CHE 110 Chapter Notes - Chapter 2: Barium Hydroxide, Phosphate, Alkali Metal
7 May 2018
School
Department
Course
Professor
Chapter 2: Atoms, Molecules, and Ions
I. The Atomic Theory
a. J D’ atomic theory
i. Elements are composed of extremely small particles, called atoms.
ii. All atoms of a given element are identical, having the same size, mass,
and chemical properties. The atoms of one element are different from the
atoms of all other elements.
iii. Compounds are composed of atoms of more than one element. In any
compound, the ratios of the numbers of atoms of any two of the elements
present is an either an integer or a simple fraction
iv. Chemical reaction involves only the separation, combination, or
rearrangement of atoms; it does not result in their creation or destruction
b. J ’ law of definite proportions
i. Different samples of the same compound always contain its constituent
elements in the same proportion by mass
c. Law of multiple proportions
i. If two elements can combine to form more than one compound, the masses
of one element that combine with a fixed mass of the other element are in
ratios of small whole numbers
ii. Ex. carbon monoxide = 1 O 1 C = 1:1
iii. Ex. carbon dioxide = 2 O 1 C = 2:1
d. Law of conservation of mass
i. Matter can neither be created nor destroyed
II. The Structure of the Atom
a. The Atom
i. Basic unit of an element that can enter into chemical combination
find more resources at oneclass.com
find more resources at oneclass.com
ii. Made up of even smaller subatomic particles
b. The Electron
i. Negatively charged particles
ii. Extremely small mass
c. Radioactivity
i. Rontgen and X-Rays
1. Noticed cathode rays caused glass/metal to emit unusual rays
ii. Becquerel
1. Studied fluorescent properties of substances
2. Uranium compound exposed to thickly wrapped photographic plates
caused them to darken, even without stimulation of cathode rays
iii. Definition
1. Spontaneous emission of particles and/or radiation
2. Term coined by Marie Curie, student of Becquerel
iv. Radiation
1. Emission/transmission of energy through space in the form of waves
v. Three types of rays
1. Alpha rays
a. Consist of positively charged particles (alpha particles)
b. Deflected by positively charged plate
2. Beta rays
a. Electrons (beta particles)
b. Deflected by negatively charged plate
3. Gamma rays
a. High-energy rays; not affected by magnetic fields
d. The Proton and the Nucleus
i. Nucleus
1. Dense central core within the atom
2. Mass constitutes most of the entire atom but only occupies about
1/1013 of the volume of the atom
a. Large mass, small volume
find more resources at oneclass.com
find more resources at oneclass.com
ii. Proton
1. Positively charged particles in the nucleus
2. The charge of each proton has the same magnitude as that of an
electron
3.
Mass of the proton = 1.67262 x 10
-24 g
iii. Expressing Atomic and Molecular Dimensions
1. SI unit picometer (pm)
1 pm = 1 x 10-12 m
iv. Typical atomic radius = 100 pm
v. Typical atomic nucleus radius = 5 x 10-3 pm
e. The Neutron
i. Electrically neutral particles having a mass greater than protons
ii. R’
1. It was known that hydrogen contains only one atom and helium
contains two atoms
a. Ratio of the mass of a helium atom to that of a hydrogen atom
should be 2:1
2. Helium nucleus has 2 protons and 2 neutrons, but in the hydrogen
nucleus there is only one proton and no neutrons; therefore, the ratio
is 4:1
f.
The 3 fundamental components in the atom are the proton, the neutron,
and the electron.
III. Atomic Number, Mass Number, and Isotopes
a. Atoms can be identified by the number of protons and neutrons they contain
b. Atomic number
i. The number of protons in the nucleus of each atom of an element
ii. Chemical identity of an atom can be determined solely by its atomic number
iii. Ex. atomic number of nitrogen is 7, so each neutral nitrogen has 7 protons
and 7 electrons
c. Mass number
find more resources at oneclass.com
find more resources at oneclass.com
Document Summary
The atomic theory: j(cid:656)(cid:649)(cid:655) d(cid:642)(cid:653)(cid:661)(cid:656)(cid:655)"(cid:660) atomic theory, elements are composed of extremely small particles, called atoms, all atoms of a given element are identical, having the same size, mass, and chemical properties. The atoms of one element are different from the atoms of all other elements: compounds are composed of atoms of more than one element. = atomic number + number of neutrons: number of neutrons = difference between mass number and atomic number, or (a-z, ex. Hcl & co: polyatomic molecules, contain more than two atoms, ex. Na+ or cl: polyatomic ions, contain more than one atom, ex. Chemical formulas: definition, expresses the composition of ionic compounds in terms of chemical symbols, molecular formulas, shows the exact number of atoms of each element in the smallest unit of a substance, ex. Potassium bromide kbr: cation = potassium k, anion = bromine br, charges: -1+1=0, ex.
