Topic 1 - Atomic Structure and the Periodic Table

Question 1

How much does an electron weigh?

Answer 1

1/1836

Question 2

What is the definition of relative atomic mass?

Answer 2

The weighted mean mass of an atom of an element compared to 1/12th of the mass of an atom of carbon-12

Question 3

What is the definition of relative isotopic mass?

Answer 3

The mass of an atom of an isotope, compared to 1/12th of the mass of an atom of carbon-12

Question 4

What are isotopes?

Answer 4

Atoms of the same element with different numbers of neutrons.

Question 5

What are isotopes?

Answer 5

Atoms of the same element with different numbers of neutrons.

Question 6

Why do isotopes have the same chemical properties?

Answer 6

They have the same configuration of electrons. Electrons determine the chemical properties

Question 7

Why do isotopes have different physical properties?

Answer 7

They have different masses. Physical properties are determined by the mass of an element

Question 8

What is the definition of relative molecular mass/formula mass?

Answer 8

The weighted mean mass of a molecule/formula unit, compared to 1/12th of the mass of an atom of carbon-12.

Question 9

What is an orbital?

Answer 9

The area that an electron moves in. (Orbitals within the same subshell have the same energy.)

Question 10

What is it called when electrons in the same orbitals spin in opposite directions?

Answer 10

Spin-pairing

Question 11

What shape are s-orbitals?

Answer 11

Spherical

Question 12

What shape are p-orbitals?

Answer 12

Dumbbell shaped

Question 13

What are the two rules working out electron configurations?

Answer 13

1. Electrons fill up the lowest energy subshells first.
2. Electrons fill orbitals singly before they start pairing up.

Question 14

In what order to subshells fill?

Answer 14

1s2, 2s2, 2p6, 3s2, 3p6, 4s2, 3d10

Question 15

Chromium (Cr) and copper (Cu) donate one of their 4e electrons to the 3d subshell. Explain why.

Answer 15

They’re more stable with a full or half-full d-subshell.

Question 16

What is electromagnetic radiation?

Answer 16

Energy that’s transmitted as waves, with a spectrum of different frequencies. (As frequency increases, wavelength decreases)

Question 17

How is an emission spectrum made?

Answer 17

1. In their ground state, atoms gave their electrons in their lowest possible energy levels.
2. Electrons absorb energy and move to higher energy levels, further from the nucleus.
3. Electrons release energy by drilling Frim a higher energy level down to a lower energy level. (The energy levels all have certain fixed values - they’re discrete.)
4. The frequencies of light emitted when the electrons drop down appear as coloured lines in a dark background.

Question 18

What do the different sets of lines in emission spectrum represent?

Answer 18

Electrons moving to a different energy level

Question 19

What are the four basic principles of electron shells?

Answer 19

1. Electrons can only exist in fixed orbitals, or shells, and not anywhere in between.
2. Each shell has a fixed energy.
3. When an electron moves between shells electromagnetic radiation is emitted or absorbed.
4. Because the energy of shells is fixed, the radiation will have a fixed frequency.

Question 20

What is the definition of first ionisation energy?

Answer 20

The energy needed to remove 1 electron from each atom in 1 mole of gaseous atoms to form 1 mole of gaseous 1+ ions.

Question 21

Is ionising atoms endothermic or endothermic?

Answer 21

Endothermic

Question 22

What is the equation for the first ionisation of oxygen?

Answer 22

O(g) —) O+(g) + e-

Question 23

How does nuclear charge affect ionisation energy?

Answer 23

More protons in the nucleus, more positively charge, stronger attraction between nucleus and electrons

Question 24

How does atomic radius affect ionisation energy?

Answer 24

Attraction reduces rapidly with distance. Electrons in shells closer to the nucleus more strongly attracted to nucleus.

Question 25

How does shielding affect ionisation energy?

Answer 25

As number of shells between nucleus and outer electrons increases, outer electrons feel less attraction towards the nuclear charge.

Question 26

What does a high ionisation energy mean?

Answer 26

There’s a strong attraction between the electron and the nucleus, so more energy is needed to overcome the attraction and remove the electron.

Question 27

Why do first ionisation energies decrease down a group?

Answer 27

Extra electron shells so larger atomic radii so electrons are further away from the nucleus and more shielding, reduces their attraction and makes them easier to remove. Overrides increasing nuclear charge

Question 28

What is the definition of the second ionisation energy?

Answer 28

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

Question 29

Why do successive ionisation energies increase?

Answer 29

Electrons are being removed from an increasingly positive ion and there’s less repulsion amongst the remaining electrons so they’re more strongly attracted to the nucleus

Question 30

Why do successive ionisation energies increase?

Answer 30

Electrons are being removed from an increasingly positive ion and there’s less repulsion amongst the remaining electrons so they’re more strongly attracted to the nucleus

Question 31

What do the big jumps in ionisation energy show?

Answer 31

A new shell is being broken into - and electrons is being removed from a shell closer to the nucleus

Question 32

Why does atomic radius decrease across a period?

Answer 32

Number of protons increases, positive charge of the nucleus increases so electrons are pulled closer to the nucleus. Extra electrons gained across the period are added to the outer energy level so they don’t provide any extra shielding effect

Question 33

Explain how the drop between first ionisation energies of atoms in group 2 and group 3 shows subshell structure.

Answer 33

Group 3’s outer electron is in a p orbital rather than an s. The p orbital has a slightly higher energy than the s orbital, so the electron is, on average, to be found further from the nucleus. The p orbital has additional shielding provided by the s electrons. Both these factors override the effect of the increased nuclear charge.

Question 34

Explain why there is a drop in first ionisation energies between group 5 and 6 atoms.

Answer 34

Elements with singly filled or full subshells are more stable than those with partially filled subshells.
The shielding is the same and the electron is being removed from an identical orbital.
In group 5, the electron is being removed from a singly-occupied orbital but, in group 6, it is being removed from an orbital containing two electrons. The repulsion between two electrons in an orbital makes electrons easier to remove from shared orbitals

Question 35

What are 4 pieces of evidence for electron shells?

Answer 35

1. Emission spectra
2. Successive ionisation energy
3. Drop between first ionisation energies of group 2 and 3 atoms
4. Drop between first ionisation energies of group 5 and 6 atoms