases attraction between +ve nucleus and -ve electrons, therefore easier to remove the outer electron

Question 10

What happens to IE as you go across a period

Answer 10

IE increase across a group as there’s no change in shells or electron shielding but the increase number of electrons and protons increases the attraction of the nucleus making it harder to remove an outer electron

Question 11

Why is the 1st IE of N higher than that of O?

Answer 11

In oxygens electronic configuration it has a paired electron that N does not have. This means that due to the repulsion, it is easier to lose this electron in the first ionisation energy stage than it is in N, making the IE of O lower.

Question 12

What is atomic spectrum?

Answer 12

• spectrum of frequencies of EM radiation that is admitted or absorbed during transitions of electrons between energy levels within in atom

Question 13

How does an absorption spectra form?

Answer 13

• white light shone through vapour of element
• black lines appear in the spectrum where the light
  of some wavelengths has been absorbed
• the wavelengths of these lines correspond to the energy taken in by atoms to promote electrons to higher energy levels

Question 14

How is emission spectra formed?

Answer 14

• atom absorbs white light through its vapour which gives the atom energy, exciting it
• promotes electron to a higher energy level which it is unable to stay at for long as energy levels are quantised
• leaves the excited state and falls to a lower energy level, emitting photons of light

Question 15

The hydrogen emission spectrum

Answer 15

• only 1 electron and so simplest emission spectrum
• consists of separate series of lines mainly in the UV, visible and infrared regions
• only Balmer series in in visible region

Question 16

What is electronic transition?

Answer 16

When an electron moves from one energy level to another

Question 17

The lower an electron falls,

Answer 17

The lower the wavelength and therefore the more energy

Question 18

What is the convergence limit?

Answer 18

The point at which the energy of an electron is no longer quantised as the atom is ionised

Question 19

How do you calculate the IE of a hydrogen atom from the atomic emission spectrum?

Answer 19

• record the convergent frequency from the Lyman series
• use E=hf to calculate the energy of 1 atom
• multiply by avogadros constant for 1st molar IE

Question 20

Equations for E (always in kJ)

Answer 20

E = hf

E = Lhc/y

Question 21

What is radioactive decay?

Answer 21

Where atoms are unstable due to an imbalance of protons and neutrons in the nucleus and so undergo radioactive decay to produce stable fragments

Question 22

Explain alpha decay

Answer 22

• helium nuclei (2P, 2N)
• least penetrating - stopped by paper and skin and only travel few cm in air
• most ionising in the body
• mass decrease by 4 and atomic number decrease by 2

Question 23

Explain gamma decay

Answer 23

• high energy EM wave
• no impact on mass or atomic number
• most penetrating - stopped by lead and concrete and travels a few m in air
• least ionising in body

Question 24

Explain beta decay

Answer 24

• regular and inverse ( beta plus and beta minus)
• high speed, high energy electrons
• atomic number increase by 1

Question 25

Explain beta minus

Answer 25

• electron capture
• orbital electrons captured by a proton leading to the formation of a neutron and the emission of an electron neutrino (ve) (similar to an electron but no charge)
• atomic number minus 1, +ve

Question 26

Explain beta plus

Answer 26

• proton converted into a neutron while releasing a positron (B+ particle similar to electron but +ve charge) and an electron neutrino
• atomic number minus one, + B+ + ve

Question 27

Define first ionisation energy

Answer 27

• energy required to remove one electron from each atom in one mole of its gaseous atoms

Question 28

f=

Answer 28

speed of light
———————
wavelength

Question 29

Explain why it is unlikely that stable atoms of (ION) will form

Answer 29

Large increase between 1st and 2nd IE due to shells/electrons being much closer to nucleus. Energy required is unlikely to occur naturally

Question 30

Why do H atoms emit definite frequencies of light?

Answer 30

Frequency of light depends on the energy absorbed to promote an electron from lower to higher energy levels. Energy levels are quantised so frequency emitted is definite

Question 31

Why are there several series of lines?

Answer 31

Electrons falling to different energy levels when leave excited state

Question 32

Why do the lines within the series converge?

Answer 32

Energy differences decreases and so they eventually merge into 1

Question 33

How does gamma react to an electric/magnetic field?

Answer 33

It is undeflected as it has no charge. A straight line.

Question 34

How does alpha react to electric/magnetic field?

Answer 34

Deflects toward the negative because helium nuclei is positively charged. Gradual and slow deflection due to weight

Question 35

How does beta react to electric/magnetic field?

Answer 35

Deflects to positive pole as it’s a negative particle. Deflects quickly as it’s light

Question 36

Define half life

Answer 36

Time taken for half of the unstable atoms of an isotope to decay

Question 37

What does radiation do to cells?

Answer 37

Damages the DNA of cells which leads to mutations and uncontrolled cell division, resulting in cell death or cancerous tumours forming

Question 38

Uses of radioactive isotopes

Answer 38

• medicine: radiotherapy and medical tracers
• carbon and radiodating
• industry to analyse thickness of foil or paper

Question 39

Frequency and wavelength are

Answer 39

Inversely proportional

Question 40

Frequency is (….) to energy

Answer 40

Directly proportional