### Chapter 18 Review

```This scientist published a detailed atomic
theory in 1808 based on evidence he
gathered through experiments with
gases. His atomic theory laid the
groundwork for later atomic models.
 John Dalton

British physicist Joseph John Thomson
was the first to identify the:
 electron

A common isotope of Carbon has a
mass number of 13. The total number of
protons in the nucleus would be:
6

The ____ is one kind of particle that
makes up the atom and carries a
positive charge. The neutron makes up
for “missing mass” and is found in the
nucleus. The third kind of particle carries
a ____ charge and has almost no mass.
 Proton
 Negative

Atoms with the same atomic number but
different atomic mass are called:
 isotopes

A – Atomic Number
 B – Chemical Symbol
 C – Name of Element
 D – Atomic mass

Fireworks contain different elements in
them for displaying different colors. The
different colors occur because:
 atoms of various elements emit light at
different frequencies

Elements in the same column on the
periodic table have similar chemical
reactivity because:
 they have the same number of valence
shell electrons

How many energy levels are filled in a
krypton atom?
 Four

A – Proton
 B – Neutron
 C – Nucleus
 D – Energy Level
 E -- Electron

****
 A chemical symbol represents the
_______________ of an element.
 Name

How many protons are in the atom of
the element above?
7

A certain atom has 26 protons, 26
electrons, and 30 neutrons. Its mass
number is ____.
 56

Describe where the electrons are in the
atom, where they have the least energy,
and where they have the most energy.
 Electrons go around the nucleus in a
cloud. Energy is lowest close to the
nucleus, and highest away from the
nucleus.


Use the periodic table to find the name,
atomic number, and the average
atomic mass of the following elements:
O, S.
O, oxygen, 8, 15.999
 S, sulfur, 16, 32.066

Who developed the first periodic table?
 Mendeleev

```