Chapter 4: Atoms and Elements
Date:____________
Section 1: Early Ideas about Matter - Notes
Objectives:
 Recognize that all matter is composed of atoms.
 Explain the early ideas that led to the current understanding of the atom.
Atoms and Elements:

Atoms compose ____________________.

The properties of ________________ determine the properties of __________________.

An atom is the ____________________________ identifiable unit of an element.

An element is a substance that ___________________ be broken down into simpler substances.

There are about _______ different elements found in nature, and consequently about ________
different kinds of atoms.
o
Scientists have succeeded in making about ______ synthetic elements (______________
____________).

The exact number of naturally occurring elements is controversial because some elements
previously considered only ______________________ may actually occur in ________________
in very small quantities.
Early Ideas about Matter:

Many ancient scholars believed matter was composed of such things as ____________________
__________________________________________

Many believed matter could be endlessly ____________________ into ____________________
and ______________________ pieces.

__________________________ (460–370 B.C.E.) suggested that if you divide matter into
smaller and smaller pieces, you end up with tiny, ______________________________________.
o

Democritus called these particles “____________________”
o

Everything else is _______________________________.
meaning “_________________________”
Democritus is the first person on record to have postulated that matter is composed of _______.

________________________ (484–322 B.C.) disagreed with Democritus because he did not
believe ______________________ could exist.
o
Believed everything was composed of ________________________________________
___________________________.
Laws Leading to Modern Atomic Theory:


Law of Conservation of Mass:
o
__________________________________ (1743-1794)
o
In a chemical reaction, matter is neither ________________ nor __________________.
_______________________________ (1754-1826): a French chemist who made observations
on the composition of compounds.
o
In 1797, found that the elements composing a compound always occurred in
______________________________________.
o
Law of Definite Proportions:

All samples of a given compound, regardless of their source or how they were
prepared, have the same ________________________ of their constituent
_____________________


Example:
____________________________ (1766-1844): an English chemist who offered convincing
evidence in support of Democritus.
o
In 1804, published his law of __________________________________________.
o
Law of Multiple Proportions:

When two elements (A and B) form two different compounds, the masses of
________________________ that combine with 1 g of ____________________
can be expressed as a ratio of small whole numbers.

Example:
Dalton’s Atomic Theory:

In 1808 (over 2000 years after Democritus) ______________________________ formalized a
theory of atoms that gained broad acceptance.

Dalton’s atomic theory has five parts:
1. Each element is composed of tiny, indestructible particles called _______________.
2. All atoms of a given element have the same ________________ and other
_________________________ that distinguish them from the atoms of other elements.
3. Atoms combine in simple, ____________________________ ratios to form compounds.
4. Atoms cannot be __________________, ________________, or ___________________
5. In ______________________________, atoms are combined, separated, or rearranged.
Check-in:
 Compare and contrast the atomic theories of Democritus and Dalton. Mark an X under each
name if a statement in the table applies to that person’s theory.
Statement
All matter is made of tiny particles.
Matter is made of empty space through which atoms move.
Atoms cannot be divided.
Atoms cannot be created.
Atoms cannot be destroyed.
Different atoms combine in whole-number ratios to form compounds.
Matter is composed of fire, air, water, and earth.
Democritus
Dalton