Karteikarten
Basic ideas about atoms
Karten in diesem Stapel (90)
- 1IsotopeAtoms of an element with the same number of protons but a different number of neutrons.
- 2IonParticle where the number of protons is not equal to the number of electrons.
- 3Why do we use relative charge and mass?The masses & charges of the sub-atomic particles are so small, we call proton 1 & charge of +1 & compare the others relative to it.
- 4Give the relative charge and mass relative to each of the sub-atomic particlesProtons: 1, +1
Neutrons: 1, 0
Electrons: Neligible (1/1840), -1 - 5Atomic number = Number of protons = Number of neutrons =number of protons
number of electrons
mass number - atomic number - 6Atomic numbernumber of protons in the nucleus of an atom
- 7Mass numbernumber of protons + number of neutrons in the nucleus of the atom
- 8Why are atoms electrically neutral?The number of negative electrons is equal to the number of positive protons.
- 9What is radiation?*Some isotopes are unstable & split up to form smaller atoms
*Nucleus divides, sometimes releasing protons, neutrons, electrons
*Three types of radiation that can be given off at this point: alpha, beta, gamma - 10Alpha particlesConsist of two protons, two neutrons - helium nucleus - with a positive charge
- 11Beta particlesStreaks of high-energy electrons, emitted from the nucleus, with a negative charge
- 12What are gamma rays?High-energy electromagnetic waves with no mass, no charge, a high frequency & small wavelength
- 13When are beta particles formed?When a neutron becomes a proton in the nucleus - n > P + B
- 14What are the penetrating powers of each type of radiation?Alpha: least penetrating because they are the largest. Stopped by a thin sheet of paper or few cm of air.
Beta particles are moderately penetrating as they are smaller than alpha, but larger than gamma. Stopped by 1m of air or 5mm of aluminium.
Gamma: most penetrating due to high energy & small size. Stopped by several cm of lead or more than m of concrete - 15How does ionisation happen?Alpha, beta, gamma pass through materials, colliding with atoms & knocking electrons off their shells, creating ions.
- 16What is the ionisation of each of the types of radiation?Alpha: strongly ionising, due to being large, slow-moving & carry two positive charges - more successful collisions.Beta: moderately ionising.
Gamma: weakly ionising due to fewer collisions as it is smaller & quicker. - 17How are penetrating power & ionisation linked?*Ionisation involves energy transfer from radiation to the matter it passes through
*As ionisation increases, the energy transfer happens more quickly & penetrating power increases - 18Explain what happens to each type of radiation in an electric fieldAlpha: positive so are deflected towards negative plate. Deflection is small due to large size, but they experience bigger force than beta due to larger charge.
Beta: negative so are deflected towards positive plate. Deflection is large due to small mass.
Gamma: No charge so it is not deflected. - 19Explain what happens to each type of radiation in a magnetic field*Has similar effect to electric field
*When charged particles pass through magnetic field, they experience force called the motor effect
Alpha: deflected so must be charged & direction of deflection means they must be positive
Beta: deflected in opposite direction to alpha so must be oppositely charged
Gamma: not deflected so no charge & do not experience a force. - 20Why is radiation dangerous and how does the dosage effect what damage is done?*Everyone experiences background radiation, but workers in atmospheres of high levels must be carefully monitored to ensure they don't exceed international limits
*Radiation damages DNA of cells, which can change the way it functions & cause it to mutate.
*This can lead to cancerous cells at lower doses & higher doses kill cells - 21What type of radiation is the most dangerous?*Outside the body - gamma because it penetrates the skin, where alpha is stopped by dead skin cells
*Inside the body - alpha because they are easily absorbed into tissues without the epidermis skin has & are highly ionising - 22How is radiation used in medicine?*Cobalt-60 - radiotherapy. Gamma used due to high energy.
*Technetium-99m - used as tracer, often to label cells which can be taken to be studied. Gamma as it is easily detected outside of body & doesn't have too long a half life - 23How is radiation used in radio-dating?*Carbon-14 - calculate age of animal/plant remains. All organisms absorb it until they die, and it decays. Amount left is used to see age. Beta. Ling half life.
*Potassium-40 - estimate geological age of rocks. Emits gamma & beta. Changes to argon-40 by nucleus gaining inner electron. Measuring ratio of K-40 to Ar-40 gives estimate of life. - 24How is radiation used in analysis?*Dilution analysis - where isotopically labelled substances are used to find mass of substance in a mixture. Useful when a component of complex mixture can be isolated in pure state but not extracted quantitatively
*Automatic thickness monitoring - B-emitter on one side of rollers & detector on other. If it is too thick, less radiation is detected & if it is too thin, more radiation will be detected. - 25What effect does each type of radiation have on the atom?*Alpha & beta particle emission mean the formation of a new nucleus with a new atomic number, so the product is a different element
*Gamma ray emission does not affect the structure of nucleus it is emitted from, just reduces the amount of energy it has - 26What affect does alpha radiation have on the mass number and atomic number?*Mass number decreases by 4 & atomic number decreases by 2
*Moves left two places on the periodic table - 27What affect does beta emission have on the mass number and atomic number?*The mass number remains unchanged, but atomic number increases by 1
*Product moves 1 place to the right on the periodic table - 28What affect does electron capture have on the mass number and atomic number?*Inverse beta decay
*One of orbiting electrons is captured by a proton in the nucleus, forming a neutron & emitting an electron neutrino
*The mass number is unaffected but the atomic number decreases by 1
*Product moves 1 place to the left on the periodic table - 29What affect does positron emission have on the mass number and atomic number?*Proton is converted into a neutron, while releasing a positron & electron neutrino
*Positron is a type of beta particle
*Mass number is unaffected but the atomic number decreases by 1
*Product moves 1 place to the left on the periodic table - 30Why isn't there a charge left on the atom after the emission of a beta particle?The new proton is balanced by the new electron.
