|
Chapter 18 – 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. 544,
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. 546, Figure 3. One particle accelerator, the _________, is located at
Fermilab in Batavia, Illinois.p. 546, 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. 548, 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 isotopes of common elements. ·
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. 550, 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.553, 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.
p. 552 – Problem Solving
Activity – 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(26) 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 _________
instead of 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. 560, 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. 562 Thought Question – Are all the elements throughout the
universe the same? |