Atomic Structure

Question 1

Mass number

Answer 1

sum of number of protons and neutrons in the nucleus

Question 2

Atomic number

Answer 2

number of protons in the nucleus. since atoms are electrically neutral, the number of protons is also equal to the number of electrons

Question 3

Isotope

Answer 3

Atoms of the same element with the same number protons but with a different number of neutrons

Question 4

Carbon - 14

Answer 4

• used to estimate the age of organisms
  -process is called carbon dating
  -these isotopes are very penetrating and can be used to treat cancer cells

Question 5

Cobalt -60

Answer 5

• a powerful gamma emitter, making it useful treatment for cancer
• also been used to stop the immune response to transplanted organs in the body
• also used in levelling devices and to sterilize food and spices

Question 6

Iodine 131/ Iodine 125

Answer 6

-131 releases both gamma and beta radiation
- can be used to treat thyroid cancer and detect if the thyroid is functionally correctly
-thyroid will take up the iodine and the radiation will kill part of it
- 125 is a gamma emitter can can treat prostate cancer and brain tumours.

Question 7

Mass spectrometry

Answer 7

• instrument that can be used to measure the individual masses of atoms.
• separates individuals isotopes from a sample of atoms and determine the mass of each isotope.

Question 8

Operation of mass spectrometer:

Answer 8

1. Vaporization: The sample is heated and vaporized, and passed through into an evacuated tube
2. This separates the particles
3. Ionization: The atoms/molecules are then bombarded by a stream of high energy electrons, knocking electrons off the particles, resulting in ions with a 1+ charge
4. Acceleration: The positively charged ions are then accelerated along the tube by means of the attraction to negatively charged plates. The ions pass through the slits, which control the direction and velocity of their motion
5. Deflection: The ions are then passed into a very strong magnetic field, deflecting the ions in a curved path
6. Detection: The ions are detected electronically by a device that measures the location and the number of particles

Question 9

Deflection in a mass spectrometer dependent

Answer 9

• absolute mass of the ion
  -charge of the ion
  -strength of magnetic field
  -velocity of ions

Question 10

Calculation relevant atomic mass

Answer 10

A_r=((relative isotopic mass_1×%abundance_1 )+(relative isotopic mass_2×%abundance_2 )+⋯)/100

Question 11

Bohr Model main ideas:

Answer 11

1. Electrons orbit the nucleus in ring like paths around the nucleus at fixed energy levels. The higher the energy level the farther away the electron is from the nucleus and the higher the energy
2. Orbits further from the nucleus exist at higher energy levels
3. Bohr said that electrons are quantized, meaning electrons can only occur in one energy level or another but nothing in between. The ground state is the energy level an electron normally occupies
4. Electrons can only move from one orbital to another orbital at one time. When electrons absorb energy they move up to a higher energy level. This is called the excited state. When the electron returns to a lower energy level they emit energy. These emissions are not always visible to the naked eye

Question 12

Emission Spectrums

Answer 12

• Emission spectra are produced when photons are emitted from atoms as excited electrons return to a lower energy level
• Each electron transition from a higher energy level to a lower energy level corresponds to radiation with a specific frequency or wavelength
• Emission (line) spectrums are produced by excited atoms as they fall back to a lower energy level and only contain specific colors (wavelengths, frequencies) of visible light
• Every element has its own unique emission (line spectrum). Hence, an element can be identified from its emission spectrum
• Ultraviolet light is produced when electrons drop to the first energy level (Lyman series)
• Infrared is produced when electrons drop to the third energy level (Paschen series)

Question 13

Hydrogen emission spectrum

Answer 13

*The line emission spectrum of hydrogen provides evidence for the existence of electrons in discrete energy levels
* The energy of the lines on the emission spectrum of hydrogen corresponds to the difference in energies between energy levels
* Every element has its own unique emission (line spectrum). Hence, an element can be identified from its emission spectrum
* The Balmer series is the name given to a series of spectral emission lines of the hydrogen atom that result from electron transitions from higher levels down to the energy level where n=2

Question 14

Electromagnetic spectrum

Answer 14

• All electromagnetic waves travel at the same speed, but can be distinguished by their wavelengths
• A smaller wavelengths has a higher frequency, so possess more energy
• A larger wavelength has a lower frequency, so posses less energy
• To sum, as energy increases so does the frequency. So red light has lower energy than violet light which is why UV light is so damaging to the skin, since high energy is more dangerous than low energy
• The electromagnetic spectrum shows the range of all possible frequencies of electromagnetic radiation

Question 15

wavelength

Answer 15

o A wavelength is the distance between two successive crests

Question 16

order of electromagnetic spectrum

Answer 16

The order of the spectrum is radio, microwave infrared, visible, ultraviolet, x-ray and gamma ray

Question 17

Paulis exclusion principles

Answer 17

no more than two electrons can occupy any one orbital and if two electrons are in the same orbital they must spin the oppisite way

Question 18

Aufbau principles

Answer 18

electrons are placed into orbitals of lowest energy’s first

Question 19

Hund’s third rule

Answer 19

orbitals of the same sub-level are filled singly first, then doubly. if more than one orbital in a sub level is available electrons occupy different orbitals with parallel spins.

Question 20

First ionization energy

Answer 20

The minimum amount of energy required to remove one mole of electron from one mole to gaseous atoms to another

Question 21

Factors that influence ionization energy

Answer 21

1. Size of the nuclear charge
2. Distance of outer electron from the nucleus
3. shielding effect

Question 22

Size of the nuclear charge

Answer 22

Size of the nuclear charge
* As the atomic number (number of protons) increases, the nuclear charge increases
* The larger the positive charge, the greater the attractive electrostatic force between the nucleus and all the electrons
* a larger amount of energy is needed to overcome these attractive forces and remove an electron
* As the proton number increases, ionization energy increases:

Question 23

Distance of outer electrons from the nucleus

Answer 23

• The force of electrostatic attraction between positive and negative charges decreases rapidly as the distance between them increases
• Hence electrons in shells (main energy levels) further away from the nucleus, are more weakly attracted to the nucleus than those closer to the nucleus
• The further the outer electron shell is from the nucleus, the lower the ionization energy
• Thus, ionization energies tend to decrease down a group of the periodic table

Question 24

Shielding Effect

Answer 24

• Since all electrons are negatively charged, they repel each other
• The full inner shells of electrons prevent the full nuclear charge being experienced by the outer electrons.
• The greater the shielding of outer electrons by the inner electron shells, the lower the electrostatic attractive forces between the nucleus and the outer electrons
• The ionization energy is lower as the number of full electron shells between the outer electrons and the nucleus increases

Question 25

First Ionization energy trends

Answer 25

increases from left to right across a period

Question 26

PLancks constant

Answer 26

6.63 x 10-34 Js

Question 27

speed of light

Answer 27

3.00 x10^8 ms-1