Chapter 2 - Atoms, Ions, and the Periodic Table Flashcards
Law of Conservation of Mass
Mass is not gained or lost in a chemical reaction
Law of Definite Proportions
A compound always has the same mass ratio of the elements that compose it
Dalton’s Atomic Theory
All matter is composed of small, indivisible particles, called atoms. All atoms of a given element are identical both in physical and chemical properties. Atoms are not created or destroyed in chemical reactions. Atoms combine in simple, fixed, whole-number rations to form molecules. In a chemical reaction, atoms rearrange into new combinations, obeying the Law of Conservation of Mass.
Structure of an atom
They are divisible. They are composed of subatomic particles, but they don’t have the same properties as the host.
Nucleus
Dense center of the atom
Protons
Positively charged subatomic particles
Neutrons
Uncharged subatomic particles
Electrons
Negatively charged subatomic particles
1 electron charge
1.592 x 10 ^-19 Coulomb
Who did the Milliken Oil Drop experiment?
The Gold Foil Experiment
By British physicist Ernest Rutherford in 1911. 1) Radioactive sample emits beam of alpha particles 2) Beam of alpha particles strikes gold foil 3) Flashes of light produced when alpha particles strike zinc-sulfide screen show that most alpha particles are transmitted with little or no deflection 4) minor deflections of alpha particles are seen occasionally 5) Major deflections of alpha particles are seen very rarely
Cathode Ray Tubes
British physicist J.J. Thomson in 1897.
Millikan Oil Drop Experiment
In 1909 by American physicist Robert A. Millikan
1 electron charge
1.592 x10^-19 Coulomb
Atomic number
Number of protons in an atom
Atom number, Z
Number of protons in the nucleus of an atom
Mass number, A
Number of protons and neutrons in the nucleus of an element’s atom, A = Z +N
Neutron number, N
Number of neutrons in the nucleus of an element’s atom
Isotope
An atom that contains a specific number of neutrons
Isotopic symbol
A notation that adds the mass number, A, and atomic number, Z, to the elemental symbol, X. A/Z(X)
Cations
Positively charged ions. They have fewer electrons than in the neutral atom, they are named by adding “ion” to the elemental name”.
Anions
Negatively charged ions. They have more electrons than in the neutral atom. They are named by adding “-ide ion” to the suffix of the elemental name.
Atomic mass: AMU scale
1 amu = 1/12 mass of one C-12 atom = 1.6606 x 10^-24 g
Relative atomic mass
The isotopic mass of individual isotopes of an element, taking into account the naturally occurring relative abundance of each isotope.
Relative atomic mass equation
(Isotope Mass of Isotope 1) x (Relative Abundance of Isotope 1) + (Isotope Mass of Isotope 2) x (Relative Abundance of Isotope 2)
Group or Family
Elements in the same column having similar properties, with a roman numeral or arabic number
Period
Horizontal row of elements having properties that tend to vary in a regular fashion, designated by Arabic numbers
Alkali metals
Group 1 (IA) metals (not hydrogen). They are considered reactive because they react readily with other elements and compounds. React with water to produce hydrogen gas
Alkaline earth metals
Group 2 (IIA) metals. More reactive than the transition metals but less reactive than alkali metals
Halogens
Group 17 (VIIA) nonmetals. Exist naturally as diatomic molecules (2 atoms)
Noble gases
Group 18 (VIIIA) nonmetals. Also called inert gases, do not chemically react with other elements under normal conditions
Main-group elements
Contain any element in the eight groups designated with the letter A. In the Arabic numbering, groups 1, 2, and 13-18
Transition metals
Contain any element in the 10 groups designated with the letter B. Arabic numbering, groups 3-12
Inner-transition metals
Contain the lanthanides and actinides listed separately at the bottom of the table
Diatomic molecules
Occur in pairs when not combined with other atoms.
7 elements that exist as diatomic molecules
N2, O2, F2, Cl2, Br2, I2, H2
Metals tend to lose electrons
To become cations, to have the same number of electrons as the last noble gas
Nonmetals tend to gain electrons
To become anions, to have the same number of electrons as the next noble gas
