Chemistry - Atom

neutron

one of three main particles that make up the atom. It is found in the nucleus and is neutral in electric charge. It has about the same mass and diameter as a proton.

proton

one of three main particles that make up the atom. It is found in the nucleus. It has an electrical charge of one +1 and a mass of 1 atomic mass unit (amu). Atoms of any given element have a unique number of protons that is different from the numbers of protons of all other elements.

average atomic mass

the weighted average of the atomic masses of the naturally occurring isotopes of an element

Fission

A nuclear reaction in which a massive nucleus splits into smaller nuclei with the simultaneous release of energy

Fusion

Creation of energy by joining the nuclei of two hydrogen atoms to form helium.

Radiation

Energy that is radiated or transmitted in the form of rays or waves or particles.

Dalton atomic theory

Proposed in 1804 All matter is composed of extremely small particles called atoms. Atoms of a given element are identical in size, mass, and other properties. Atoms of different elements differ in size, mass, and other properties. Atoms cannot be subdivided, created, or destroyed. Atoms of different elements can combine in simple whole number ratios to form chemical compounds. In chemical reactions, atoms are combined, separated, or rearranged

half-life

The time required for one half of the atoms of a radioisotope to emit radiation an decay products

beta particle

a high-speed electron with a 1- charge that is emitted during radioactive decay

alpha particle

a type of nuclear radiation consisting of two protons and two neutrons

gamma radiation

a type of nuclear radiation made of high-energy waves

electrons

are one of three main types of particles that make up the atom. They are extremely small and have an electric charge of -1. All atoms have the same number of electrons as protons.

isotope

atoms of the same element that differ in their numbers of neutrons

atom

comes from the Greek atomos and means "indivisible.

"plum pudding" model

consisted of a uniform sphere of positive charge with negative electrons embedded in the sphere. J.J. Thomson

atomic mass unit

is defined as a mass equal to one twelfth the mass of an atom of carbon-12.

mass number

is its mass in atomic mass units (amu), which is about equal to the total number of protons and neutrons in the atom. The number of neutrons = mass number - atomic number.

nucleus

positively charged center of an atom containing protons and neutrons.

The law of definite proportions

states that a given chemical compound always contains the same elements in the exact same proportions by mass.

The law of conservation of mass

states that matter cannot be created or destroyed.

The law of multiple proportions

states that whenever the same two elements form more than one compound, the different masses of one element that combine with the same mass of the other element are in the ratio of small whole numbers.

atomic number

the number of protons in an atom. This is also unique for each element.