Ch. 2 - Atoms, Isotopes, and Nuclear Chemistry

Question 1

Who developed the law of conservation of mass?

Answer 1

Antione Lavoisier in 1785

Question 2

What is the law of conservation of mass?

Answer 2

Matter cannot be created of destroyed. The mass of the products equals the mass of the reactants.

Question 3

Who developed the law of constant composition (aka the law of definite proportions)?

Answer 3

Joseph Proust in 1794

Question 4

What is the law of constant composition?

Answer 4

The proportions of the elements in a given chemical compound are fixed.

Question 5

Who developed the modern atomic theory?

Answer 5

John Dalton in 1808

Question 6

What is the modern atomic theory?

Answer 6

1. All matter consists of solid and indivisible atoms..
2. Atoms are indestructible and retain their identity in all chemical reactions..
3. All of the atoms of a given chemical element are identical in mass and in all other properties..
4. Different elements have different kinds of atoms;; these atoms differ in mass from element to element..
5. Compounds consist of elements combined in small whole - number ratios..

Question 7

What is the mass number?

Answer 7

The Mass number (A) is the number of nucleons. It is written on the top left of an element’s symbol.

Question 8

What are nucleons?

Answer 8

Protons and neutrons.

Question 9

What is an atomic number?

Answer 9

An atomic number (Z) is the number of protons. Is is written on the bottom left of the element’s symbol.

Question 10

What are isotopes?

Answer 10

Atoms of the same atomic number with differen’t mass numbers.

Question 11

What is the formula to find the average mass of an element from its isotope masses?

Answer 11

M_av = Σ(% abundance of isotope/100%) x M_isotope

Question 12

What is the formula to calculate % abundance?

Answer 12

% abundance = (# of atoms of isotope / total # of atoms of element) x 100%

Question 13

What is the symbol for a proton?

Answer 13

¹₁p

Question 14

What is the symbol for a neutron?

Answer 14

¹₀n

Question 15

What is the symbol for a beta particle (an electron)?

Answer 15

¹_-1ß

Question 16

What is the symbol for a positron?

Answer 16

¹₁ß

Question 17

What is the symbol for an alpha particle?

Answer 17

⁴₂a or ⁴₂He²⁺

Question 18

What are the seven nuclear reactions?

Answer 18

1. Alpha emission
2. Beta emission
3. Positron emission
4. Electron capture
5. Fission
6. Fusion
7. Bombardment

Question 19

What are the reactants and products of an alpha emission? Is it spontaneous?

Answer 19

1 nucleus produces 1 nucleus and 1 alpha particle spontaneously.

Question 20

What are the reactants and products of a beta emission? Is it spontaneous?

Answer 20

1 nucleus produces 1 nucleus and 1 electron spontaneously.

Question 21

What are the reactants and products of a positron emission? Is it spontaneous?

Answer 21

1 nucleus produces 1 nucleus and 1 positron spontaneously.

Question 22

What are the reactants and products of an electron capture? Is it spontaneous?

Answer 22

1 nucleus and 1 electron produce 1 nucleus spontaneously.

Question 23

What are the reactants and products of fission? Is it spontaneous?

Answer 23

1 nucleus produces 2 nuclei and some neutrons non-spontaneously.

Question 24

What are the reactants and products of fusion? Is it spontaneous?

Answer 24

2 light nuclei produce 1 nucleus and some neutrons either spontaneously or non-spontaneously.

Question 25

What are the reactants and products of bombardment? Is it spontaneous?

Answer 25

2 heavy nuclei produce 1 nucleus and some neutrons non-spontaneously.

Question 26

What are properties of alpha radiation?

Answer 26

Alpha particles are bigger than other forms of radiation and have a +2 charge so it is easliy stoped but can be highly damaging if ingested.

Question 27

What are properties of beta radiation?

Answer 27

Beta particles have a -1 charge and have a stronger penetrating power than alpha radiation that can cause radiation burns and other biological damage.

Question 28

What are properties of gamma radiation?

Answer 28

Gamma radiation is high energy electromagnetic radiation. It has no mass and no charge so it passes right through matter and causes serious biological damage.

Question 29

What are neutrinos?

Answer 29

They are particles with a neutral charge and and a small mass that creates weak interactions with matter. They carry most of the energy generated in many nuclear reactions.

Question 30

What is the absorbed dose?

Answer 30

A measure of the amount of radiation abrosbed by a given mass of tissue. Measured in grays (Gy) where 1 Gy = 1 J/kg.

Question 31

What is the euqivalent dose?

Answer 31

A measure of how much biological damage can be done by the radiation absorbed. (The absorbed dose is multiplied by a radiation weighting factor (W_R) to calculate the dose in gamma rays). It is measured in sieverts (Sv) where 1 Sv = 1 J/kg.

Question 32

If Z = 1-20, what is the ideal N to Z ratio?

Answer 32

N = Z

Question 33

If Z = 20-82, what is the ideal N to Z ratio?

Answer 33

N > Z, up to N = about 1.5 Z

Question 34

If Z is 83+, what is the ideal N to Z ratio?

Answer 34

No stable nuclides exist.

Question 35

What reaction does neuclear binding energy measure?

Answer 35

When individual protons and neutrons come together to make a nucleus.

Question 36

What is the formula to find nuclear binding energy?

Answer 36

ΔE = Δmc² = (m_nuclide - m_nucleons) x c²

Question 37

What is the formula to find nuclear binding energy per nucleon?

Answer 37

E_b = ΔE / A, where A is the mass number

Question 38

As E_b increases, do nuclides become more or less stable?

Answer 38

More stable.

Question 39

What is activity?

Answer 39

Activity (A) is the quantity of atoms decaying over a given time period.

Question 40

What is a Geiger counter?

Answer 40

A device that uses a tube of gas to click when radiation is present and ionizes the gas in the tube.

Question 41

What formula describes how the number of radioactive atoms decreases over time?

Answer 41

N_{2 =} N₁e^{-k Δt}, where N = number of radioactive atoms and can be replaced by activity (A)

OR

ln(A₂) = ln(A₁) -k Δt

Question 42

What is the formula to find half-life?

Answer 42

ln(N₂/N₁) = -k Δt