Atomic Structure Flashcards
Relative atomic mass
The average mass of an atom of an element compared to 1/12th the mass of an atom of carbon-12
Relative molecular mass
The average mass of a molecule of an element or compound compared to 1/12th the mass of an atom of carbon-12
Isotope
Atoms of the same element with the same number fo protons but a different number of neutrons
Mass number
The total number of protons and neutrons in the nucleus
Atomic number
The number of protons in the nucleus
First ionisation energy
The energy required to remove 1 mole of electrons from 1 mole of gaseous atoms to form 1 mole of gaseous 1+ ions
Second ionisation energy
The energy required to remove 1 mole of electrons from 1 mole of gaseous 1+ ions to form 1 mole of gaseous 2+ ions
Orbital
The region where an electron is most likely to be found
How many electrons does energy level 1 have
2 electrons
How many electrons does energy level 2 have
8 electrons
How many electrons does energy level 3 have
18 electrons
How many electrons does energy level 4 have
32 electrons
How many electrons does orbital p have
2
How many electrons does orbital s have
2
What is the shape and max number of electrons in sub shell s
2 - Max núm of electrons
Shape of sub shell- spherical
What is the max num of electrons in sub shell p
Max num of electrons - 6
Sub shell d max num of electrons
Max num of electrons 10
Sub shell f max number of electrons
Max number- 14
Concentration (g dm^-3) equation
Mass of solute(g) / volume of solution (dm^3)
Concentration (mol dm^-3)
Amount of solute(mol) /vol of solution(dm^3)
Concentration (mol dm^-3)
(Conversion to gdm^-3)
Concentration (g dm^-3)/ molar mass (g mol^-1) aka mr
Relationship between empirical and molecular formula
Empirical formula is the simplest whole number ratio of atoms of each element in a compound.
Molecular formula is the actual number of atoms of each element in a compound.
the lower the ionisation energy…
the easier it is to form an ion
name the 3 factors affecting ionisation energy
- Nuclear charge
-atomic radius
-shielding
what affect does nuclear charge have on ionisation energy
more protons mean more positively charged nucleus is and the stronger the attraction of electrons
what affect does atomic radius have on ionisation energy
attraction falls off rapidly with distance. electron closer will be more attracted than those further
what affect does shielding have on ionisation energy
when number of electrons between outer electrons and nucleus increase the outer electrons feel less attraction to nuclear charge.
lessening of the pull of the nucleus by inner shells of electrons is called shielding.
what does high ionisation energy mean
high attraction between electron and the nucleus so more energy is needed to remove electrons
why do the ionisation energies increase for increasingly positive ions
because there is less repulsion amongst remaining electrons so they are held more strongly by the nucleus
Describe the ionisation stage of electron impact
- high energy electrons are fired at the sample from an electron gun
- this knocks off one electron from each atom or molecule to form a 1+ ion :
X(g) → X+(g) + é
Describe the ionisation stage electronspray ionisation
- the sample is dissolved in a volatile solvent
-it’s injected through a fine hypodermic needle at a very high voltage
- the particles gain a proton and become ions :
X(g) + H+(g) → XH+(g)
describe the acceleration of ions stage
the ions are accelerated using an electric field so that all the ions have the same kinetic energy
describe the separation of charges ions stage
- ion drift the ions then enter the flight tube
- ions with different masses have a different time of flight
-the lighter ions travel faster and take less time to reach the detector
describe the detetection stage
- the detector is a negatively charged plate- a current is produced when the ions hit the plate- the more ions
Explain why the second ionisation energy is greater than the first ionisation energy
Electron removed from positive ion
Explain why ionisation energy of every element is endothermic
Energy is needed to overcome attraction between negative electron and the nucleus
State an explain the general trend in first ionisation energies of period 3 elements from sodium to chlorine
Bigger nuclear charge
Electrons closer to nucleus
Smaller atomic radius
So increase
Started how oxygen deviates from general trend in first ionisation energies
Two pairs of electrons in (3)p orbital which repel each other
Why does aluminium deviate from the first ionisation energy trend from Na to Ar
Electron further away from nucleus so less energy needed
Why is second ionisation energy of sodium greater than second ionisation energy of magnesium
Na looses electron from a lower orbital less shielding in Na
Why does sodium have a smaller melting point than magnesium
Na fewer protons smaller attraction between nucleus and delocalised electrons
Explain why it is necessary to ionise molecules when measuring their mass in a TOF mass spectrometer.
Ions will interact with and be accelerated by an electric field
Only ions will create a current when hitting the detector
