1. atomic structure (as) Flashcards
give all the charges of the subatomic structures in an atom
positive proton
negative electron
neutral neutron
reactive charges + relative masses of subatomic particles
proton- charge- +1- mass 1
neutron- charge- 0- mass 1
electron- charge-(-1)- mass 1/1836
atomic number and mass number + symbols
atomic- number of protons symbol Z
mass- nucleon number- proton and neutron number- symbol A
how are ions formed
when an atom gains or loses an electron causing them to be charged
physical and chemical properties of isotopes + why
chemical:
. same chemical characteristics- same no of e in outer shell- e take place in chemical reactions ,, determine chem of atom
physical:
.diff neutrons ,, only add mass
. diff densities
. diff mp / bp
calculate mass no + proton no
mass no= no of protons + no of neutrons
no of protons= mass no - no of neutrons
symbol for isotope
chemical symbol followed by a dash and then mass number
isotopes definition
atoms of the same element that contain the same number of protons and electrons but different number of neutrons
relative isotopic mass def
the mass of an isotope relative to 1/12 of a c-12 atom
relative atomic mass def
the average mass of an atom relative to 1/12 of the mass of a carbon-12 atom
what are protons + neutrons called
nucleons
relative formula mass MR how is it calculated
(total mass of a substance)
add up the relative atomic masses of all atoms present in formula
ex.H2 2x1=2
Relative atomic mass formula
AR= (relative abundance1 x mass isotope1) + ( relative abundance2 x mass isotope2) /100
what happens when a compound is analysed in a mass spectrometer
vaporised molecules are bombarded with a beam of high speed electrons
they knock off an electron from some molecules causing molecular ions
ionisation energy def
the amount of emery required to remove one mole of electrons from each mole of gaseous atoms of an element to form a mole of gaseous ions
ionisation energies measured under standard conditions + units of IE
. 298k
. 101kPa
units kilojoules per mol (kJ/mol)
second ionisation energy def
energy required to remove one mole of electrons from one mole of gaseous +1 ion to form one mole of gaseous 2+ ions
draw first IE and second IE of x
x —> x+ (g) + e-
x+ —-> x2+ (g) + e-
why does successive IE of an element increase
because once you remove outer electron from an atoms you form a positive ion
removing an electron from a positive ion is more difficult than a neutral atom
more electrons removed attractive forces increase due to decreased shielding and more protons than electrons
side of first IE is affected by
- size of nuclear charge
- distance of outer electrons from nucleus
- shielding effect of inner electrons
- spin pair repulsion
IE across a period
generally increases due to :
. nuclear charge increases across period
. causing atomic radius to decrease as outer shell pulled close to nucleus ,, decreases distance between nucleus and outer e
. shielding by inner electrons remains constant as e enter same shell
. becomes harder to remove across period
. more energy required some IE increases
dips in trend for IE across period
beryllium and boron because boron 2p sub shell further away from nucleus
nitrogen and oxygen because oxygen has more spin pair repulsion in 2p orbital
what happens to IE between last element in period and first element in next period
decrease in IE because
. increased distance between nucleus and outer e bcs in new shell
. increased shielding in inner e because of new shell
. these factors outweigh nuclear charge increases across
IE down a group
decreases because:
. no of protons increases ,, nuclear charge increases
. atomic radius increases
. distance between nucleus and outer electron increases
. shielding by inner shell electrons increases
. factors outweigh nuclear charge ,, easier to remove the outer electron
IE decreases
what do electrons do around the nucleus in energy shells
move rapidly
if energy increases they can jump to a higher energy level
process is reversible ,, can return to their original energy level when they emit energy
frequency or energy is exactly the same when being emitted or absorbed
what happens when the energy electrons emit is mixture of different frequencies
thought that many electrons jump between energy levels and the emitted energy is visible and can be analysed by passing rethought a diffraction grating and results to line emission spectrum
explain line emission spectra
each line is a specific energy value
packets of energy called quanta
in the blue end lines get closer together -convergence
lines converging towards the higher end electrons reaching for max amount of energy
successive IE first e to fourth removed
first- removed has low IE due to spin pair repulsion of e
second- more difficult because there is no spin pair repulsion
third-much more difficult bcs closer to nucleus
fourth- most difficult bcs no longer full orbital + less spin pair repulsion
what does the jumps on the successive IE graphs show
change of shell small jumps are change in sub shell
electron configuration def
the arrangement of electrons in an atom
principle quantum shells
used to number the energy levels
the lower the principle quantum number the closer the shell is to the nucleus
where electrons are arranged around nucleus
the higher the principle quantum number what does it do to energy of shell and distance from nucleus
the greater the energy of shell
the further away from the nucleus
formula to calculate how much each principle quantum number can hold electron
2n^2
orbitals can exist at
specific energy levels and electrons can be only found at these specific levels
how many orbitals in each sub shell
s: one orbital
p: three orbitals
d: five orbitals
f: seven orbitals
types of sub shells
s
p
d
f
s orbital shape + size
spherical shape
size of s orbital increases with increasing shell number
p orbital shape
dumbbell
hunds rule
electrons will occupy separate orbitals in same sub shell to minimise repulsion and have spin in same direction then start to pair up in opposite direction
pauli exclusion principle
orbital can only hold two electrons and they must have opposite spins
sub shell energy order + exception
s<p<d<f
except 3d which has slighter higher energy than 4s
when something is said to be degenerate it means
all the orbitals in the same sub shell have the same energy
chromium configuration + copper configuration
Cr= 1s2 2s2 2p6 3s2 3p6 3d5 4s1
cu= 1s2 2s2 2p6 3s2 3p6 3d10 4s1
where in periodic table would s p d f block
s- g1/2
d- metal
p- g7/8
f- below periodic table
melting point trend of period 3 (2 is the same)
increases up until silicon
silicon is highest mp
after silicon mp decreases significantly
bonding in period 3 elements
Na-Al: metallic
Si- cl: covalent
structure of elements in period 3
Na to Al: giant metallic
Si: giant molecular
P to Ar: simple molecular
metallic elements formed
positive ions arranged in a giant lattice in which ions are held together by a sea of delocalised electrons
meltallic bonding explained in Na- Mg- Al
Na donates one electron
Mg donates two electrons
Al donates three electrons
,, Al electrostatic forces between 3+ion and negatively charged electron
Si why does it have highest mp
giant molecular structure which Si atom is held together to neighbouring atoms by strong covalent bonds
mp between P, S , Cl , Ar
simple molecules
covalent bonds within molecules are sting but between molecules only weak instantaneous dipole-dipole forces ,, doesn’t take much energy to break intermolecular forces
atomic radius
distance between nucleus and outermost electron or an atom
atomic radius name in metals and nonnmetals
metals- metallic radius
non metals- covalent radius
across period what happens to atomic radii + why
radii decreases
bcs no of protons and electrons increases (nuclear charge)
shielding remains the same
nucleus attracts electrons more strongly ,, pulls them closer to nucleus
,, atomic radius decreases
ionisation energy across period 2/3
IE increases due to
. nuclear charge increases
. atomic radius decreases
. shielding by inner shells electrons remains same
. harder to remove an electron
. more energy needed
dips in the trend for period 3 IE energy trends across period
Mg and Al
slight decrease bcs sulfur has spin pair repulsion in 3p orbital which makes its easier to remove electrons
relative molecular mass def
average mass of a molecule or formula unit compared to 1/12th of the mass of an atoms of c-12
what’s used for relative molecular mass, relative formula mass, relative atomic mass
. simple molecules
. compounds
. ions and atoms
