# Chapter 18 � Properties of Atoms and the Periodic Table by pWh1aG

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```									Chapter 17 – Properties of Atoms and the Periodic Table

Section 1 – Structure of the Atom

Objectives
 Identify names and symbols of common elements.
 Identify quarks as subatomic particles of matter.
 Describe the electron cloud model of the atom.
 Explain how electrons are arranged in an atom.

An abbreviated way to write the name of an element is called a________________ .

Chemical symbols consist of one capital letter or a capital letter plus one or two
small letters. Some of the symbols come from the elements Latin name.p. 506,
Table 1

The symbol for chlorine is_____ .

The idea of atoms began more than 2400 years ago with the Greeks. Atoms consist
of a positively charged center or core that is called the _________ . The nucleus is
surrounded by negatively charged particles called ________ .

The electrons move around the nucleus. The two major kinds of particles in the
nucleus are________ and _________. The mass of a proton is about the same as
that of a neutron. The mass of an electron is very, very small.

Proton         Positive charge(1+)
Electron       Negative charge(1-)
Neutron        No Charge

Protons and neutrons are made of even smaller particles called _____________ .

Right now, we know of 6 different quarks. Each proton and neutron contains 3
quarks.

To bust an atom up into the quarks, a particle accelerator is used. Inside the
particle accelerator, protons are bombarded with other ________ to produce the
quarks.

The particles that result from the collision are detected in a device called a bubble
chamber. P. 508, Figure 3.

One particle accelerator, the _________, is located at Fermilab in Batavia, Illinois.p.
508, Figure 2.
We use models to help us understand something we can’t see directly, usually
because it is too large or small. As more information is collected, scientists change
their models.

Around 400BC, _____________ proposed the idea that atoms make up all
substances. Aristotle disagreed and his theory was accepted for about 2000 years.

In the 1800s, John Dalton came up with an early model of the atom that was a solid
sphere.

In 1904, J.J. Thompson came up with a model where the electrons were embedded
throughout the sphere. It was often called the plum pudding model.

In 1911, Ernest Rutherford proposed that almost all the mass of the atom was in the
positively charged nucleus which was surrounded by electrons.

Niels Bohr (1913) pictured the atom as having a central nucleus with electrons
moving around it in well-defined paths, or orbits.

In 1926, scientists developed a better model of the atom. In this model, the
electrons moved about in a region called an _____________ . This cloud surrounds
the nucleus.

Because an electron’s mass is so small, no one can tell exactly where it is as it
moves in the atom. All anyone can tell you is where it probably is. According to
present atomic theory, the location of an __________ in an atom is best
represented by a probability cloud.
p. 510, Figure 5

Within the electron cloud, electrons are at various distances from the nucleus.
Electrons closest to the nucleus have low energy. Electrons farther away from the
nucleus have higher energy. Each energy level of an atom has a maximum number
of ____________ it can hold.

Energy Level of an Atom          # of Electrons
1                                            2
2                                            8
3                                            18
4                                            32
Section 2 – Masses of Atoms

Objectives
 Compute the atomic mass and mass number of an atom.
 Identify the components isotopes .
 Interpret the average atomic mass of an element.

The mass of an atom is very small. Even using grams to measure them wouldn’t be
small enough. The unit of measurement for atoms is the atomic mass unit (amu). A
proton or neutron has a mass of 1 amu (1.6726 x 10-24 g). The electron’s mass is
so small, it is considered negligible. P. 512, Table 2

The atomic mass is defined as 1/12 the mass of a carbon atom containing 6
protons and 6 neutrons.
The identity of an element is determined by the number of _______________.

The _______________of an atom is the number of protons in its nucleus.

Every atom of the same element has the same number of protons. The number of
electrons in a neutral atom is equal to the number of protons.

The sum of the number of protons and the number of neutrons in an atom is the
________________.

Protons + neutrons=Mass number

# of neutrons= Mass number – Atomic number

Ex.- A certain atom has 26 protons, 26 electrons, and 30 neutrons. Its mass number
________ .

Not all atoms of an element have the same number of neutrons. Atoms of the same
element that have different numbers of neutrons are called _________ .

Ex.- Two isotopes of carbon are Carbon 12 and Carbon 14. These isotopes differ
from one another by 2 _____.

Because of the existence of ____________ , the atomic masses of the elements are
not whole value number.p.515, Figure 8.

Because most elements have more than one isotope, each element is given an
______________. It is the weighted average of the mass numbers of all the
isotopes that occur in nature for a particular element.

Complete the following table. The atomic number of hydrogen is 1.

Name                Atomic         Atomic       # of      # of
Mass           Number       Protons   Neutrons

Hydrogen
1
Hydrogen
2

Hydrogen
3

p. 514 – Applying Science – half-life

Concept Map for Atom
Atom

Electron               Nucleus
Cloud                 Mass Number

Electrons        Protons        Neutrons
Atomic #
Negative charge         Pos. Charge    No charge
Section 3 – The Periodic Table

Objectives
 Explain the composition of the periodic table.
 Use the periodic table to obtain information.
 Explain what the terms metal, nonmetal, and metalloid mean.

The word periodic means repeated in a pattern. An example would be a calendar.

In the late 1800’s, Dimitri Mendeleev searched for a way to organize the elements.
When he arranged all the elements known at the time(62) in order of increasing
atomic ______, he found a pattern. Because the pattern was repeated, it could be
considered periodic. We call this arrangement a ____________ of elements.

Although Mendeleev’s periodic table was good, it needed some changes. In 1913,
Henry G.J. Moseley arranged the elements based on their properties and atomic

In a periodic table, the vertical columns are called __________ or ___________.

Elements in the same group will have the same number of outer energy electrons
and will undergo chemical reactions in similar ways.

The groups are numbered 1-18. Elements in each group have similar properties.
The number of electrons in the outer energy level determine the chemical properties
of the element. These outer electrons are so important that a special way to
represent them has been developed. A ____________ uses the symbol of the
element and dots to represent the electrons in the outer energy level. P. 522, Figure
12 & 13

Ex. :Ne:      The elements in Group 18 are known as noble gases. They have a very
stable electron arrangement (8 electrons in their outer energy level).

Some of the later elements in the periodic table are made by man or are called
__________.

The horizontal rows of elements in the periodic table are called ____________. On
the table, there is a stair-step line. All elements to the left of the line, except
hydrogen, are _______. Most metals have the common properties of being
_______, shiny, and _____conductors of heat and electricity. Metals also have 3 or
less _________ in the outer energy level.

The elements to the right of the stair-step line on the periodic table are classified as
__________.
Most nonmetals are _______ that do not conduct heat and electricity well. They
also have between 4 and 8 __________ in their outermost energy level.

The elements next to the stair-step line are _________ because they have
properties of metals and nonmetals.

The elements in groups 3 through 12 are called __________ elements.

As you move from left to right in a row across the periodic table, metallic properties
____________.

p. 524
Thought Question – Are all the elements throughout the universe the same?

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