Chapter 2 Atoms, Molecules, And Ions Flashcards
Law of Multiple Proportions
When two elements form a series of compounds, the ratios of the masses of the second element that combines with one gram of the first element can always be reduced to whole numbers.
Law of Definite Proportion
A given compound always contains exactly the same proportion of elements by mass.
Theory of Atoms
- Each element is made up of tiny particles called atoms.
- The atoms of a given element are identical; the atoms of different elements are different in some fundamental way.
- Chemical compounds are formed when atoms of different elements combine with each other. A given compound always has the same relative numbers and types of atoms.
- Chemical reactions involve reorganization of the atoms- changes in the way they a rebound together. The atoms themselves are not changed in a chemical reaction.
Atomic Masses (Atomic Weights)
The weighted average mass of the atoms in a naturally occurring element.
Avogadro’s Hypothesis
At the same temperature and pressure, equal volumes of different gases contain the same number of particles.
Cathode-Ray Tubes
Electrical discharges in practically evacuated tubes.
Electron
Negatively charged particles
Charge to Mass Ratio
E/M=-1.76x10^8 C/g
E=electron charge
C=coulombs
M=mass
Plum Pudding Model
Electrons (raisins) are dispersed in a positive charge cloud (pudding).
Mass of an Electron
9.11x10^-31 kg
Radioactivity
Spontaneous emission of radiation by uranium.
Three Types of Radioactive Emission
- γ - gamma rays, high energy “light.”
- β - beta particles, high-speed electron.
- α - alpha particles, 2+ charge.
Nuclear Atom
Atom with a dense center of positive charge (nucleus) with electrons moving around the nucleus at a distance that is large relative to the nuclear radius.
Proton
Positive charge equal in magnitude to the electron’s negative charge.
Neutron
Has the same mass as proton, but has no charge.
Mass and Charge of the Electron, Proton, and Neutron
- Electron -> 9.11x10^-31 kg -> 1-
- Proton -> 1.67x10^-27 kg -> 1+
- Neutron -> 1.67x10^-27 kg -> N/A
Isotopes
Atoms with the same number of protons, but different numbers of neutrons.
Atomic Number
Number of protons.
Mass Number
Total number of protons and neutrons.
Chemical Bond
The forces that hold atoms together in compounds.
Covalent Bond
Atoms form bonds by sharing electrons.
Molecule
A collection of atoms.
Chemical Formula
The symbols for the elements are used to indicate the types of atoms present and subscripts are used to indicate the relative number of atoms.
Structural Formula
Individual bonds are shown, indicated by lines.
Ex: H2O -> H-O-H
Space-Filling Model
Shows the relative sizes of the atoms and orientation in the molecule.
Ball-and-Stick Model
Also represents molecules
Ex: CH4 o
I
o—O—o
I
o
Ion
Atom(s) that has a net positive charge or negative charge.
Cation
A positive ion.
Anion
An ion with a negative charge.
Ionic Bond
Force of attraction between oppositely charged ions.
Ionic Solid (Salt)
Solid consisting of oppositely charge ions.
Polyatomic Ion
Multiple atoms.
Periodic Table
All the known elements.
Metal
Tend to form positive ions.
Nonmetal
Tend to form negative ions. They appear in the upper right-hand corner of the table (except hydrogen).
Group (Family)
Elements in the same (vertical) column have similar chemical properties.
Alkali Metal
Group 1A, highly active, 1+ charge with Nonmetals.
Alkaline Earth Metal
Group 2A, 2+ charge.
Halogens
Group 7A, diatomic, 1- charge.
Noble Gases
Group 8A, monatomic gases.
Period
Rows.
