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A Level Chemistry 🫧💧 > 1.1 Atomic Structure > Flashcards

1.1 Atomic Structure Flashcards

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1
Q

What takes up most of the atom’s mass and volume?

A

The atom’s mass is concentrated in the nucleus.
The orbitals/shells take up most of the atom volume.

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2
Q

What’s the relative mass of an electron

A

0.0005 or 1/2000

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3
Q

Definition of isotopes

A

Isotopes of an element are atoms with same number of protons, but diff number of neutrons.

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4
Q

What decides the physical and chemical properties of an element?

A

It’s the number and arrangements of electrons.
Isotopes have same electron configuration = Sam chemical properties

Physical properties depend on atom’s mass
isotopes have slightly different physical properties (densities, diffusion rates etc)

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5
Q

What’s relative atomic mass (Ar) and relative isotopic mass

A

Relative atomic mass
- the avg mass of an atom of an element
- relative to 1/12 of an atom of C-12
This is an avg so not usually whole number
(Carbon chosen as it’s the agreed standard)

relative isotopic mass
- mass of an atom (wch is an isotope) of an element
- relative to 1/12 of an atom of C-12
Usually a whole number

Eg. Natural sample of chlorine = 35Cl (75%) and 37Cl (25%)
Isotopic masses are 35 and 37
Relative atomic mass is 35.5

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6
Q

What’s relative molecular mass / formula mass (Mr)

A

The avg mass of a molecule (small covalent)
On a scale where the atom C-12 is 12
—> rel formula mass for ionic and giant covalently bonded

To find, add relative atomic mass values of all atoms in molecule.

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7
Q

What’s relative molecular mass / formula mass (Mr)

A

The avg mass of a molecule (small covalent)
On a scale where the atom C-12 is 12
—> rel formula mass for ionic and giant covalently bonded

To find, add relative atomic mass values of all atoms in molecule.

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8
Q

What are electron shells made up of

A

In current accepted atom model, electrons have fixed energies.
Moving around nucleus in regions called shells/energy levels

  • each shell is given a number called the principal quantum number
  • the further shell is from nucleus = higher its energy AND larger principal quantum number.

all electrons in a shell don’t have exact same energy
Shells are divided into sub shells that have slightly diff energies
—> subshells have differed numbers of orbitals
—> they hold up to 2 electrons, which spin in opposite directions

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9
Q

What are the different subshells and the numbers of electrons that fit in them

A

•S
- 1 orbital = 2 electrons max.

•P
- 3 orbitals = 6 electrons

•D
- 5 orbitals = 10 electrons

•F
- 7 orbitals = 14 electrons

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10
Q

What are the subshells and numbers of electrons that make up the first four energy levels/shells?

A

•1st shell
Subshells = 1s (2 electrons)

• 2nd shell
Subshells = 2s, 2p (8 electrons)

• 3rd shell
Subshells = 3s 3p 3d (18 electrons)

• 4th shell
Subshells = 4s 4p 4d 4f (32 electrons)

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11
Q

How to work out electrons configurations in subshells

A
  1. Electrons fill lowest energy subshells first
    (NO.1 DIAGRAM)
  • An exception is 4s has lower energy level than 3d
  • even though principal quantum number = bigger
  • so 4s fills first
  1. Electrons fill orbits singly before sharing (as repel each other)
  2. Noble gas symbol used in configurations to substitute.
    (Eg. Ca [Ar]4s2)
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12
Q

What is subshells notation

A

Eg. 1s^2

1 = energy level / shell (this is principal quantum number (pqn))
S = subshell type
2 = number of electrons in the subshell

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13
Q

How are transition metals different when filling up/emptied

A

• Cr and Cu donate one of their 4s electrons to the 3d subshell
- cos they’re more stable with a half full or full d subshell
- remember that 4s fills before 3d

Cr = 3d5 4s1
Cu = 3d10 4s1

• when transition metals = ions, they lose 4s then 3d electrons

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14
Q

How does electronic structure decide the chemical properties of an element?

