Chapter 11 The Atomic Nature of Matter Flashcards
Atom
The smallest particle of an element that has all of the element’s chemical properties.
Brownian motion
The haphazard movement of tiny particles suspended in gas or liquid resulting from their bombardment by the fast-moving atoms or molecules of the gas or liquid.
Atomic nucleus
The core of an atom, consisting of two basic subatomic particles - protons and neutrons.
Element
A pure substance consisting of only one kind of atom.
Atomic number
The number that designates the identity of an element, which is the number of protons in the nucleus of an atom; in a neutral atom, the atomic number is also the number of electrons in the atom.
The periodic table of the elements
A chart that lists the elements in horizontal rows by their atomic number and in vertical columns by their similar electron arrangements and chemical properties.
Quantum mechanics
The theory of the small-scale world that includes predicted wave properties of matter.
Isotopes
different forms of an atom that contains the same number of protons but different numbers of neutrons.
Atomic mass unit (amu)
The standard unit of atomic mass, which is equal to one-twelfth the mass of the common atom of carbon, arbitrarily given the value of exactly 12. One amu has a mass of 1.661 x 10-24 grams.
Compound
A material in which atoms of different elements are chemically bonded to one another.
Mixture
A substance whose components are mixed together without combining chemically.
Molecule
A group of atoms held together by sharing of electrons. Atoms combine to form molecules.
Antimatter
A “complementary” form of matter composed of antiparticles having the same mass as particles of ordinary matter but being opposite in charge.
Dark matter
Unseen and unidentified matter that is evident by its gravitational pull on stars in the galaxies. Along with dark energy, dark matter constitutes perhaps 90% of the stuff of the universe.
