Chapter 4: Atoms and Elements
 Describe the respective properties and
charges of electrons, neutrons, and
protons.
 Determine the atomic symbol and
atomic number for an element using the
periodic table.

Proton: a positively charged subatomic
particle (p)
 Located in the nucleus
 1 proton has a charge of +1
 Actual Mass = 1.67262 x 10-27 kg
 Relative Mass = 1.0073 atomic mass units (amu)
Elements are defined by their numbers of
protons.
 If an atom had a different number of protons, it
would be a different element.
 The number of protons in the nucleus of an
atom is its atomic number and is given the
symbol Z.

Hydrogen always has 1 proton
 Carbon always has 6 protons
 How many protons are in:

 Argon?
 Plutonium?

Electron: a negatively charged subatomic particle (e-)
 Located in the space surrounding the nucleus
 1 electron has a charge of -1
 Actual Mass = 0.00091 x 10-27 kg
 Relative Mass = 0.00055 amu
▪ About 1/1840 of the mass of a proton (small enough to be
negligible)

In a neutral atom, the number of electrons is
equal to the number of protons.
 Hydrogen has 1 electron
 Carbon has 6 electrons
 How many electrons are in?
 Argon?
 Plutonium?
 Neutron: a subatomic particle that has no
charge (n)
 Located in the nucleus
 Actual Mass = 1.67493 x 10-27 kg
 Relative Mass = 1.0087 atomic mass units
(amu)
 The number of neutrons in an atom can
vary.

Electrical charge is a fundamental property of protons
and electrons.
 Positive and negative electrical charges attract each other.
 Positive–positive and negative–negative charges repel each
other.
 Positive and negative charges cancel each other so that a proton
and an electron, when paired, are charge-neutral.
 Matter normally has a neutral charge
 equal numbers of positive and negative
charges that cancel out
 In an electrical storm, the charge
balance of matter is disturbed.
 The quick rebalancing of charge often
occurs in dramatic ways, such as is seen
in lightning.
 It is the number of protons in the
nucleus of an atom that identifies the
atom as a particular element.

The periodic table of the elements lists all
known elements according to their atomic
numbers.

Most chemical symbols are based on the English
name of the element.
 Hydrogen (H), Carbon (C), Oxygen (O)

Some symbols are based on Latin names.
 Potassium (K) – from the Latin kalium
 Sodium (Na) – from the Latin natrium

Additional elements with symbols based on
their Greek or Latin names include the
following:
 lead (Pb), mercury (Hg), iron (Fe), silver (Ag), tin
(S), copper (Cu)

Early scientists gave newly discovered
elements names that reflected their properties:
 Argon, from the Greek argos, means “inactive.”

Other elements were named after countries:
 Polonium after Poland; Francium after France
 Other elements were named after
scientists.

Curium is named after
Marie Curie, a chemist who
helped discover
radioactivity and also
discovered two new
elements. Curie won two
Nobel Prizes for her work.
 List the atomic symbol and atomic number
for each element.
 Silicon
 Potassium
 Gold
 Antimony