A

Number of outer shell electrons decides chemical properties of elements.

•S block elements (1&2) with 1/2 outer electrons
- easily lost to form +ions (inert gas config)

•P block (5, 6 and 7) can gain 1/2/3 electrons
- to form -ions (inert gas config)
- Groups 4-7 can share electrons when forming covalent bonds

•group 0 (inert gases) have completely filled s and p subshells
- don’t need to bother gaining/losing/sharing
- full subshells make them inert

• d block (transitions) tend to lose s and d electrons
- forming +ions

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15
Q

What is ionisation energy (and definition of the first ionisation energy)

A

Ionisation is removal of electrons from an atom or molecule.
An endothermic process taking in energy

• First ionisation energy (or ionisation enthalpy) =
- energy needed to remove one electron from each atom
- in 1 mole of gaseous 1+ ions

An equation for the process / first ionisation of oxygen

O (g) —> O+ + e-
First ionisation energy (+1314J)

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16
Q

What are the 3 points about ionisation energies

A
  1. You must use the gas state symbol (g)
    As ionisation energies are measured for gaseous atoms.
  2. Refer to 1 mole of atoms, not just one
    As stated in definition
  3. The lower the ionisation energy, the easier to form an ion
17
Q

What are the factors affecting ionisation energy

A

High ionisation energy = high attraction between electron and nucleus
So more energy needed to remove it

• nuclear charge
- the more protons in the nucleus,the more positively charged it is
- and stronger attraction for electrons

• distance from nucleus
- attraction falls off rapidly with distance
- electrons close to the nucleus will be much more attracted than vice versa

• shielding
- as number of electrons between outer electrons and nucleus increases
- outer ones feel less attraction to nuclear charge
- cos inner shells of electrons lessen the pull

18
Q

What’s successive ionisation energies

A

They involve removing additional electrons
- you can remove all electrons from an atom, leaving only nucleus
- each time removing an electron,
- there’s successive ionisation energy

• The definition for the second ionisation energy is..
The energy needed to remove 1 electron
From each ion in 1 mole of gaseous 1+ ions
To form 1 mole of gaseous 2+ ions.

Equation for second ionisation of oxygen =
O+ (g) —> O2+ + e- (second ionisation energy is +3388kj/mol)

19
Q

What do successive ionisation energies show on a graph

A

They provide evidence for shell structure of atoms
(DIAGRAM no,2)

  1. In each shell, successive ionisation energies increase
    As electrons are being removed from an increasingly positive ion.There’s less repulsion among remaining electrons
    So held more strongly by nucleus
  2. Big jumps in ionisation energy are when new shells are broken into
    (electrons removed from shells closer to nucleus)
20
Q

How to tell wch group an element belongs to
from graphs of successive ionisation energies

A

—> count how many electrons are removed
before first big jump to find group number

—> These graphs also predict elements’ electronic structure
- from right to left, count number of points before each jump
- to find how many electrons in wch shell

Eg, Na (2 points on right, jump, 8 points, jump, 1 point)
= 2.8.1

21
Q

What are trends in first ionisation energies in groups and periods

A

• the first ionisation energies of elements down a group decrease.

• the first ionisation energies across a period generally increase (harder to remove)
- protons increase = stronger nuclear attraction
- all extra electrons are abt same energy level (even diff orbital types)
- means extra shielding effect OR extra distance to lessen nuclear attraction

NO.4 DIAGRAM
—> first ionisation energies across period

22
Q

What’s trend in ionisation energy down group 2

A

The graph showing first ionisation energies
of elements in group 2 proves shells exist
(successive elements down the group have extra and bigger shells)

  • each element down group 2 has an extra shell
  • inner shells will shield outer electrons from nucleus attraction
  • the extra shells mean outer electrons are far from nucleus
  • so nuclear attraction will decrease

—> hence easier to remove outer electrons
Resulting in lower ionisation energy

(DIAGRAM NO.3)

23
Q

Why and what does the drop between groups 2 + 3 show

A

Eg. Mg and Al (period 3)

Al’s outer el torn is in a 3p orbital (not 3s)
- 3p has little higher energy, so electrons further from nucleus.
- 3p has more shielding from 3s2 electrons
-
- both these factors are strong enough to ignore increased nuclear charge effects
Hence ionisation energy drops a little

This is evidence for theory of subshells.

