Chem Midterm - Chapter 4 Vocabulary

Dalton’s Atomic Theory

Matter is composed of extremely small particles called atoms, atoms are indivisible and indestructible, atoms of a given elements are identical in size, mass, and chemical properties, atoms of a specific element are different from those of another element, different atoms combine in simple whole-number ratios to form compounds, and in a chemical reactions atoms are separated, combined, or rearranged

Nucleus

A tiny, dense region in the center of the atom that contains most of the atom’s positive charge and mass

Proton

A subatomic particle carrying a charge equal to but opposite that of an electron

Neutron

A subatomic particle that has a mass nearly equal to that of a proton, but carries no electric charge

Electron

Negatively charged particles that are part of all forms of matter

Radioactive Decay

Unstable nuclei loses energy by emitting radiation in a spontaneous process

Atomic Number

The number of protons in an atom

Isotope

Atoms with the same number of protons but different number of neutrons

Mass Number

The sum of the atomic number (number of protons) and neutrons in the nucleus

Atomic Mass Unit (amu)

1/12th of the mass of a carbon-12 atom

Atomic Mass

The weighted average of mass of the isotopes of the element

Nuclear Equation

An equation that shows the atomic numbers and mass numbers of the particles involved in radiation or decay