Atoms, Molecules and Stoichiometry Flashcards
a) define and use the terms relative atomic, isotopic, molecular and formula masses, based on the 12C scale a) define and use the term mole in terms of the Avogadro constant a) analyse mass spectra in terms of isotopic abundances (knowledge of the working of the mass spectrometer is not required) b) calculate the relative atomic mass of an element given the relative abundances of its isotopes, or its mass spectrum a) define and use the terms empirical and molecular formula b) cal
Define relative atomic mass
It is the average weighted mass of one atom relative to one atom of 12C which has a mass of exactly 12 units
Define relative isotopic mass
The mass of one atom of the isotope relative relative to that one atom of 12C which has a mass of exactly 12 units
Define relative formula mass
Mass of one formula unit of a compound compared with 12C where one atom of 12C has mass of exactly 12 units
Define relative formula mass
Mass of one formula unit of a compound compared with 12C where one atom of 12C has mass of exactly 12 units
Define relative molecular mass
Mass of a molecule compared with one atom of 12C which has a mass of exactly 12 units
Define the mole in terms of Avogadros Constant
A mole of atoms is a quantity that contains Avogadros number 6.02x10^23 atoms
State the formula for the mass of an element
Mass of an element = AR of the element /Mr of compound x mass of compound
State the formula linking concentration in g/dm^3, mold 3 and Mr
Concentration in g/dm3 =concentration in mold/dm3x Mr
Define the empirical formula
If a compound shows the simplest whole number ratio of elements in the compound
Define the molecular formula
Shows the real numbers of each element in a molecule of a compound
State the formula used in calculating volumes of gases in the burning of hydrocarbons
CxHy (g) + ( x + y/4) O2 (g) _______ xCO2 (g) + y/2 H20(l)
What is the behavior of particles when they enter an electric field
Protons are attracted to the negative plate
Electrons are attracted to the positive plate
Neutrons remain straight as they have no charge
What causes deflection of the beams of particles
Deflection depends on whether the beams of particles enter the electric field with the various particles having the same speed or same energies
Describe how the beam of particles behave if they have the same speed
Protons are deflected on a curved path toward the negative plate
Electrons are deflected on a curved path towards the positive plate
Neutrons are not deflected as they have no charge
If the Electrons and Protons are travelling with the same speed Electrons are deflected more because their more lighter as compared to the heavier protons
Describe how the beam of particles behave if they have the same energies
Protons are deflected on a curved path towards the negative plate
Electrons are deflected on a curved path toward the positive plate
Neutrons are not deflected
The amount of deflection is exactly the same in the electron beam as the proton beam if the energies are the same but in opposite directions
What does isoelectronic mean
Atoms with the same number of Electrons
What does isotonic mean
An atom with the same number of Neutrons
What does isotopic mean
An atom with the same number of protons
Isotopes have the same number of
Protons and Electrons
Electronic configuration
Same chemical properties
Isotopes of different
Nucleon number
Densities
Masses
Molecular speed
The formular to calculate number of Electrons in an energy levels
2n^2
Where n is the quantum number
As we move away from the nucleus…. Does the energy of Electrons increases or decrease
It increases
When arranging Electrons… Which energy level will be filled first
Electrons will always fill the inner level with low energy level then moves to the outer shell with high energy level
The energy of electrons in the sub-shells increases in the order
s < p < d < f
What is the order in which energy levels are filled
1s, 2s, 2p,3s, 3p, 4s,3d,4p,4d
Describe the shape of the s orbital
It is spherical and non directional
Sizes increases as energy level increases
Describe the shape of the p orbital
It is shaped like a dumb bell
It is directional
The lobes get longer as we increase in energy levels
What is an orbital
Space you likely to meet an electron
Define ionization energy
Ionization energy is the energy needed to remove an electron from a mole of atoms of an element in their gaseous state
What are the factors affecting ionization energies
- Nuclear Charge
- Shielding effect
- Atomic radii
Describe the trends of ionization energy across the period
Ionization energy across a period increases since nuclear charge increases and shielding effect remains constant
Therefore force holding valence Electrons becomes stronger
Shell number remains the same, Proton number increases and Atomic radii decreases
Describe the trends of ionization energy down a group
Ionization energy down a group falls
New shells added decrease
Attraction of nucleus to valence elctrobs decreases
Shielding effect increases
Explain how + nuclear charge affects ionization energy
The greater the number of protons in the nucleus the greater the amount of positive charge
The greater the + charge the greater the attraction force between the nucleus and outer Electrons
More energy is needed to overcome this force hence ionization energy is higher
Explain how size of atom/ion (nucleus and outer Electrons) affects ionization energy
The larger the size of the atom the greater the distance between the nucleus and outer electrons
The greater the distance between the nucleus and outer electron the weaker the force of attraction between the nucleus and outer electron
The outer electrons experience >shielding effect from the inner Electrons
Less energy is need to over come the attraction so IE is low
Explain how shielding effect affects ionization energy
The greater the shielding effect, the weaker the attractive force between the nucleus and outer electrons
Less energy is required to overcome the attractive So, the ionisation energy is lower.
– The greater the shielding effect, the lower the ionisation energy
What is the shielding effect
All electrons are negatively-charged, so they repel each Electrons in full inner shells will repel the outer electrons and so prevent the full nuclear charge being felt by the outer electrons. This is called shielding or screening
When there is a big jump
It shows that we are now moving into an energy level closer to the nucleus
The number of Electrons before the big jump shows the group number of electrons
There is a drop from Group 2 to 3 because
It is easier to remove energy from a higher energy p orbital hence there is a drop in ionisation energy
There is a drop from Group 5 to 6 because
Electrons from Group 5 are singly filled and are more stable compared to the Group 6 electrons pairing which results in increased repulsion
Less energy is needed to remove elctrons in group 6