24
Q

Why is there a drop between groups 5 and 6 in first ionisation energy graph

A

Shielding is same in P (g5) and S (g6) atoms
And electron is being removed from same orbital

  • in P’s case, the electron’s removed
    from a singly occupied orbital
  • but in S, the orbital has 2 electrons

The repulsion between two electrons in an orbital
Means electrons are easier to remove from shared orbitals
—> Evidence for electronic structure model

25
Q

What is a mass spectrometer?

A

—> it measures relative atomic, molecular masses and isotopic abundance.
There are four things that happen
When a sample enters a time of flight (TOF) mass spectrometer

  1. Ionisation
    Two ways of ionising sample
    Are electrospray ionisation and electron impact ionisation
  2. Acceleration
    +ions accelerated by electric field
    So all have same KE
    Meaning lighter ions will move faster
  3. Ion drift
    Ions enter region without electric field
    So will drift through it (lighter ions drift faster)
  4. Detection (detectors detect charged particles - electric current produced when hits it)
    Because lighter ions travel faster in drift region
    They reach detector before heavy ions
    Detector detects charged particles and mass spectrum is produced

diagram no. 5

26
Q

What are the 2 ways of ionising sample in mass spectrometry

A

• electrospray ionisation
- sample is dissolved, pushed through small nozzle at high pressures
- high voltage is applied causing each particle to gain a H+ /proton
- sample is turned into gas consisting of +ions

• electron impact ionisation
- sample is vaporised and
- an electron gun is used to fire high energy electrons at it
- knocking an electron off each particle becoming +ions.

(BOTH in a vacuum)

27
Q

What is a mass spectrum graph

A

It is mass/charge plotted against abundance
—> if an element each line is a diff. Isotope

  • y-axis gives abundance of ions
  • often as percentage
    For an element, each peak’s height gives relative isotopic abundance
    (Eg. 92% of sample is 7^Li isotope)
  • x-axis units are mass/charge ratio (or m/z)

‘

Spectrum (no. 6) when made by electron impact - most of time
(Electron knocks other electrons = +1 ions
So mass/charge ratio of peak is same as rel atomic mass of isotope)

When made by electrospray ionisation
(H+ ion added means mass/charge ratio of each peak
= one unit greater than rel atomic mass of each isotope)

28
Q

How to work out rel atomic mass from spectrum 🟡

A
  • multiply relative isotopic abundance (% or not)
    by relative isotopic mass on x-axis
    = multiply together to get total mass for each isotope

Add up each total
Divide all by sum of relative isotopic abundance (or 100 if percentage)

29
Q

How is mass spectrometry used to identify elements

A

Elements with different isotopes produce multiple lines
In mass spectrums as isotopes have different masses.

This makes characteristic patterns,
wch can be used as ‘fingerprints’ to identify certain elements

Many elements have one stable isotope
Can still be identified in mass spectrum
By looking for a line at their relative atomic mass.

30
Q

How can mass spectrometry be used to identify molecules

A

You can get mass spectrums for molecular samples too.

A molecular ion is formed in mass spectrometer
When one electron is removed from molecule.
—> gives peak in spectrum with mass/charge ratio
Equal to rel molecular mass of molecule

Can be used to identify an unknown compound

31
Q

What does isoelectronic mean

A

It means electronic arrangements are the same in both ions/atoms
Eg, Ca2+ and S2- have the same = [Ar]

32
Q

the maths skills needed in 1.1

A
  • how to find percentage composition
  • find rel atomic mass
  • questions involving both v=d/t and KE equation

A Level Chemistry 🫧💧 (7 decks)

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