Topic 1 Atomic Structure & Periodic Table Flashcards
What is a mass number?
number of protons and neutrons in the nucleus of an atom
What is a relative isotopic mass? (2 marks)
the mass of an atom of the isotope compared to 1/12th of Carbon-12 (1)
which has mass of 12
What is a relative atomic mass? (Ar)
the weighted mean mass of all isotopes of an element relative to 1/12 of the mass of an atom of carbon-12
What is a Relative Molecular Mass? (Mr)
Aka relative Formula mass (esp when it is an ionic compound)
the sum of Ar present in a molecule
What is an orbital?
A region within an atom that can hold up to two electrons with opposite spins.
Define isotopes (2 marks)
The element with same number of protons but different numbers of neutrons
Definition of first IE (2 marks)
energy needed to remove 1 mole of electrons from a gaseous atom
X (g) -> X+ (g) + e-
Definition of second IE
Energy required to remove 1 mole of electrons from 1 mole of 1+ gaseous ions to form 1 mole of 2+ gaseous ions under standard conditions
What is a successive IE
the energy that is required to remove the electron one after the other
3 factors affecting IE
- nuclear charge (num of protons)
- attraction
- shielding
(- atomic radius that decreases down a period)
What is periodicity?
Pattern/trend of physical/chemical properties repeated across a period
What are the 5 stages off mass spectrometry?
Vapourisation
Ionisation
Acceleration
Deflection
Detection (1+ charge as E- knocked off)
VIADD
The bigger the ion… (in terms of mass spectrometry)
The less the deflection
Only what are detected in mass spectrometry?
Ions (1+ charge)
Why is mass spectrometry taken place in a vacuum?
So don’t slow molecules down from deflections
And prevent collisions with air particles
What does mass spectrometry tell you?
- fragments of ions in a molecules
What does infrared tell you?
- functional groups
- dnf
Define periodicity
In terms of atomic radii of period 2 and 3 elements.
It is the repeated physical and chemical properties across a period (with increasing atomic number)
Atom radii decreases from left to right due to increased attraction between nucleus and e-s
Also repeated in Period 3
what are isotopes?
atoms of the same element with same num of protons but diff num of neutrons
State and explain the trend in first IE down periodic table groups (except G3). 2 marks
Decreases down
- increasing number and energy of subshells
- increasing atomic radius and sheilding
- so lose outer e easier
why is first IE of Boron less than Beryllium, even though Boron has higher nuclear charge?
Be - 1s2 2s2
B - 1s2 2s2 2p1
B’s outer e has higher energy in a higher energy orbital
but there is more electron-electron repulsion in the 2s2 orbital (Be) as opposed to 1 in 2p1 (B)
what is periodicity?
repeating patterns across a period of the periodic table
what is the first IE trend across Period 3? (3 marks)
- due to increasing nuclear charge
- e-s added to the same quantum shells so increase of shielding is minimal
- energy of outer e-s decrease (outweighed by increasing nuclear charge)
[i dont rlly like this Q]
what is the trend in atomic radii across period 3? (3 marks)
decreasing atomic radii
since nuclear charge is increasing
increasing attractive force of electron-electron repulsion, num of outer quantum shell increases
what species of chlorine is responsible for each peak at m/z 70, 72, 74?
35Cl-35Cl+ makes 70
35Cl-37Cl+ makes 72
37Cl-37Cl+ makes 74
dont forget the + sign!!
why is the first IE of sodium lower than magnesium?
sodium has lower nuclear charge
so orbital energy of outer electron in 3s is lower
(always write out electron configuration when asked to compare ie)
more electron-electron repulsion =
greater shielding
Which 2 elements have special electronic configurations?
Chronium (Cr-24) and copper (Cu-29)
What is the electronic configuration of chronium? (Ar=24)
1s2 2s2 2p6 3s2 3p6 4s1 3d5
What is the electronic configuration of copper? (Ar=29)
1s2 2s2 2p6 3s2 3p6 4s1 3d10
Why do isotopes of the same element have the same reactivity?
they have the same electronic config (so same num of e-s)
How are ions deflected in mass spectrometry?
Magnetic field
Why is sodium sulfide’s mp higher than sodium chlorides?
Higher charge (2-) in sulfides than chlorides (1-)
Attractive force between sodium is higher
In terms of fundamental particles, why are isotopes 10-B and 11-Boron have similar chemical reactions?
Both have 5 electrons, identical electronic configurations
Explain why the second ionisation energy of boron is higher than first I.e. (1 mark)
Removing an electron from a +ve ion will need more energy
What is the effect of electron repulsion from opposite spin in orbitals?
When the highest energy electron is in an orbital with another electron, they repel each other, push each other further from the nucleus
Decreases the electrostatic forces of attraction
So less energy needed to ionise
How is an ion deflected?
With a magnetic field
Br has isotopes 79Br and 81Br. Why is there a small peak at 80Br? (2 marks)
Br2 has mass of 158 and 162
Br2 2+ has m/z of 80
Explain why a phosphorus(III) chloride molecule has its shape and bond angle. (2 marks)
Arranged to minimise repulsion
Has 1 lone pair and 3 bonded pairs
Repulsion of lone-bond > bond-bond
Give the formulae of all the molecular ion peaks in the mass spectrum of PCl3.
P has mass num of 31
Cl has 35 and 37 isotopes.
(2 marks)
31P (35 Cl)3 + = 136
31P (35 Cl)2 (37 Cl) + = 138
31P (35 Cl) (37 Cl)2 += 140
31P (37 Cl)3 + = 142
Explain why both water and carbon dioxide molecules have polar bonds but only water is a polar molecule. (4 marks)
- Oxygen is more electronegative than both hydrogen AND carbon
- results in polar bonds w oxygen to carbon and hydrogen
- CO2 is linear, so vectors cancel
- lone pairs of e-s of oxygen forms V shape, vectors don’t cancel
How to draw H3O+ AND OH- ions? (2 marks)
[ ] ^+/-
H3O+ has 2 normal covalent, one lone pair and one zH with 2 e-s from O
OH- has one normal covalent w H, 2 lone pairs, one dot and one cross with negative charge and nothing bonded to it.
How to calculate the numbers of SO2 molecules present in an equilibrium mixture. (1 mark)
moles x avogadro’s constant
What is the main reason for bp of HF to be so much higher than HCl?
stronger intermolecular hydrogen bonds!!!
State all the conditions when magnesium bromide can conduct electricity. (1 mark)
when molten AND dissolved in water
What is the definition of a London force? (3 marks)
- random, instantaneous movement of electrons
- causing an instantaneous uneven distribution of electron density
- result dipole in NEIGHBOURING MOLECULES - causing ATTRACTION
How many electrons are in the third quantum shell? (1 mark)
18
3s2 3p6 3d10
