Topic 2 + 12 Flashcards
state one difference in physical properties of isotopes
(isotope with lower mass number) has lower boiling point/melting point/density than (isotope with higher mass number)
DIFFERENT MASS IS NOT ACCEPTED
explain why chemical properties of isotopes are the same
because they have the same (either one of these is accepted)
1. electron configuration
2. arrangement of electrons
3. same number of protons AND electrons
define the term “isotopes of an element”
atoms of same element with different numbers of neutrons
-> same chemical properties, different physical properties
define “empirical formula”
simplest (whole number) ratio of moles of each element present in a molecule
define “molecular formula”
actual numbers of moles of each element present in a molecule
define “first ionization energy”
energy needed to remove one mole of electron from the ground state of one mole of the gaseous atom
explain the large increase between nth and (n+1)th ionization energies
nth electron comes from pth energy level AND (n+1)th electron comes from (p-1)th energy level.
electron in (p-1)th energy level is closer to nucleus therefore is exposed to greater effective nuclear charge
explain the general increase in successive ionization energies of element
successive electrons are more difficult to remove because each is taken from more positively charged ion, therefore experiencing increased electrostatic attraction
valence electrons
electrons in the outermost shell/energy level of an atom
core electrons
electrons that are not valence electrons and do not participate in chemical bonding
percentage yield
actual yield / theoretical yield x 100
why experimental yield may be greater than theoretical yield
temperature greater than 273K / pressure less than 100kPa
line spectrum
shows discrete number of individual lines at specific points in the visible range
continuous spectrum
shows all colors/wavelengths/frequencies of visible light
atomic number
number of protons
mass number
number of protons + neutrons
cations
lost electrons, positive charge
anions
gained electrons, negative charge
mass spectrometer
used to measure the mass of individual atoms,
basically incomprehensible therefore uses relative mass instead,
used to determine the relative atomic mass of an element from its isotopic composition
horizontal axis: mass/charge ratio of different ions on the carbon-12 scale
vertical axis: percentage abundance
percent abundance
relative amounts of two isotopes
electromagnetic (EM) radiation
comes in different forms of different energy, small portion can be seen as visible light
all EM radiation travels at same speed but have different wavelengths and frequency
frequency
number of waves that pass a point in 1 second
absorption spectrum
produced when EM radiation is passed through a collection of atoms and some of the radiation is absorbed and used to excite the electrons in the atoms from a low energy level to higher energy level.
transmitted radiation relative to incident radiation can be measured
ground state
when electron is in the lowest unoccupied energy level
excited state
when electron is in a higher energy level but is unstable
photon
one packet of energy (quantum),
particle of light
moving electrons
- when an atom falls from excited state to ground state, light of specific frequency (v) is produced
- when an atom moves from ground state to excited state, light of specific frequency is absorbed
ionization energy
energy to remove an electron from the ground state of an atom in a mole of gaseous atoms
emission spectra
produced when photons are emitted from atoms with excited electrons returning to a lower energy level
line emission spectrum of hydrogen
provides evidence for existence of electrons in discrete energy levels which converge at higher energies
orbital
- each orbital has defined energy state for given electronic configuration and chemical environment
- can hold two electrons of opposite spin
Aufbau principle
states that electrons are placed into orbitals of lowest energy first
Cu
(Copper)
exception to Aufbau principle:
[Ar] 4s^1 3d^10
because of full shell stability
Cr
(Chromium)
exception to Aufbau principle:
[Ar] 4s^1 3d^5
because of half shell stability
losing electrons
- loses paired electrons in an orbital first
- loses electrons in 4s first before 3d
limit of convergence at higher frequency
corresponds to the first ionization energy in an emission spectrum
hydrogen spectrum
- absorption: lower level -> higher level
- emission: higher level -> lower level
- converges at higher energy level
- UV radiation: absorption when n=1 -> higher level, emission when higher level -> n=1
- visible light: absorption when n=2 -> higher level, emission when higher level -> n=2
- IR: absorption when n=3 -> higher level, emission when higher level -> n=3
exceptions to ionization energy trend
- First ionization energy of boron (B) is less than that of beryllium (Be) <group 2>
-> for beryllium, first ionization potential electron comes from 2s orbital which is closer to nucleus and experiences higher electrostatic attraction than first electron of boron which comes from 2p orbital - First ionization energy of oxygen is less than that of nitrogen <group 15>
-> for both nitrogen and oxygen, the first electrons come from the 2p orbital, but all electrons of nitrogen in the 2p orbital are unpaired whereas for oxygen there is one set of paired electrons in one of the 2p orbitals. Due to the repulsion between electrons in that orbital, the first electron of oxygen would be easier to remove than that of nitrogen.
