atomic structure and periodic table Flashcards
the model of an atom consists of what?
a small nucleus and electrons in orbital
who found this current model ?
rutherford
how did rutherford find it
scattering experiment 1911
what does the nucleus consist of?
protons and neutrons
whats the charge of a nucleus
positive
what is the atomic mass
the number of protons and neutrons
how is the atomic mass represented
A
what is the atomic number
the number of protons
how is the atomic mass represented
z
what is an isotope
different atom of the same element, same atomic number but different Atomic mass
what is relative atomic mass
mass of an atom of an element relative to 1/12 t of the mean mass of C-12
what is relative isotopic mass
the isotopic mass of an isotope relative to 1/12 the mean mass of the C-12 isotope
what is relative molecular mass
mean mass of a molecule of a compound relative to 1/12 the mean mass of the C-12 isotope
what is relative formula mass
Mr but used for compounds with giant structures
how are ions formed
when an atom gains or looses an electron
what are they used for
the analytical technique of mass spectrometry
what is time of flight
time of flight records the time it takes for ions of each isotope to reach a detector
what is step 1 of mass spectrometry
ionisation
how is step 1 of mass spectrometry done
atom in gaseous state is bombarded with electrons
what is step 2 of mass spectrometry
acceleration
how is step 2 of mass spectrometry done
positively charged ions are accelerated to a negative detector
what is step 3 of mass spectrometry
ion drift
how is step 3 done
ions are deflected by a magnetic field into a curved path
what is step 4 of mass spectrometry
detection
how is step 4 of mass spectrometry done
+ ions git the - detection plate. they gain an electron, producing a current. the greater the abundance, the greater the current produced
what is step 5 of mass spectrometry
analysis
how is step 5 of mass spectrometry done
current values are used in a combination with the flight times
how can u calculate the Ar using printed spectra
Ar-(m/z x abundance)/ total abundance
what is ionisation energy
the minimum energy required to remove the highest energy electron from an atom in its gaseous state
what is successive ionisation energies
when further electrons are removed- usually requires more energy because as electrons are removed, the electrostatic forces increase between the nucleus and electrons
trend in 1st ionisation across a period
increases as the radius decreases due to more electrons and more electrostatic forces
trend in 1st ionisation down a group
decreases as there are more shells that act as shielding and therefore there are less electrostatic forces
what does a sudden large increase in successive ionisation energies on a graph indicate
a change in energy levels
why is the first ionisation energy of aluminium lower than expected?
it has a single pair of electrons with opposite spin. this means there is a repulsion
what is the current model of electronic configuration based on
- emmission spectra provides evidence for quantum shells
- successive ionisation energies prove quantum shells within atoms and sugest the atoms group
- first ionisation energy
what are electron orbitals
a cloud of negative charge where electrons are held
what are the different types of electron orbitals
S P D & F
what is the shape os the S orbital
spherical
what is the shape of the P orbital
dumbbell
what do the electron orbitals corrispond with
blocks in the periodic table
what periods fall in the S block
periods 1&2
what periods fall in the D block
Transition metals
what periods fall in the P block
3,4,5,6,7&8
what periods fall in the F block
the two at the bottom
how many electrons can the S subshell hold
2 electrons
how many electrons can the P subshell hold
6 electrons
how many electrons can the D subshell hold
10 electrons
what is the energy trend of the orbitals from S-D
the energy of the orbitals increase which means that the orbitals are filled from S-D
whats the order of the orbitals being filled
S P D F
sodium has 11 electrons . how will the configuration be written
Na=1s2, 2s2, 2p6,3s1
how many energy levels does sodium have
3
how many orbitals does sodium have?
4
what is spin in an electron
within an orbital, electrons pair up with opposite spin
why do electrons pair up with opposite spin?
so the atom has maximum stability
how is spin represented
opposite arrows
rule one for writing out electron configurations
the lowest energy orbital is filled first
rule two for writing out electron configuration
electrons with the same spin fill up an orbital first before pairing begins
what is rule 3 for electron configuration
no single orbital holds more than 2 electrons
what is an exception to the rule?
if electron spins are unpaired and therefore unbalanced, it produces a natural repulsion between the electrons
what does a natural repulsion within the electrons result in
a very unstable atom
what happens when the atom is unstable
the electrons may take a different arrangement to improve stability
the 3p4 orbital has a single pair of electrons with opposite spins making it unstable, what then happens
an electron moves to the 4s shell to make it more stable and the configuration is now 3p3 4s1
what does periodicity refer to
the study of patterns of physical atomic and chemical properties
what does the periodic table arrange the elements by
the atomic (proton) number
what do the elements along a period have in common
they have the same number of shells
what do elements down a group have in common?
they have the same umber of electrons in its outer shell
what happens to the atomic radius across a period and why
decreases because there are more electrons which means there is a higher nuclear charge and more inter molecular forces
what happens to atomic radius down a group and why
increases because there are more shells
ionisation energy along a period
increases because of the decreased atomic radius which results in higher attractions
ionisation energy down a group
decreases because of more shells which act as sheilds and higher atomic radius
where do the melting points of period 2 element peak
around the middle
boron and carbon form what?
giant covalent lattices with strong covalent bonds
what bonding does lithium and beryllium have?
metallic bonding
what is the general trend in ionisation energies along period 2
it increases because the atomic radius is decreasing
