The transformation of a substance or substances into one or more new substances
Law of Conservation of mass
the law that states that mass cannot be created or destroyed in ordinary chemical and physical changes
Law of definite proportions
the fact that a chemical compound contains the same elements in exactly the same proportions by mass regardless of the size of the sample or source of the compound
Law of multiple proportions
if two or more different compounds are composed of the same two elements, then the ratio of the masses of the second element combined with a certain mass of the first element is always a ratio of small whole numbers
Dalton's Atomic theory
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 combine in simple, whole-number ratios to form chemical compounds. In chemical reactions, atoms are combined, separated or rearranged.
Dalton's modern Atomic theory
1. matter is composed of small particles (atoms)
2. elements of the same kind are similar in size, mass, and properties of the elements. those that are different are different in these three things.
atoms of the same element that have different numbers of neutrons
(physics and chemistry) the smallest component of an element having the chemical properties of the element
center of an atom. made up of at least one positive charged particle (dense) small compared to the electron cloud
nuetral particles. contains most mass out of electons and protons
negative charge. contains least amount of mass
protons, neutrons, and electrons
Beam of electrons emitted from a cathode when electricity is passed through an evacuated tube.
Plum pudding model
A (disproven) model of the atom created by Thomson. One that holds that negative electrons were scattered throughout the generally positive atom
positively charged particles with about four times the mass of a hydrogen atom
electrons and atomic number(Z number)
short-range proton-neutron, proton-proton, and neutron-neutron forces hold the nuclear particles together
Atomic mass number equals...
protons + neutrons
the amount of a substance that contains as many particles as there are atoms in exactly 12g of carbon-12
a general term for any isotope of any element
average atomic mass
the weighted average of the atomic masses of the naturally occurring isotopes of an element
6.022 x 10^23. The number of particles in exactly one mole of a pure substance
Atomic mass unit
a unit of mass that describes the mass of an atom or molecule; it is exactly 1/12 of the mass of a carbon atom with mass number 12 (symbol, amu)
the mass in grams of one mole of a substance
A greek thinker who created the particle theory(ATOM)
Created the atomic theory, law of conservatioon of mass, and scientific theory
discovered electron; cathode ray tube; plum pudding model
discovereed the charge of an electron and its role in the atom
Used gold-foil experiment and discovered the atomic nucleus. He found that most of the particles passed through, but a small amount of the alpha particles were deflected, sometimes completely back at him. He had just found the atomic nucleus.
said that electrons orbit the nucleus in specific paths like planets around the sun, the farther away an electron is from the nucleus the more energy it must have. his model atom is still used today, even though it is incorrect
used to measure atoms