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Flashcards in Atomic Structure Deck (34)
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1

What is the maximum number of electrons an orbital can contain?

2

2

What happens to the energy level of a 3d shell as soon as an electron enters it?

Before, 3d has higher energy levels than 4s. However as soon as an electron enters 3d, the energy level drops below 4s

3

Why does 4s get filled before 3d?

Because 4s is lower in energy than 3d (until 3d gains an electron and its energy level drops)

4

Why do the orbitals have negative values of energy?

Because that is the amount of energy you must give the electron in order to get rid of an electron from an atom in its gaseous state

5

Define ionisation energy

The energy required to remove 1 mole of electrons from 1 mole of atoms in their gaseous state

6

What are the factors affecting the size of the 1st ionisation energy?

Size of nuclear charge
Distance from the nucleus
Shielding (inner shells block attractive force of nucleus)
Pair repulsion

7

Describe the difference in 1st ionisation energies between Hydrogen and Helium

Helium has a much higher 1st ionisation energy because the nuclear charge has doubled, but the distance from the nucleus and the shielding is the same

8

Describe the difference in 1st ionisation energies between Helium and Lithium

Lithium has a much lower 1st ionisation energy because the electron is coming from a new quantum shell, meaning there is greater shielding and distance from the nucleus

9

Describe the difference in 1st ionisation energies between Lithium and Beryllium

Beryllium has a higher 1st ionisation energy because there is a greater nuclear charge but the shielding and distance from the nucleus is roughly the same

10

Describe the difference in 1st ionisation energies between Beryllium and Boron

Boron has a lower 1st ionisation energy because the electron is coming from a new sub-shell, meaning there is greater shielding and distance from the nucleus

11

Describe the difference in 1st ionisation energies between Boron and Carbon

Carbon has a higher 1st ionisation energy because the nuclear charge is greater but the shielding and distance from the nucleus is roughly the same

12

Describe the difference in 1st ionisation energies between Carbon Nitrogen

Nitrogen has a higher 1st ionisation energy because the nuclear charge is greater but the shielding and distance from the nucleus is roughly the same

13

Describe the difference in 1st ionisation energies between Nitrogen and Oxygen

Oxygen has a lower nuclear charge because there is pair repulsion but the shielding and distance from the nucleus is roughly the same

14

Why do alkali metals appear at the troughs in an atomic number vs ionisation energy graph?

Because they have the minimum nuclear charge for the quantum shell

15

Why do noble gases appear at the peaks in an atomic number vs ionisation energy graph?

Because they have the highest ionisation energy for their quantum shell

16

Why does Helium have the highest 1st ionisation energy?

Because it has the greatest nuclear charge in its quantum shell, and it is the closest to the nucleus

17

Why does 1st ionisation energy decrease as you go down each group?

Because shielding and distance from the nucleus increases

18

What do successive ionisation energies provide evidence for?

Quantum shells

19

What do successive ionisation energies NOT provide evidence for?

Sub-shells

20

What happens to atomic radius as you go across a period and why?

As you go across a period the atomic radius decreases because, as the charge of the nucleus increases, the electrons are more strongly attracted to the nucleus and so they are drawn inwards

21

Why is the 2nd ionisation energy always higher than the 1st?

Because it takes more energy to remove an electron from a positively charged ion than from a neutral atom (because the electrons are attracted to the positively charged nucleus)

22

What is the equation for kinetic energy?

KE = 1/2 mv^2

23

What is the equation for time of flight? (d = length of tube in metres)

t = d/v

24

What is the equation for the mass of an ion?

Atomic mass of isotope in grams
-------------------------------------------------
1000 x 6.022x10^23

25

What is the expression for time of flight using Ar, d, L and E?

Square root of Ar x d^2
----------------
2000 L E

26

What is an expression for time of flight using Ar?

t1^2 Ar1
-------- = --------
t2^2 Ar2

27

In order to obtain a mass spectrum of a gaseous sample of chromium, the sample must first be ionised. Give two reasons why it is necessary to ionise the chromium atoms in the sample

To allow particles to be accelerated
To generate a current in the detector

28

In a mass spectrometer, what is the difference in velocity between heavy ions and light ions?

The velocity of heavy ions is less than the velocity of light ions (because kE = 1/2 mv^2 and kE is equal for all ions)

29

Define Relative Atomic Mass

The mass of an average atom of an element divided by the mass of one 12C atom, multiplied by 12

30

State how the relative molecular mass of a covalent compound is obtained from its mass spectrum

The Mr is equal to the highest m/z value