- 31What is a positron?An electron with a positive charge
- 32Half lifeThe time taken for the mass of a radioactive substance to halve.
- 33When is the concern greatest in relation to half life and radioactive substances?When the half life is linger, there radioactivity remains high for longer, so their most harmful stage lasts for more time.
- 34What is the link between the rate of decay and the number of atoms present in the sample?*Rate of decay is proportional to the number of radioactive atoms present in the sample as the half life is unchanging
*So rate of decay cannot be sped up or slowed down by people
*Rate of decay slows as time passes as there are fewer nuclei left to decay - 35Why must radioactive substances be disposed of carefully?They will never have no radioactivity
- 36Principle quantum numbers, n*The shell numbers
*The lower the value of n, the closer the energy level to the nucleus & the lower the energy level - 37Atomic orbitals*Definition: a region in an atom that can hold up to 2 electrons with opposite spins
*Orbitals of same type are grouped together in subshell
*each orbital can contain 2 electrons
*Each orbital has its own 3-D shape - 38Explain the 'spin' of electrons*Electrons have a property called 'spin'
*For 2 electrons to be in same orbital, they must have opposite 'spin', reducing effect of repulsion - 39What is the 3D shape of an s orbitals?*Spherical
*There is only 1 type - 40What is the 3D shape of p orbitals?* 3 different p orbitals, dumbell shaped lobes
*Known as px, py & pz
*Are at right angles to each other - 41What is the 3D shape of d orbitals?*5 different d orbitals
- 42What is the 3D shape of f orbitals?*7 different f orbitals
- 43How many electrons can each type of orbital hold?s: 2
p: 6
d: 10
f: 14 - 44Electronic configurationarrangement of electrons in an atom
- 45What are the 3 basic rules of electronic configuration?1. Aufbau principle - electrons fill atomic orbitals in order of increasing energy
2. Pauli exclusion principle - maximum of 2 electrons with opposite spins can occupy any orbital
3. Hund's rule - orbitals will first full with 1 electron, each with parallel spins, before 2nd electron is added with paired spin - 46What is the order of filling for orbitals?1s
2s
2p
3s
3p
4s
3d
4p - 47Why does the order not follow as expected?*Expected order is filled up to 3, but 4s subshell is filled before 3d
*Due to increasingly complex influences of nuclear attractions & electron repulsions upon individual electrons - 48What is the electronic configuration written in the simplest form?*Use a core of the previous noble gas in the periodic table
*Eg. Ca = (Ar)4s2 because of argon core, which makes up 18 electrons & there are 2 left - 49What do the arrows represent in the "arrows in boxes method"?*An individual electron
*Clockwise spin - upwards arrow
*Anticlockwise spin - downwards arrow - 50IonisationProcess of removing electrons from an atom
Energy needed to remove each successive electron from an atom is called 1st, 2nd, 3rd, etc. - 51Molar first ionisation energyenergy required to remove one mole of electrons from one mole of its gaseous atoms
- 52Electron shielding/screeningRepulsion between electrons in different shells. Inner shell electrons repel outer shell electrons.
- 53What equation represents the first ionization energy?X(g) > X+(g) + e-
- 54What is the relationship between ionization energy & nuclear attraction?*Electrons are held in their shells by attraction to positive nucleus
*So, greater the attraction, greater the ionisation energy - 55What 3 factors is the ionisation energy dependent on?*Size of positive nuclear charge - greater the nuclear charge, the greater the attractive force on outer electron & greater the ionisation energy
*Distance of outer electron from nucleus - force of attraction between nucleus & outer electron decreases as distance between them increases, so ionisation energy decreases
*Shielding effect - electrons repel each other due to negative charge. Electrons in filled inner shells repel electrons in outer shell & reduce effect of positive nuclear charge. More filled inner shells/subshells there are, smaller attractive force on outer electron & lower the ionisation energy - 56What are the most significant features of the graph to show ionisation energies for first 20 elements?*Peaks occupied by elements of Group 0
*Troughs occupied by elements of Group 1
*General increase in ionisation energy across period, although not uniform - 57Successive ionisation energiesMeasure of energy needed to remove each electron in turn until all electrons are removed from atom
- 58How many ionisation energies does an element have?An element has the same number of ionisation energies as it has electrons
- 59Why do successive ionisation energies always increase?*There is a greater effective nuclear charge as the same number of protons are holding the same number of electrons
*As each electron is removed there is electron repulsion & each shell drawn slightly closer to nucleus
*As distance of electron from nucleus decreases, nuclear attraction increases - 60Why does a successive ionisation energy plot show large increases at certain points?*Due to electrons being on different shells
*A large increase shows an electron has been removed from a new shell closer to nucleus - 61What does a large increase in successive ionisation energy tell us about an atom?*The group its in
*Eg. Li has large jump between 1st & 2nd I.E, so it's in Group 1
Al has large energy jump between 3rd & 4th I.E, so is in Group 3 - 62How do we know what block an element belongs to in the periodic table - s, p, d or f?The block is the same as the type of orbital the last electron is in.
