Download Chapter 4 Structure of the Atom An atom is the smallest particle of an

Chapter 4 Structure of the Atom
An atom is the smallest particle of an element that
retains all the properties of that element. 3 parts:
Proton –
Neutron –
Electron –
Every element has certain descriptive properties.
Atomic number –
Atomic mass - this is the number of __________
and __________ in the atom. Measured in atomic
mass units (amu). (To figure the number of
neutrons, subtract atomic number from atomic
mass.)
Symbol and Name - Name (duh). Symbol: first
letter is always capitalized, and the second letter is
always lower case.
Atomic Mass is an average of the masses of all the
isotopes. An ___________ is an element with a
different number of neutrons. Protons must stay
the same, but the # of neutrons can change.
An ion is an _____________________________.
Ions can be either ___________ or __________.
A positive ion has fewer electrons than protons.
A negative ion has more electrons than protons.
All matter can be classified as either an
___________ or a ________________.
An element is the
A compound is
Smallest piece of a compound is a _____________.
A molecule is an electrically neutral group of atoms
that act as a single unit.
The molecular mass of a compound
Subscripts mean that there are more than one of
that atom. Multiply the atomic mass by the
subscript.
Gram atomic mass: the amount of an element that
has a mass in grams equal to its atomic mass.
Gram molecular mass: the amount of a compound
that has a mass in grams equal to its formula mass.
Ex. H2O, CH4
History of the Atom & Atomic Theory
Democritus is the first person to define an atom.
Greek philosopher 2000 years ago. Atom is so small
and indestructible that it cannot be divided up into
anything smaller. Atom means indivisible in Greek.
Law of conservation of mass –
Law of definite proportions:
Law of multiple proportions: In the case where a
pair of elements can form two or more compounds,
the masses of one element combine with a fixed
mass of the other element to form simple, whole
number ratios.
John Dalton came up with these laws in 1803. He
later proposed the first modern ___________
_____________with 4 points.
1. All elements are composed of atoms, which are
____________ and _______________ particles.
2. All atoms of the same element are __________
__________; in particular, they all have the same
_________.
3. Atoms of different elements are ____________;
in particular, they have different masses.
4. Compounds are formed by the joining of atoms of
two or more elements. In any compound, the atoms
of the different elements in the compound are
joined in a definite whole-number ratio.
Takes care of the three laws we looked at.
3 Problems with his theory
1. Atoms are not ___________________. Made of
smaller particles.
2. Atoms can be changed from one element to another,
but not by chemical reactions. Changing one atom
into another is called _________________ and
occurs during radioactive decay.
3. Atoms of the same element are not _______
exactly alike. (can have different masses – these
are called ______________.