Test 1 (Atomic History - Periodic Trends)

Question 1

Name three of Dalton’s Postulates of the Atomic Theory

Answer 1

1. Each element is composed of extremely small particles called atoms (they are indivisible. All atoms of a given element are identical)
2. Atoms of an element cannot be converted to entirerent types of atoms by chemical reactions
3. Compounds are formed when atoms pf different elements combine in a simple numerical ratio.

Question 2

How did Thomson find the charge-to-mass ratio?

Answer 2

He constructed a cathode ray tube to measure the effects of electric and magnetic fields on a thin stream of electrons passing through a positively charged electrode. By controlling the strength of the external electrical and magnetic fields, the two fields could be counterbalanced such that the ray passes through the fields undeflected as when no fields at all were imposed. By knowing the strength of those fields he was able to determine the charge-to-mass ratio of those cathode rays/particles

Question 3

What is the charge-to-mass ratio

Answer 3

1.76*10^8 C/g

Question 4

What did Thomson discover?

Answer 4

The charge-to-mass ratio

Question 5

What did Millikan do?

Answer 5

He succeeded to measure the charge of an electrons

Question 6

How did Millikan discover the charge of the electrons?

Answer 6

He observed the movement of tiny droplets of oil in an apparatus containing electrically charged plates and an x-ray source. The x-rays knocked the gas molecules in the air, and as an oil droplet fell through a hole in the positive upper plate, the electrons stuck to the drop, giving it a negative charge. With an electric field off, the mass of the droplet was measure from the rate of its fall. By turning on the e-field and varying its strength, the droplet could be made to fall more slowly, rise or even pause suspended. From this data the total charge was calculated.

Question 7

What did Rutherford discover?

Answer 7

The nucleus

Question 8

What is the gold foil experiment?

Answer 8

A beam of positively charged alpha particles is aimed at a very thin gold foil. A fluorescent screen with ZnS detects the particles passing through or deflected by the foil. Based on Thomson’s plum pudding model, little or no deflections of alpha particles should occur. But the experiment showed that very few alpha particles were deflected at all. This showed that atoms appear to be mostly empty space. Results also showed that the alpha particles that were repelled must have been by a small dense and positive mass within the gold atoms. In order for the alpha particles to rebound, the center of the positive charge must be very large and dense. This is how Rutherford calculated that the atom is mostly empty space but in the center their is the nucleus.

Question 9

Who discovered the neutron?

Answer 9

James Chadwick

Question 10

How was the neutron discovered?

Answer 10

Chadwick detected the neutral particles by having them knock protons out of atoms and then detecting the neutrons.

Question 11

Whats an isotope?

Answer 11

Atoms of a given element that have a different number of neutrons than protons, therefore have different mass numbers.

Question 12

What did Bohr propose about electrons?

Answer 12

They have very specific amounts of energy (quantized)

Question 13

How does an electron move from a lower n value to a higher n value?

Answer 13

The electron must gain energy. It does this my absorbing a photon.

Question 14

How does an electron move from a higher n value to a lower n value?

Answer 14

The electron must lose energy. It does this by emitting a photon.

Question 15

What did De Broglie predict?

Answer 15

That the wavelength of a particle is inversely proportional to its momentum.

Question 16

What is an orbital?

Answer 16

A region of probability where the electron is likely to be found.

Question 17

What are the three integer quantum numbers and what are their functions?

Answer 17

n: Principle quantum number
l: Angular momentum quantum number
ml: Magnetic quantum number

Question 18

What is the radial probability distribution function?

Answer 18

It describes how often an electron is found at a given distance away from the nucleus.

Question 19

What is a node?

Answer 19

The empty space between each orbital.

Question 20

How do you calculate the number of radial nodes?

Answer 20

(n-l)-1

Question 21

What is the shape of an s-orbital?

Answer 21

Spherical

Question 22

What is the shape of a p-orbital?

Answer 22

Like two balloons tied at the knot

Question 23

What is the shape of a d-orbital?

Answer 23

Like 4 balloons tied at the knot

Question 24

What is the shape of an f-orbital?

Answer 24

Like 8 balloons tied at the knot

Question 25

What is Effective Nuclear Charge?

Answer 25

Is the charge of the nucleus that is felt by an electron when shielding is considered.

Question 26

What is shielding?

Answer 26

The effect which reduces attractive forces. (Electrons at different energy levels don’t feel as large of a charge because the lower level electrons are shielding them from the nucleus)

Question 27

What is penetration?

Answer 27

The farther an electron is, the more it wants to movie its way closer to the nucleus.

Question 28

What is electron configuration?

Answer 28

A representation of which orbitals are filled by electrons in an atom. It contains information about the location of every electron in an atom.

Question 29

What is the Aufbau principle?

Answer 29

Electrons are added one by one to the lowest energy orbitals

Question 30

What is Pauli Exclusion principle

Answer 30

No 2 electrons have the same quantum numbers in an atom.

Question 31

What is Hund’s Rule?

Answer 31

For a set of degenerate orbitals, one electron is added to each orbital before they are paired off.

Question 32

How does the size of the atomic radii differ through the periodic table?

Answer 32

Increases going down a group and decreases across a period

Question 33

How does the size of the ionic radii differ?

Answer 33

When an atom is negatively charged, it is larger than its neutral counterpart. When an atom is positively charged, it is smaller than its neutral counterpart

Question 34

What is ionization energy?

Answer 34

The ease with which an electron can be removed. It is the minimum energy required to remove an electron from gaseous atom in the ground state

Question 35

What is the periodic trend of ionization energy?

Answer 35

Decreases going down a group and increases across a period

Question 36

What is electron affinity?

Answer 36

The energy change that occurs when an electron is added to a gaseous atom.

Question 37

What does electron affinity measure?

Answer 37

The attraction of the atom for the added electron. The greater the attraction between a given atoms and an added electron, the move negative the electrons affinity will be.

Question 38

What is paramagnetism?

Answer 38

E-configs that result in unpaired electrons. This means that the atom or ion will have a net magnetic field.

Question 39

What is diamagnetism?

Answer 39

E-configs that result in all paired electrons. This means that the atom or ion will have no magnetic field.

Question 40

How does Zeff affect atomic size?

Answer 40

As you go across a period atomic size decreases. This is because more protons are being added. Electrons are also being added but they are they all in the same shell therefore the shielding doesn’t increase. Since the shielding is constant but the nucleus is gaining charge, Zeff is increasing and with an increased Zeff electrons will be pulled closer to the nucleus making the atom size smaller.

Question 41

How does Zeff affect ionisation energy?

Answer 41

Ionisation energy has to do with the amount of energy that is required to remove an electron from an atom. If Zeff is higher, electrons will be more attracted to the nucleus therefore it will be harder to remove them thus increasing ionisation energy

Question 42

Why does a positive ion that is isoelectric with a noble gas have a higher ionization energy that the noble gas?

Answer 42

Since the two atoms are isoelectric, it means that they have the same number of electrons. Although since the ion is positive, it means that it has one extra proton. This extra proton increases the Zeff therefore it will require more energy to remove an electron since it will be more attracted to the nucleus

Question 43

What is the trend of Zeff on the periodic table?

Answer 43

As you go across the period Zeff increases because protons are being added but shielding is not increasing. As you go down a group Zeff is decreasing because more shells are being added as you go down therefore there is more shielding.