1.2 Basic ideas about atoms Flashcards
In terms of an atomic nucleus, what is radioactive decay?
process that takes place when an unstable atomic nucleus loses energy by radiation
what is alpha decay?
A type of radioactive decay where an atomic nucleus loses two protons and two neutrons.
It is a helium nucleus
Atomic number is reduced by two and mass number by four, making the element more stable
what is beta decay?
A type of radioactive decay where a beta particle is lost (an electron). And a neutron turns into a proton or vice versa.
Changes atomic number by one mass number, the same
what is positron emission?
Positron emission is also known as beta decay.
Beta plus particle has the same mass, the opposite charge to an electron
When it’s released, it increases the nucleus’ proton number by one. No effect on mass number.
What is electron capture?
process used by unstable, atoms to make them more stable
An electron is drawn into the nucleus and reacts with the proton to form a neutron.
What is Alpha?
helium nucleus
What is Gamma?
Electromagnetic wave
What is Beta
fast moving electron
What is Ionising Radiation?
Atoms being hit by radiation energetic enough to cause them to become ions (due to electrons being knocked off)
Alphas ionising power
strongly ionising (do to being larger, it is more likely to hit something)
Beta ionising power
moderately ionising
Gamma ionising power
weakly ionising (due to being faster, it is less likely to hit something)
what can alpha be blocked by
paper
what can beta be blocked by
aluminium
what can gamma be blocked by
lead
why are some atomic nuclei unstable
- there is an imbalance between protons and neutrons
- they contain too much energy
why do unstable nuclei give out radiation
- they undergo decay to become more stable
- as they release radiation, their stability increases
what is the name of the process where an unstable nucleus gives out radiation to become more stable
radioactive decay
alpha particle response to a magnetic field
Weakly attracted to the negative magnetic plate
Beta particle response to magnetic field
Strongly attracted to the positive plate
Positron response to magnetic field
Strongly attracted to the negative plate
Gamma radiation response to magnetic field
Not affected by the magnetic field (has no change)
define half life
Half-life is the time for the mass of a radioactive substance to decrease to half of its original value
why does radioactive decay occur?
The radioactivity of substance decrease over time, so it can become more stable
Give some uses of radio isotopes
-used in medical traces for diagnostic purposes
-used medically to treat cancerous tumours
-Radio dating
Why is it bad to come in contact with certain types of radiation?
Radiation can damage molecules in a living cell and causes a mutation and DNA. This may make the cell become cancerous.
Molar first ionisation energy definition
energy required to remove 1 mole of electrons from 1 mole of its gaseous atom to form 1 mole of 1+ ions
X(g) –> X+(g) +e-
Molar second ionisation energy definition
the energy needed to remove 1mole of electron in 1 mole of gaseous +1 ions to form 1 mole of gaseous ions with a +2 charge
how does ionisation energy change attraction
The greater the attraction, the greater the ionisation energy
What does attraction depend on?
size of nuclear charge
The distance of the outer electron for the nucleus
The shielding effect by electrons (in filled inner shells.)
size of nuclear charge
- Greater the nuclear charge, greater the attractive force
The distance of the outer electron for the nucleus
- The further the distance, the lower the attractive
force
Is ionisation energy, exothermic or endothermic
Endothermic
The shielding effect by electrons (in filled inner shells.)
- It’s the repulsion between electrons in different shells.
- Electrons are all negative so repel each other.
- The more filled inner shells, the lower the ionisation energy.
On a graph of first ionisation energy, which group occupy peaks
group 0
On a graph of first ionisation energy, which group occupy troughs
group 1
Ionisation energy across a period
increases
ionisation energy down a group
decreases
what is an orbital
a region within an atom that can hold up to 2 atoms with opposite spin
what is a subshell
a division of electron shells separated by orbitals
s, p, d and f
What rules do electrons follow when filling up orbitals
- electrons always enter lowest energy orbital available
- electrons prefer to occupy orbitals on their own and will only pair up if there is no empty orbital of the same energy available.
How many orbitals are there in S-subshell
(and how many electrons would it hold)
1orbital
2 electrons
How many orbitals are there in P-subshell
(and how many electrons would it hold)
3 orbitals
6 electrons
How many orbitals are there in d-subshell
(and how many electrons would it hold)
5 orbitals
10 electrons
How many orbitals are there in F-subshell
(and how many electrons would it hold)
7 orbitals
14 electrons
which electron shells, from 1-4 contain which subshells
1: s
2: s, p
3: s, p, d
4: s, p, d, f
4s orbital is filled before 3p
Explain the origin of emission and absorption spectra in terms of electron transitions
when an electron moves down an energy level, a photon is released
when an electron moves up an energy level, a photon is absorbed
the wavelengths of the photons involved are seen using emission and absorption spectra
What is the difference between absorption spectra and emission spectra
emission spectra =displays lines of emitted photons
absorption spectra = displays spectrum with black lines for missing frequencies (of absorbed photons)
How do you calculate ionisation energy
planck’s constant x avogadro’s constant x convergence limit
how do you calculate frequency
(speed of light)/(wavelength)
put UV, visible light, infrared radiation in order of decreasing energy
UV light
visible light
infrared radiation
transition back to N=1
lymen series
UV
transition back to N=2
Balmer series
visible light
transition back to N=3
Paschen series
infrared
