AP CHEMISTRY UNIT 1 - than an atom. 2. Cathode Rays: Streams of elect...

AP CHEMISTRY UNIT 1

• Subatomic Particles: Particles such as protons, neutrons, and electrons that are smaller

than an atom.

• Cathode Rays: Streams of electrons that are produced when a high voltage is applied to

electrodes in an evacuated tube.

• Radioactivity: The process in which an unstable atomic nucleus emits charged particles and

energy.

• Nucleus: The very small, very dense positively charged portion of the atom; it is

composed of protons and neutrons.

• Proton: A positively charged subatomic particle found in the nucleus of the atom.
• Neutron: An electrically neutral particle found in the nucleus of an atom; it has

approximately the same mass as a proton.

• Electron: A negatively charged subatomic particle found outside the atomic nucleus; it is a

part of all atoms and has 1/1836 the mass of a proton.

• Electronic Charge: The negative charged carried by an electron; it has a magnitude of

1.602 x 10^-19 C.

• Atomic Mass Unit (amu): A unit based on the value of exactly 12 amu for the mass of an

isotope of carbon that has six protons and six neutrons in the nucleus.

• Angstrom: A common non-SI unit of length denoted Å, that is used to measure atomic

dimensions: 1 Å = 10^-10m.

• Atomic Number: The number of protons in the nucleus of an atom of an element.
• Mass Number: The sum of the number of protons and neutrons in the nucleus of a

particular atom.

• Atomic Weight: The average mass of the atoms of an element in atomic mass units (amu);

it is numerically equal to the mass in grams of one mole of the element.

• Mass Spectrometer: An instrument used to measure the precise masses and relative

amounts of atomic and molecular ions.

• Periodic Table: The arrangement of elements in order of increasing atomic number, with

elements having similar properties placed in vertical columns.

• Period: The row of elements that lie in a horizontal row in the periodic table.
• Group: Elements that are in the same column of the periodic table; elements within the

same group or family exhibit similarities in their chemical behavior.

• Metal: Elements that are usually solids at room temperature, exhibit high elec- trical and

heat conductivity, and appear lustrous.

• Nonmetal: Elements in the upper right corner of the periodic table; nonmetals differ from
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