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Chemistry A Level AQA > 3.1.1 Atomic Structure (PAPER 1) > Flashcards

3.1.1 Atomic Structure (PAPER 1) Flashcards

1
Q

How has model of atomic structure changed over time?

A

1) Billiard Ball- Dalton’s model
-Atom is small hard sphere with no internal structure.

2) Plum Pudding- Thomson
-Atom is sphere of positive charge with negative electrons scattered throughout it.

3) Nuclear Model-Rutherford
-Alpha particle scattering experiment: fired +charged alpha particles at thin sheet of gold foil, most went straight through but some deflected due to hitting a small positive nucleus.
-Nearly all mass concentrated in central nucleus which is +charged.
-Negatively charged electrons orbit nucleus.

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2
Q

Explain current model of the atom

A

-Atom consists of small, dense central nucleus surrounded by orbiting electrons in electron shells.
-Nucleus contains protons + neutrons held together by strong nuclear force.
-Nuclear force is stronger than electrostatic force holding electrons in shells.

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3
Q

Relative charge and relative mass of all subatomic particles?

A

Electron charge is -1, mass is 1/1840
Proton charge is +1, mass is 1
Neutron charge is 0, mass is 1

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4
Q

What is the mass number? What letter?

A

A, number of protons and neutrons.

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5
Q

What is the atomic number? What letter?

A

Z, number of protons

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6
Q

How are isotopes formed?

A

Most combinations of protons and neutrons forming the nucleus are unstable so they decay to form more stable combinations.

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7
Q

What are isotopes?

A

Atoms of the same element with the same number of protons, different number of neutrons.

They have the SAME chemical properties due to the same electronic configuration/electron number.

DIFFERENT physical properties due to different mass number.

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8
Q

What is the relative atomic mass equation?

A 
      total abundance (add all the %'s)
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9
Q

Definition of relative formula mass (Mr)?

A

The sum of all relative atomic masses of all atoms in the formula of the substance.

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10
Q

Definition of relative molecular mass?

A

The average mass of a molecule of a substance relative to 1/12th the mass of a Carbon 12 atom.

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11
Q

Definition of relative atomic mass (Ar)?

A

The average mass of an atom of an element relative to 1/12th the mass of a Carbon 12 atom.

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12
Q

What is a TOF Mass Spectrometer?

A

Gives accurate information about relative isotopic mass and relative abundance of isotopes.

Used to identify elements.

Determines relative molecular mass.

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13
Q

What is the 1st stage of mass spectrometry? 2 types

A

Electrospray ionisation or electron impact.

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14
Q

What is electrospray ionisation?

A

Sample is dissolved in inert, volatile solvent.

This is forced through fine hypodermic needle as a fine spray into a vacuum in the ionisation chamber.

Very high voltage applied to other end of the needle producing tiny + charged droplets due to loss of electrons.

Solvent evaporates leaving 1+ ions.

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15
Q

What is electron impact?

A

An electron gun/filament of wire produces high energy electrons.

These electrons collide with the molecules/ atoms in the sample removing an electron from each particle to produce 1+ ions.

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16
Q

What is 2nd stage of mass spectrometry and what happens?

A

Acceleration

Ions with different masses have a different time of flight.

Ions are accelerated using an electric field so they all have the same kinetic energy.

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17
Q

What is 3rd stage of mass spectrometry and what happens?

A

Ion Drift

Ions enter the flight tube- the lighter ions travel faster and take less time to reach the detector- they have a lower time of flight.

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18
Q

What is the equation for time of flight?

A

d/v or d√m/2KE

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19
Q

What is 4th stage of mass spectrometry and what happens?

A

Detection

The positive ions reach the negatively charged detector plate and produce a flow of charge due to the ions gaining an electron.

The greater the abundance, the greater the current produced.

20
Q

What is the relationship between abundance and current produced?

A

abundance ∝ size of current

21
Q

What is the last stage of mass spectrometry and what happens?

A

Analysis

The mass of ions hitting the detector can be calculated from the time it takes to reach the detector.

Mass spectrum shows number of particles (abundance) of each mass that hits the detector.

22
Q

Definition of ionisation energy?

A

The amount of energy required to remove 1 mole of electrons from 1 mole of gaseous atoms.

Measured in KJmol-1

23
Q

What is the 1st ionisation energy + equation for Li?

A

The amount of energy required to remove 1electron from a neutral atom.

Li(g) —> Li(g)+ + e-

24
Q

What is the 2nd ionisation energy + equation for Li?

A

The amount of energy required to remove 1 electron from a 1+ ion.

Li(g)+ —> Li(g)2+ + e-

25
Q

What is the 3rd ionisation energy + equation for Li?

A

The amount of energy required to remove 1 electron from a 2+ ion.

Li(g)2+ —> Li(g)3+ + e-

26
Q

Why is the 3rd ionisation energy greater than the 2nd or 1st?

A

There is a stronger + charge due to the 2+ ion so there is a greater electrostatic force between the nucleus and the electron that is being removed- more energy needed to remove it.

27
Q

What 3 things affect ionisation energy?

A

Distance from nucleus/atomic radius- if it increases by adding more shells, the IE decreases due to weaker attraction between nucleus and electrons.