- 63What are the exceptions to the rule of filling the 4s orbital before 3d?Cr (Chromium) & Cu (Copper)
Cr - The 4s orbital only has one electron as the 2nd moves to the 3d orbital where there is less electron repulsion due to not being paired. Makes 3d stable as now 1/2 filled.
Cu - makes 3d completely full - they either like to be 1/2 full or full - 64How does the electron configuration of elements change when they become ions?+ ion - Remove electrons from outer sub shell, unless there are 4s electrons as these must be removed before 3d as easier to get rid of lower energy electrons
- ion - add electrons to outer shell
eg. N3- : add 3 electrons - 65What are the patterns of ionisation energy in terms of groups and periods?*Across a period - general increase due to increase in nuclear charge
*Down a group there is a general decrease due to shielding & increased distance from nucleus - 66Standard ionisation energyProcess when conditions for ionisation energy are 298K & 1atm
- 67Spectrometeran instrument which separates light into its constituent wavelengths
- 68Electronic transitionmovement of electron from one energy level to another
- 69Convergence limitwhen spectral lines become so close together they have continuous band of radiation & separate lines cannot be distinguished
- 70LightForm of electromagnetic radiation
- 71Electromagnetic radiationenergy travelling as waves
- 72What equation are frequency and wavelength related by?c = f x wavelength
where c is speed of light (ms-1)
f is frequency (s-1 or Hz)
wavelength (m) - 73What equation are frequency and energy related by?E = hf
where E is energy (J)
h is Planck's constant (6.63 x 10-34)
f is frequency (s-1 or Hz) - 74Explain the relationship between frequency and energy*Frequency is directly proportional to energy - it increases as energy does
- 75Explain the relationship between frequency and wavelengthFrequency is inversely proportional to wavelength - it increases as wavelength decreases
- 76Electromagnetic spectrumRange of frequencies of EM radiation
- 77What are the patterns of wavelength, frequency and energy through the electromagnetic spectrum?*Energy & frequency increase from radio waves to gamma rays
*Wavelength decreases from radio waves to gamma rays - 78Visible spectrumThe section of EM spectrum where visible light (white light) is - UV to infrared
- 79Explain the absorption spectrum*Atoms & molecules absorb light of certain wavelengths
*So when white light passes through an element, certain wavelengths are absorbed by atoms & removed from light
*Black lines appear on spectrum where light of some wavelengths has been absorbed
*These wavelengths correspond to energy absorbed by atoms to move electrons from lower to higher energy levels - 80Explain the emission spectra*When energy is removed, electrons move from higher to lower energy levels
*Energy is lost as photon (quantum/"packet" of light energy)
*Made of coloured lines (where light is emitted) on black background
*As only certain colours are on an atom's emission spectrum, only photons with certain energy levels are emitted - 81Why are there set lines on a spectra?Energy levels are quantised (specific energy is needed to reach them) so electrons cannot move part way
- 82Where do electrons prefer to be?Lower energy level
- 83What could n=1 also be called?Ground state
- 84Explain how frequency effects lines on a spectraAs frequency increases, lines get closer together because the energy difference between shells decreases.
- 85Name each of the 6 seriesLyman series, n=1 (lines are due to electrons returning to first shell) & is UV region
Bulmer series, n=2 & is visible region
Paschen series, n=3 & is infrared region
Brackett series, n=4
Pfund series, n=5
Humphreys series, n=6 - 86Describe a hydrogen atom's emission spectra*Atoms have 1 electron so give simplest emission spectrum
*Consists of separate series of lines, mainly UV, visible & infrared regions of EM spectrum - 87What is the link between the hydrogen atom and the Lyman series?For Lyman series, convergence limit represents ionisation of hydrogen atom
- 88Explain the convergence limit*Spectral line get closer as frequency & energy increase until they converge to a limit
*Convergence limit corresponds to point where energy of electron is no longer quantised, nucleus loses influence over electron & atom becomes ionised - 89Convergent frequencydifference from n=1 to n= infinity
- 90What role does ionisation have in obtaining a mass spectrum?*Atoms must be ionised so they can be deflected by magnetic field
*The magnetic field allows ions to be separated from each other
*They are ionised by being hit with beam of electrons
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- AS level Chemistry Karteikarten am Basic ideas about atoms, erstellt von Bethan Lewis am 19/09/2016.
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