CHEM 121 Lecture Notes - Lecture 2: Cathode Ray, Atomic Number, Unified Atomic Mass Unit

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15 Nov 2016

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Law of conservation of mass- mass at the beginning is the same at the end of a reaction. Law of multiple proportions- relates to the ratios of elements in compounds. Dalto(cid:374)"s theor(cid:455)- 4 principles (3rd has been slightly disproven by radioactive atoms) Robert milikan: oil drop work for charge of electron. Radioactivity: alpha, beta, and gamma increased understanding of subatomic particles. J. j. thompson: cathode rays and electrons, 1897: alpha- 2 protons, 2 neutrons= 2+ charge, beta- high energy electron= 1- charge, gamma- pure energy= no charge. Rutherford"s (cid:374)uclear (cid:373)odel a(cid:374)d the gold foil e(cid:454)peri(cid:373)e(cid:374)t. Mass number: number of protons and neutrons (a) Isotopes: atoms with the same atomic number and different numbers of neutrons (different mass number) Scale of atoms: 1 amu= 1. 66 x 10^-24 g, 1g= 6. 02 x 10^23 amu. A systematic catalog of the elements: arranged on order of atomic number.

Related Questions

Predict the charge that an aluminum ion would have.

Terms in this set (26)

example of the law of multiple proportions

Two different compounds formed from carbon and oxygen have the following mass ratios:

1.33 g O: 1 g C and 2.66 g O: 1 g C.

2) Which of the following statements is FALSE according to Dalton's Atomic Theory?

A) Atoms combine in simple whole number ratios to form compounds.

B) All atoms of chlorine have identical properties that distinguish them from other elements.

C) One carbon atom will combine with one oxygen atom to form a molecule of carbon monoxide.

D) Atoms of sodium do not change into another element during chemical reaction with chlorine.

E) An atom of nitrogen can be broken down into smaller particles that will still have the unique properties of nitrogen.

The mass number is equal to

the sum of the number of protons and neutrons

a subatomic particle is

A neutral atom contains the same number of protons and electrons

true statement about isotopes

Some elements have 3 or more naturally occurring isotopes

Identify a cation

An atom that has lost an electron

What species is represented by the following information?

p+ = 12 n° = 14 e- = 10

Mg2+

What species is represented by the following information?

p+ = 47 n° = 62 e- = 46

Ag+

What species is represented by the following information?

p+ = 17 n° = 18 e- = 18

Cl-

Predict the charge that an aluminum ion would have

Predict the charge that a calcium ion would have

Predict the charge that an ion formed from sulfur would have

Predic

tangnu832

Nuclear Decay Equations

Learning Goal:

To predict the products of alpha emission, beta emission, positron emission, and electron capture.

Radioactivity is the spontaneous emission of radiation from an unstable nucleus. There are five major types of radioactive decay:

Alpha (Î±) radiation consists of helium nuclei. The helium nucleus is a small particle containing two protons and two neutrons (42He).

Beta (Î²) radiation consists of electrons. In nuclear equations, the standard format for representing a beta particle using superscripts and subscripts is 0â1e.

Positron emission results from the conversion of a proton in the nucleus to a neutron. The ejected positron is a particle that has the same mass as an electron but an opposite charge. In nuclear equations, the standard format for representing a positron using superscripts and subscripts is 01e .

Electron capture is the capture of an inner shell electron by a proton in the nucleus. The process emits gamma (Î³) radiation and results in a proton converting to a neutron. Gamma radiation consists of high-energy electromagnetic radiation.

Gamma (Î³) radiation consists of high-energy radiation, and contains no particles and thus they have no mass. In nuclear equations, the standard format for representing gamma radiation using superscripts and subscripts is 00Î³.

Balancing a decay equation

There are two main rules to remember when balancing nuclear equations:

The total of the superscripts in the reactants and products must be the same.

The total of the subscripts in the reactants and products must be the same.

For an isotope of an element, the superscripts are mass numbers, and the subcripts are atomic numbers:

Mass number â¶ AAtomic number â¶ Z X âµ Chemical symbol

Where the mass number (A) is the sum of the number of proton and number of neutrons in the nucleus, atomic number (Z) is the number of protons in the nucleus, and chemical symbol (X) is the symbol of the specific element.

Part A

Identify the nuclide produced when americium-241 decays by alpha emission:

241 95Amâ42He + ?

Express your answer as an isotope using prescripts.

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Part B

Identify the nuclide produced when phosphorus-32 decays by beta emission:

3215Pâ 0â1e + ?

Express your answer as an isotope using prescripts.

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Part C

Identify the nuclide produced when fluorine-18 decays by positron emission:

18 9Fâ01e + ?

Express your answer as an isotope using prescripts.

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Part D

Identify the nuclide produced when thallium-201 decays by electron capture:

201 81Tl+ 0â1eâ00Î³ + ?

Express your answer as an isotope using prescripts.

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CHEM 121 Lecture Notes - Lecture 2: Cathode Ray, Atomic Number, Unified Atomic Mass Unit

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Terms in this set (26)