Nuclear charge (Z)- If it increases, IE increases due to increased attraction between nucleus and electrons.

Shielding- more shells= more shielding which decreases IE.

28
Q

How does ionisation energy decrease down a group?

A

Eg- down Group 2

Increase in atomic radius: electron being removed is in new energy level further from nucleus= weaker attraction between nucleus and electron.

Extra energy level provides extra shielding for the electron from the positively charged nucleus.

29
Q

How does ionisation energy increase across a period?

A

Eg- across Period 3

There is an increased nuclear charge due to an increase in proton number, electrons experience greater attraction to nucleus as atomic number of atom increases.

Decrease in atomic radius due to pull of the nucleus being stronger and pulling in and shrinking the electron cloud.

Shielding remains mainly the same as electrons are in same energy level (3 for period 3)

30
Q

Examples of exceptions to ionisation energy trends?

A

Be—>B
N—>O
Mg—>Al
P—>S

31
Q

Explain the decrease in ionisation energy between Be and B?

A

Be has electron configuration 1s² 2s²
B has electron configuration 1s² 2s² 2p¹

B has a lower IE as electrons in p orbitals are higher in energy and further from the nucleus than electrons in s orbitals so they require less energy to remove. 2s orbital is more shielded than 2p orbital.

32
Q

Explain the decrease in ionisation energy between Mg and Al?

A

Mg electron configuration= 1s² 2s² 2p⁶ 3s²
Al electron configuration= 1s² 2s² 2p⁶ 3s² 3p¹

Electrons in 3p orbital are further away from nucleus and higher in energy than electrons in 3s orbital so they require less energy to remove. Mg has stable, full subshell which is harder to break into.

33
Q

Explain the decrease in ionisation energy between N and O?

A

N electron configuration=1s² 2s² 2p³
O electron configuration=1s² 2s² 2p⁴

N=⥯ ⥯ ↿ ↿ ↿
0= ⥯ ⥯ ⥯ ↿ ↿

In oxygen, the electron is removed from a doubly occupied 2p orbital. O experiences electron-electron repulsion in this orbital which increases the energy, therefore lowering the ionisation energy. N has more stable electron arrangement.

34
Q

Explain the decrease in ionisation energy between P and S?

A

P electron config= 1s² 2s² 2p⁶ 3s² 3p³
S electron config= 1s² 2s² 2p⁶ 3s² 3p⁴

S has lower ionisation energy than P as there is a doubly occupied 3p orbital, experiences electron-electron repulsion which increases overall energy, decreasing ionisation energy. P has more stable, half filled 3p orbital with all electrons unpaired.

35
Q

How can you use IE to work out which group an element is in?

A

Have to know IE for removal of each electron

Find biggest jump between IE’s, number of electrons before the jump= group number.

 1st       2nd    3rd    4th    5th Eg- 1000, 1500. 2000, 8000, 9000

8000-9000 is biggest jump, 3 electrons before so element is in group 3!

36
Q

Why does 1st electron shell have less energy than 2nd shell?

A

The electrons in the 1st shell are closer to the nucleus.

37
Q

How many electrons can each energy level hold?

A

e- = 2n² (n= energy level number)

1st shell = 2 electrons
2nd shell= 8 electrons
3rd shell= 18 electrons
4th shell= 32 electrons

38
Q

What is the definition of a sub-level?

A

Made up of orbitals- each orbital can hold up to 2 electrons.

39
Q

How many electrons can each sub shell hold?

A

s=2 electrons
p=6 electrons
d=10 electrons
f=14 electrons

40
Q

What order do the electrons fill in?

A

1s (move from right-left!)
2s 2p
3s 3p 3d
4s 4p 4d 4f (4s before 3d!!)
5s 5p 5d 5f
6s 6p 6d
7s 7p

41
Q

Why does 4s fill before 3d?

A

4s orbitals have a lower energy than 3d orbitals.

Electrons are also removed from 4s orbital before 3d orbital.

42
Q

General electron configuration rules?

A

1) Lowest energy orbital filled first
2) Electrons remain unpaired if possible
3) Electrons must have opposite spins in same orbital
4) Orbitals cannot hold more than 2 electrons

43
Q

What are the exceptions to the electron configuration rules?

A

Chromium- 1s² 2s² 2p⁶ 3s² 3p⁶ 4s¹ 3d⁵
-One of 4s electrons is promoted to 3d so there are 6 unpaired electrons and therefore a lower overall repulsion= more stable.
Copper- 1s² 2s² 2p⁶ 3s² 3p⁶ 4s¹ 3d¹⁰
-One of 4s electrons promoted to 3d so there is a full 3d subshell= more stable.

44
Q

How do we shorten the electronic configuration?

A

Move left and up the periodic table to see which noble gas is behind the element.

Eg- Al=1s² 2s² 2p⁶ 3s² 3p¹
[Ne]3s² 3p¹

Ne has most of the same electronic configuration- add the rest onto the end.

45
Q

How do we know which block an element is in?

A

The outer electron of an element will tell us which block it is in.

Eg- outer electron of Li is in 2s¹: Li is in s block.

s block= G1, G2
p block= G3—>G8
d block= transition elements

Chemistry A Level AQA (11 decks)

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