1.2 basic ideas about atoms Flashcards
proton
Proton = atomic number
neutron
Neutrons = mass number - atomic
electron
Electrons = number of protons
define isotope
Atoms that have the same number of protons but different number of neutrons
what is Radioactive decay
Process that takes place when an unstable atomic nucleus loses energy by emitting radiation
Alpha decay
Cluster of 2 protons and 2 neutrons, positively charged.
It reduces the atomic number by 2 and mass number by 4.
PRODUCT IS TWO PLACES TO THE LEFT
Beta decay
A fast moving electron and a neutron turn into a proton or a proton turns into a neutron.
Atomic number increases by 1 and the mass number is unchanged. Negatively charged.
PRODUCT IS ONE PLACE TO THE RIGHT IN PT
Position emission
Another type of beta decay (beta +)
Proton converted to a neutron whilst releasing a positron and an electron neutrino.
Decreases proton number by 1 but has no effect on mass number
product is one place to the left in the periodic table
Electron capture
Process to make unstable atoms stable.
Product is ONE PLACE TO THE LEFT
MASS NUMBER UNCHANGED, ATOMIC NUMBER DECREASES BY 1
what are alpha, beta and gamma blocked by?
alpha - least penetrating - absorbed by a few cm of air or a sheet of paper
beta - absorbed by a few mm of aluminium
gamma - most penetrating - absorbed by a few cm of lead or 1m of concrete
How are alpha beta and gamma affected by electric fields
Alpha particles are positively charged + Beta particles are negatively charged so they are both deflected by electric field (alpha to neg plate beta to pos plate)
Gamma stays the same since it’s neutral.
Ionising powers of alpha beta and gamma
Alpha - very strong ionising power
Beta - medium ionising power
Gamma - weak ionising power
Compare the penetrating power of alpha, beta, and gamma radiation
alpha
beta
gamma
Gamma
high energy electromagnetic radiation
Radioactivity half life
Time it takes for half the atoms in a radioisotope to decay.
How does radiation affect living cells
Damages cells and changes the way the cell functions,
Can cause a mutation in DNA which can become cancerous at lower doses and at higher doses the cell can die.
Gamma rays are more dangerous outside body and alpha rays are more dangerous inside body
Radioactivity in medicine
cobalt 60
technetium 99
what is cobalt 60 used for
cobalt 60 is used as a treatment for cancer in radiotherapy
what is technetium 99 used for
-technetium 99m used as a medial radioisotope as a tracer
Radioactivity in radiodating
carbon 14
potassium 40
what is cobalt 14 used for
Caron 14 used to call age of plants and animals as it has a large half life.
what is potassium 40 used for
Potassium 40 to estimate age of rocks.
Radioactivity in industry and analysis
ANALYSIS AND INDUSTRY:
Thickness monitoring of metal strips or foil
Dilution analysis to find mass of a substance in a mixture
how many electrons does s,p,d,f orbitals hold
s shell: spherical, can hold 2 electrons per energy level
p shell: can hold 6 electrons per energy level
3 p orbitals
d shell: long balloons connected at the center, can hold 10 electrons per energy level
f shell: similar to d-shell, only more complicated, can hold 14 electrons
define first ionisation energy
The molar first ionisation energy of an element is the energy required to completely remove 1 mole of electrons from 1 mole of its gaseous atoms to form 1 mole of gaseous ions.
X(g) —— X+ (g) + e-
Ionisation energy is exothermic or endothermic
endothermic
Factors affecting ionisation energy
Nucleus charge - greater the nucleus charge the greater the attraction for the outer electron
Electron shielding - filled inner shells or sub shells of electrons act as shields so the outer electron is shielded from nucleus charge by these shells.
Distance from outer shell from nucleus - attraction decreases the further away the outer electron is from nucleus
Trends in ionisation energies
increases across a period
decreases down a group
why does ionisatio energies increase across a period
increases across a period because number of protons increase and electron shielding remains similar so across a period the require more energy to overcome nucleus attraction.
why does ionisation energies decrease down a group
decreases down a group because atomic radius and electron shielding increases so nucleus attraction with the electron gets weaker making the electron easier to remove.
How do successive ionisation energies tell you which group an element belongs to
a large increase between 2 different successive ionisation energies for example 7 and 8th ionisation energies suggests the 8th electron is being taken away from a new full stable shell.
Therefore there are 7 electrons in its outer shell so belongs to group 7.
Why are 4s orbitals filled before 3d orbitals?
4s are at lower energy so they are filled first
What 2 elements are exception to the rule that 4s orbital is filled first
Chromium and copper
What determines the chemical properties of an element
Electron configuration
Shapes of p and s orbital
S - spherical
P- dumbbell shaped
Absorption spectrum
White light is passed through a vapour of a particular element some wavelengths will be absorbed by the atoms of the elements and removed from the white light.
What’s the difference between absorption and emission spectra
Emission spectra displays lines at frequents of emitted photos with coloured lines and a black background
Absorption displays the entire spectrum with black lines for the missing frequencies of the absorbed photons.
Equation for energy and frequency
E = h x frequency
Equation that links frequency and wavelength
F = speed of light/wavelength
Order of increasing energy of visible light, ultraviolet light and infrared
Infrared - visible light - uv light
Lyman series (ultraviolet)
A set of spectral lines that appear in the UV region when a hydrogen atom undergoes a transition from energy levels n>1 to n=1.
Balmer series (visible )
A set of spectral lines that appear in the visible light region when a hydrogen atom undergoes a transition from energy levels n>2 to n=2.
Paschen series (infrared)
the series of lines in the spectrum of the hydrogen atom which corresponds to transitions between the state with principal quantum number n = 3 and successive higher states
