Atomic structure and the periodic table

Question 1

What is the structure of an atom?

Answer 1

A nucleus consists of protons and neutrons, which have an overall positive charge and is very tiny compared to the size of the whole atom but take up the most mass.

Electrons orbit the nucleus in orbitals (shells) and these take up most of the volume of the atom.

Question 2

define Mass number and where it is on the element symbol
Define atomic number and where it is on the element symbol

Answer 2

Mass number: the sum of protons and Neutrons (top number)
Atomic number: number of protons (bottom number)

Question 3

What is the relative mass of an electron?

Answer 3

1/1840

Question 4

Define isotope

Answer 4

Atoms of the same element but with a different number of neutrons and same number of protons.

Question 5

Why do isotopes have similar chemical properties?

Answer 5

Because they have the same electronic structure

Question 6

Why do Isotopes sometimes have slightly varying physical properties?

Answer 6

Because they have different masses.

Question 7

Define the Relative isotopic mass

Answer 7

The mass of one atom of an isotope compared to one-twelfth of the mass of one atom of carbon-12

Question 8

How do you calculate the relative atomic mass?

Answer 8

                      100

Question 9

define first ionisation energy

Answer 9

the energy takes to remove 1 mole of electron from one mole of an element to form 1 mole of an ion.

Question 10

what three factors affect ionisation energy

Answer 10

Nuclear charge: the more protons in an atom, the more positively charged the nucleus is, and the stronger the attraction.
electron shell: attraction falls rapidly with distance, so if a shell is closer to the nucleus, it will be more strongly attracted to it.
Shielding: The lessening of the pull of the nucleus- the further away the shell is, there’s less shielding, so easier to pull away the electron.

Question 11

Why do ionisation energies decrease down a group?

Answer 11

• elements further down a group have more energy levels
• so electrons are farther away from the nucleus each time
• so they’re less attracted to the nucleus
• the extra inner shells shield the outer electrons from the attraction of the nucleus.

Question 12

How many electrons does the 3rd energy level hold?

Answer 12

18

Question 13

how many electrons do each of the subshells hold?

Answer 13

s- 2
p- 6
d- 10
f- 14

Question 14

state the order of subshells in an atom

Answer 14

1s
2s 2p
3s 3p 3d
4s 4p 4d 4f

Question 15

what is the Aufbau principle

Answer 15

the idea that the lowest energy levels are filled first.

Question 16

define the empirical formula

Answer 16

the simplest whole-number ratio of the atoms present in the element.

Question 17

Define the molecular formula

Answer 17

The actual number of each type of atom in a compound

Question 18

How do you determine the % composition of elements in a compound?

Answer 18

workout the Mr, then do Ar of each element/ Mr x 100

Question 19

How does atomic radius change from:
Across a period
Down a group

Answer 19

Increase
decreases

Question 20

how does nuclear charge change
across a period
down a group

Answer 20

Increases
Increases

Question 21

How does Shielding change
across a period
down a group

Answer 21

stays constant- electrons are being added to the same energy level
Increases

Question 22

why does ionisation energy decrease from group 2-3

Answer 22

Because in group 3, the highest subshell is p, whereas it’s s in group 2. This means that its further away from the nucleus and there is less attraction between the nucleus and electrons, making it easier to remove an electron

Question 23

Why does ionisation energy decrease from group 5-6

Answer 23

Even though electrons are being added, it’s to the same subshell. This means that the repulsion between electrons makes them easier to remove the electron.

Question 24

What are the different stages of mass spectometry? Include which component helps it to take place.

Answer 24

1. Ionisation- electron beam fires high energy electrons
2. Acceleration- negatively charged plates attract positive ions
3. Deflection: electromagnet creates varying EMFs, depending on their mass-to-charge ratio.
4. Detection: collector plate which induces a current and then amplifies it to produce a spectrum.

Question 25

Describe the stages in TOF mass spectrometry

Answer 25

• electric field is used to accelerate ions through the same voltage.
• ions travel at different speeds depending on their mass towards a negatively charged plate.
• They are then detected, and measured for their time of flight- faster= lighter, slower= heavier.

Question 26

Define periodicity

Answer 26

repeating patterns at regular intervals