Chemistry Unit 4
Topic
Elements and the
Periodic Table
1.4
Essential Knowledge
The principal energy levels (n) around the nucleus of an atom identify
the specific regions (distances from the nucleus) where electrons are likely
to be found. Principal energy levels are identified by n=1, 2, 3 . . . with
n=1 closest to the nucleus. As the value of n increases, so does the
distance from the nucleus.
Using the periodic table, the period (row) where an element is found
indicates the number of occupied energy levels for that element. The
energy level of the valence electrons corresponds to the period number
(row) where the element is found.
Each principal energy level is divided into sublevels (s,p,d and f). In a
given energy level, the s sublevel holds up to 2 electrons, and always fills
before the p sublevel, which can hold up to 6 electrons.
Electron configurations indicate the filling order of all of the electrons
in an atom. The coefficients represent the principal energy level, the
letters represent the sublevels and the superscripts represent the
number of electrons in the sublevel.
Compounds and
Bonding
2.4
Study and Practice
Read: Electrons occupy energy levels
within an atom on pages 87 and 88.
An ionic bond is formed when a metal (element from group 1 through
13) transfers electrons to a non-metal (element from groups 15, 16 or
17). This is because metals form positive ions (lose electrons) and nonmetals form negative ions (gain electrons), resulting in a strong attraction
between oppositely charged ions. Formulas for ionic compounds are
written by balancing the ion charges.
A covalent bond is formed when a non-metal shares electrons with
another non-metal. Formulas for covalent molecules can be predicted
from the dot diagrams of the combining elements.
Study How To: Write an electron
configuration on page 99.
Read Electron configurations can be
written in terms of noble gases page 99.
Do Section Review 17, 18 and 19 on
page 99.
Read Section 5-2 What holds a salt
together? Electron transfers pages 154157. Compare a sodium atom with a
sodium ion by looking closely at
Table 5-3.
Write the Electron Dot Diagram for an
element from groups 1,2,13-18.
Write a formula for 3 covalent compounds
and 3 ionic compounds.
Electron dot diagrams for elements show the number of valence
electrons. Elements will transfer or share valence electrons in order to
have eight valence electrons (octet rule).
Kinetic Theory
3.4
Elements form bonds to become more stable. A filled valence
configuration (eight s and p electrons) is very stable.
Potential energy is stored energy. Chemical bonds contain potential
energy.
Read Section 5-1 Why do atoms form
bonds? Answer Section Review
questions 1 – 5 on page 153.
Energy is required to break bonds. Breaking bonds is endothermic.
Energy is released when bonds are formed. Forming bonds is
exothermic.
The Mole and
Stoichiometry
4.4
Chemical Reactions
5.4
Solutions
6.4
Molar masses from the periodic table can be used to calculate the
number of moles in a given mass of an element or compound. This is
because the masses on the periodic table represent the number of grams
in one mole.
Read Moles can be converted to mass
and vice versa on page 138. Study
sample problems 4D and 4E and do
Practice 4D and 4E.
Because matter cannot be created or destroyed, elements must be
conserved in a chemical reaction. There must be the same number of
each kind of atom on both sides of a balanced equation. The only way to
balance a chemical equation is by placing coefficients in front of each
substance until each side has the same number of atoms of each
element.
Read and study Section 7-2 How are
reactions written? Pages 238-241.
Study How To: Write a balanced
chemical equation and Sample
problem 7A. Do practice 7A.
Solutions that contain ions are called electrolytes because they can
conduct an electric current. Therefore, solutions of ionic compounds in
water (aqueous solutions) are electrolytes, because ionic compounds
dissociate as they dissolve. Conductivity is directly related to the
number of ions in the solution.
Read What happens in an aqueous
solution? Conductance on pages 452 –
455, and Ions in solution on pages 456
and 457
Solutions that do not contain ions are called non-electrolytes because they
cannot conduct an electric current.
Experimentation
7.4
Describe and demonstrate safe techniques for lighting and using gas
burners.
An experimental control remains constant during an experiment and is
compared with the variable being tested (DV).
Given an experimental design, identify the variables (IV and DV),
constants and control. Predict the outcome when a variable is changed.
Class Website
http://fcps.blackboard.com
The Chemistry Place
http://www.chemplace.com
Read Techniques 4 and 5 on pages 657
and 658.
Read about Flame Tests on page 686
and Safety on page 687.
Read The Scientific method Involves
Experiments on page 18-19.
User ID: studentehs1
Password: 321
Theme: Naming compounds and physical properties of substances.
Mastery Knowledge 4:
Book References: Addison-Wesley: p. 85-87, 96-105, 304-311, 552-553
1.
The name of an ionic compound is determined by the names of its component ions. The name of the cation comes first,
just as the cation is listed first in the formula. For binary compounds, consisting of two elements, the ending of the anion
is changed to –ide. For example, KI is called potassium iodide, and MgCl 2 is called magnesium chloride. Polyatomic ions
are tightly bonded groups of atoms that behave as a unit and carry a charge. Be able to give the name, formula and
charge for the following polyatomic ions: ammonium (NH4+), hydroxide (OH-), nitrate (NO3-), carbonate (CO32-), sulfate
(SO42-) and phosphate (PO43-).
2.
Naming binary molecular (covalent) compounds is similar to those for naming ionic compounds. However, the names of
molecular compounds include prefixes that indicate the number of atoms in a molecule. Know the first ten numerical
prefixes, that indicate from 1 to 10 atoms: mono-, di-, tri-, tetra-, penta-, hexa-, hepta-, octa-, nona-, and deca-. The
ending suffix –ide is added to the second element of the formula. For example, the formula for carbon dioxide is CO2.
3.
In a metal the atoms are packed together as closely as possible in a regular pattern or lattice. All the atoms share the
valence electrons, so that no electron belongs to any particular atom and they are free to move throughout the metal lattice.
Many the physical properties are due to these mobile valence electrons. Metals are solids at room temperature, lustrous,
malleable, and good conductors of heat and electricity. Alloys are homogeneous mixtures of metals; e.g. brass is a mixture
of copper and zinc. The properties of alloys are different from those of pure metals.
4.
Nonmetals do not possess a metallic luster, are poor conductors of heat and electricity and are brittle. Many nonmetals are
gases at room temperature, some are solids and one (bromine) is a liquid. Nonmetals show quite a variation in physical
properties. Allotropes are nonmetals that have different elemental forms. For example, carbon exists in several forms,
graphite, diamond, and buckminster fullerene (buckyballs).
5.
Metalloids are between the metals and nonmetals on the periodic table. The metalloids may have some properties of
metals and some properties of nonmetals.
6.
Ionic substances exist in a lattice structure (a repeating 3-dimensional pattern) and are electrically neutral. They usually
have high melting points, which indicates that ionic bonding is very strong. Ionic substances are solids at room
temperature, tend to be brittle, and dissolve in water. Aqueous and molten ionic compounds are good conductors of
electricity. As solids, however, ionic compounds do not conduct electricity because the ions are held in position and
cannot move freely. A group of elements that combine to form an ionic compound is called a formula unit.
7.
A group of atoms that are united by covalent bonds is called a molecule. Molecules consist of nonmetals and may contain
as few as 2 atoms or as many as a thousand or even a million atoms. Thus, the properties of molecular substances are quite
varied. They may be solid, liquid or gaseous at room temperature. Molecular substances have relatively low melting
points compared to ionic substances.