Properties and Structure of Atoms

Question 1

What is the decrease in atoms radii due to?

Answer 1

Protons (electrostatic attraction increases)

Question 2

What is an isotope?

Answer 2

An atom of an element with the same number of protons, but different number of neutrons.

Question 3

What is an ion?

Answer 3

An element with a different number of electrons.

Question 4

What is a cation?

Answer 4

A positive ion (lost electrons).

Question 5

What is an anion?

Answer 5

A negative ion (gained electrons).

Question 6

What is a polyatomic ion?

Answer 6

Group of atoms that have a charge.

Question 7

How many electrons can each sub shell hold?

Answer 7

S = 2
P = 6
D = 10
F = 14

Question 8

Who developed the idea of protons?

Answer 8

Rutherford

Question 9

Who developed the idea of electrons?

Answer 9

Thompson

Question 10

Who developed the idea of neutrons?

Answer 10

Chadwick

Question 11

What is the Bohr model?

Answer 11

The idea that electrons orbit the positive nucleus in shells.

Question 12

What is the octet rule for electron configuration?

Answer 12

Each atom aspires to have 8 electrons in its valence shell.

Question 13

What is the exclusion principle for electron configuration?

Answer 13

No 2 electrons can occupy the same 4 quantum numbers.

Question 14

What is Hund’s rule of maximum multiplicity in electron configuration?

Answer 14

Electrons can occupy orbitals of equal energy one at a time before they pair up with opposite spins.
They can do this because this distribution has lower energy - more stable.

Question 15

What is Aufbau’s principle for electron configuration?

Answer 15

Electrons ought to fill the lowest energy orbitals available first.

Question 16

Draw a table of the subatomic particle properties?

Answer 16

Symbols, charges, mass relative to protons and mass in kilos.

Question 17

Describe atomic number?

Answer 17

The atomic number orders elements on the periodic table based on the number of protons in each element.

Question 18

Describe mass number?

Answer 18

Mass number is the number of protons and neutrons in each element.

Question 19

Explain why magnesium atoms form cation with a 2+ charge, but chlorine atoms form anions with a 1- charge?
(4 marks)

Answer 19

• atoms will often react to achieve a more stable electron arrangement by gaining or losing electrons, forming charged ions.
• magnesium has 2 valence electrons, which it will lose in order to achieve a stable octet, thus forming a cation.
• this results in the formation of a 2+ charge because the magnesium now has 2 more protons than electrons.
• chlorine has 7 valence electrons, so it will obtain one more to achieve a stable octet, forming an overall charge of 1-.

Question 20

Describe how the absorption and emission spectrum of an element are related to electron energy levels, and how it is utilised in AAS?
(6 marks)

Answer 20

• the electrons of an atom are confined to specific energy levels or shells.
• electrons are able to move between these shells by absorbing (to jump outwards to a higher energy level ie. further from the nucleus) or emitting (to fall inwards to a lower energy level ie. closer to the nucleus) particular amounts of energy.
• the amount of energy absorbed or emitted by these electrons as they move between shells corresponds to particular wavelengths/frequencies of light which create the corresponding absorption or emission spectra.
• these spectra are unique for each element, since the energy levels of the electron shells are slightly different for each element.
• in AAS the known absorption spectrum for a particular element is used and light of a corresponding wavelength/frequency is shone through the sample being tested.
• the higher the concentration of the particular element in the sample, the more light it absorbs.

Question 21

Explain how spectra lines are produced?
(3 marks)

Answer 21

• samples of atoms can be heated to an excited state, causing electrons to jump to higher energy levels.
• as the electrons return to lower energy levels it emits a colour of light corresponding to the energy difference between the two levels.
• the colours of light emitted are the spectra lines on the emission spectrum.

Question 22

Why are the number of spectra lines of helium and neon different?
(3 marks)

Answer 22

• they have different numbers of electrons
• and different numbers of energy levels
• the jumps between the energy levels of both elements are different.

Question 23

Would a chloride ion be bigger or smaller than a chlorine atom? Why?
(3 marks)

Answer 23

• chloride ion would be bigger.
• chloride ion has a greater number of electrons than protons as it gained 1 electron.
• this unbalance of charge causes less electrostatic attraction and a bigger atomic radius.

Question 24

What is the formula for relative atomic mass?

Answer 24

(mass 1 x abundance 1) + (mass 2 x abundance 2) / 100

Question 25

What is relative atomic mass?

Answer 25

The weighted average mass of an entire sample of an element.

Question 26

What is relative isotopic mass?

Answer 26

The mass of an individual isotope of each element compared to the carbon-12 standard.

Question 27

What are the order of the procedures in mass spectrometry?

Answer 27

Ionisation, acceleration, deflection, detection.

Question 28

How are the lines in the emission spectrum produced?

Answer 28

Electrons dropping to lower energy levels.

Question 29

Where is the magnetic field in a mass spectrometer located?

Answer 29

Around the bend.

Question 30

What is atomic absorption spectroscopy?

Answer 30

Light being absorbed by matter.

Question 31

What is atomic absorption spectroscopy used for?

Answer 31

To measure the concentration of a particular element in a sample to be analysed.

Question 32

How to tell if an isotope is likely to occur?

Answer 32

You round the atomic mass to the nearest whole number and if its close to the isotope it is more likely to occur.

Question 33

What does the magnetic field in a mass spectrometer do?

Answer 33

Changes the direction of ions.

Question 34

If an ion in a mass spectrometer has a larger mass will it be deflected more or less?

Answer 34

less

Question 35

What is mass spectrometry?

Answer 35

A technique used to measure the mass of atoms or molecules.

Question 36

How is mass spectrometry used in terms of atoms?

Answer 36

It identifies the presence and relative abundance of isotopes in a sample of an element.

Question 37

Explain how electron absorption/emission spectra are related to the electron shells (levels) of an element.
(4 marks)

Answer 37

• electron shells have specific energy levels
• electrons can move between electron shells by absorbing or emitting specific amounts of energy
• these amounts of energy have particular frequencies
• this corresponds to and is visualised by an emission or absorption spectrum.