chemistry history

How many neutrons are in the following atom? 235 U 92

143

How many protons are in the following atom? 235 U 92

92

beta particle

An electron or particle similar to an electron emitted from the nucleus with negligible mass and a charge of -1; represented by β-.

ion

Atom or group of atoms with a net charge caused by unequal numbers of electrons and protons.

The discoverer of radioactivity was ________.

Becquerel

The first attempt at publishing a list of relative atomic masses was made by ____________.

Dalton

Who was the first to propose the idea of atoms?

Democritus

quantum

Energy available or given off in specific, predictable quantities.

Describe Thomson's concept of the atom.

He thought they were tiny particles of matter filled with electrons, but the internal structure was positively charged, so it remained neutral. (The plum pudding model: scattered throughout)

alpha particle

Helium nucleus emitted from the nucleus of a decaying isotope; represented by He2+.

gamma ray

High energy ray emitted from some radioactive atoms.

Who is considered the father of atomic theory?

John Dalton

isotope

Members of the same element (same atomic number) but different mass number due to different numbers of neutrons in the nucleus.

electron

Negative subatomic particles; symbolized by e-; located outside the nucleus; in constant motion; 1/1,837 the mass of a proton.

neutron

Neutral particle found in the nucleus; mass nearly equal to that of a proton; neutrons plus protons constitute mass of atom.

proton

One of the particles of the nucleus; positively charged; symbolized by p; assigned a mass value of 1 unit; protons plus neutrons constitute mass of atom.

The discoverer of X-rays was ________.

Roentgen

Which scientist supplied the equations to combine wave and particle theory?

Schrödinger

Nucleus

The central core of the atom containing most of the mass and made up of protons and neutrons.

emission spectrum

The distribution of light when passed through a prism or other device that breaks the light into its individual components.

atomic mass or mass number

The number of protons plus neutrons in the nucleus.

radioactive

Unstable and capable of disintegrating into different elements, producing radiation and energy.

Explain the Law of Multiple Proportions.

When you take a set amount of one element and add it to a variated amount of another element to make different compounds. The ratio of the amount of the varied element will be simplify to a small whole number.

If the following elements were to combine with each other, choose which demonstrates the Law of Multiple Proportions. Select all that apply.

Z:X = 7:1 Y:X = 11:1

What is a "curie"?

a unit of radioactive disintegration

A device made by J. J. Thomson to process and detect electrons is the:

cathode-ray tube

Rutherford's research was primarily involved with:

defining the components of nuclei

A quantum is a unit of:

energy

A gamma ray is a very high speed particle with no charge.

false

Pitchblende is an ore of plutonium.

false

The two elements isolated by the Curies were radium and uranium.

false

Prior to Thomson's discovery, the atom was thought to be indivisible. Explain the significance of Thomson's concept of the electron.

it opened a door to research on subatomic particles, Because it also showed that atoms weren't the smallest thing.

James Chadwick's primary discovery was the ________.

neutrons

Complete the sentence. Select all that apply. The discoveries of Niels Bohr were:

orbits of electrons quantum energy emissions the relationship between outer shell and chemical properties

Two isotopes of the same element will always have the same number of ________.

protons

J. J. Thomson is credited with which discoveries? Select all that apply.

subatomic particles isotopes electrons

Ernest Rutherford is credited with which discoveries? Select all that apply.

the emissions of radioactive elements the proton

An alpha particle is:

the nucleus of helium

Rutherford and Soddy's research involved:

the theory that uranium successively disintegrated to lead

John Dalton used inductive reasoning to develop his theories.

true

Marie Curie named polonium in honor of Poland.

true

The ideas of Democritus were based on inductive reasoning.

true

The mathematics of combining quantum theory with wave motion of atomic particles is known as a quantum _________ motion.

wave mechanics

When do electrons emit energy?

when moving to a lower orbit