Download ATOMS: THE BUILDING BLOCKS OF MATTER

ATOMS: THE BUILDING BLOCKS OF MATTER
3-1 The Atom: From Philosophical Idea to Scientific Theory
The transformation of one substance or substances into one or more new substances is a _____________________________
________________________________________________________ - mass is neither destroyed nor created during
ordinary chemical reactions or physical changes
________________________________________________________________ - 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
________________________________________________________________ - 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
______________________________________________
1) all matter is composed of extremely small particles called atoms
2) atoms of a given element are identical in size, mass, and other properties; atoms of different elements
size, mass, and other properties
3) atoms cannot be subdivided, created, or destroyed
4) atoms of different elements combine in simple whole-number ratios to form chemical compounds
5) in chemical reactions, atoms are combined, separated, or rearranged
differ in
Modern theory has somewhat revised Dalton’s atomic theory to read:
1) all matter is composed of atoms
2) atoms of any one element differ in properties from atoms of another element
3-2 The Structure of the Atom
Atoms are composed of several basic types of smaller particles and that the number and arrangement of these particles within an atom
determine that atom’s chemical properties
__________________ - smallest particle of an element that retains the chemical properties of that element
- has two regions:
1) _________________________ - small region located near the center
- contains ________________________, positively
charged particle, and _______________________, neutral
particle
2) ________________________ - surrounds the nucleus
- contains _______________________________, negatively
charged particles
__________________________________________________ include protons, neutrons, and electrons
Cathode ray - particles pass through the tube from the _______________________________, metal disk connected to the negative
terminal of the voltage source, to the _______________________, the metal disk connected to the positive terminal.
1) when current was passed through the cathode-ray tube, the surface of the tube directly opposite the cathode
glowed. Glow caused by a stream of particles, which they called the cathode ray
2) the ray traveled from the cathode to the anode when current was passed
3) when an object was placed between the cathode and anode, it cast a shadow on the glass and it moved from the
cathode toward the anode
4) cathode rays were deflected by a magnetic field away from a negatively charged object
5) hypothesis: particles that compose cathode rays are negatively charged (physicist Joseph John
Thomson); later, they named the negatively charged particles electrons
The electron has a very large charge for its tiny mass (American physicist Robert A. Millikan). Also
confirmed that the electron carries a negative electric charge.
____________________________________________ continued to investigate the atom’s structure:
1) bombarded a thin, gold foil with fast-moving _______________________________________, positively charged
particles,
2) found that 1 out of 8000 rebounded back toward the source because alpha particles must have experienced some
powerful force within the atom.. The source of this force must occupy a very small amount of space because so
few of the total number of alpha particles had been affected by it. The force must be caused by a very densely
packed bundle of matter with a positive electric charge and bundle was called the nucleus.
Composition of atomic nuclei:
1) made up of 2 kinds of particles: ____________________________ and ________________________________
2) protons and electrons must be ___________________________________
3) the __________________________________of protons in a nuclei determines the atom’s identity
4) __________________________________________ - short-range proton-neutron, proton-proton, and neutronneutron forces that hold the particles together
Size of atoms - measured in picometer (pm) - 1pm = 10-12
- example: 1 cm would be a fractional part of 600 miles so 100 pm is of 1 cm
3-3 Counting Atoms
____________________________________________________ - the number of protons in the nucleus of each atom of that
element
- example: in increasing order so H has 1 proton so is #1,
He has 2 protons so is #2
_____________________________________ - atoms of the same element that have different masses
- ___________________________________ - total number of protons and
neutrons in the nucleus of an
isotope
- example: H 3 isotopes has
mass numbers of 1, 2, and 3
respectively
-
the number of _______________________ varies but not the protons in the
nucleus (protons and electrons are equal)
- example: H has 3:
1) protium - 99.985% abundance with 1 proton only
2) deuterium - .015% abundance with 1 proton, 1 neutron
3) tritium - very small amounts, radioactive with 1 proton, 2 neutrons
- identified by:
1) ________________________ - the name with a hyphen then the
number;
- EX: hydrogen-1
2) ________________________ - 235U ; superscript = mass
number; subscript = atomic
number
- find # of neutrons by subtracting atomic number from mass number
- __________________________ - general term for any isotope of any element
- although isotopes have different masses, they do not differ significantly in their chemical behavior
_____________________________________________________ - amu
- 1/12 the mass of a carbon –12 atom
- example: oxygen-16 is 16/12 or 4/3 the mass of carbon12. This is about 15.994915 amu
____________________________________________________________ - weighted average of the atomic masses of the
naturally occurring isotope of an element
- calculate: (% x weight) + (% x weight) . . .
_________________________ - SI unit for amount of substance that contains as many particles as there are atoms in exactly
12 g of carbon-12
___________________________________________________ - number of particles in exactly one mole of a pure substance
- 6.02 x 10 23
___________________________________________ -
mass of one mole of a pure substance
written: ________________________________________(symbol)
is = to ______________________________________________
example: 1 molar mass = 4 g He
calculating conversions of gram/mol: . . . g . . . = 1 mol