2. Target Objective:
• Explain the formulation of ionic and covalent compound;
• Recognize different types of compounds ionic or covalent from their
properties such as melting point, hardness, polarity, and electrical
and thermal conductivity;
• Explains properties of metal in terms of structure;
• Explain how ion are formed, and;
• Perform the project-based task.
4. THE OCTATE RULE
In 1904, Richard Abegg formulated what is now known as
Abegg's rule, which states that the difference between the
maximum positive and negative valences of an element is
frequently eight.
This rule was used later in 1916 when Gilbert N. Lewis
formulated the "octet rule" in his cubical atom theory. Atoms
will react to get in the most stable state possible. A complete
octet is very stable because all orbitals will be full.
5. OCTET RULE:
• refers to the tendency of atoms to prefer to have eight electrons in
the valence shell. When atoms have fewer than eight electrons, they
tend to react and form more stable compounds. When discussing the
octet rule, we do not consider d or f electrons. Only the s and p
electrons are involved in the octet rule, making it useful for the main
group elements (elements not in the transition metal or inner-
transition metal blocks); an octet in these atoms corresponds to an
electron configurations ending with s2p6s2p6.
• A stable arrangement is attended when the atom is surrounded by
eight electrons. This octet can be made up by own electrons and
some electrons which are shared.
6. Take Note:
The noble gases rarely form compounds. They have the most
stable configuration (full octet, no charge), so they have no
reason to react and change their configuration. All other
elements attempt to gain, lose, or share electrons to achieve a
noble gas configuration.
Example 1: NaCl ( Salt ) The formula for table salt is NaCl. It is the result
of Na+ ions and Cl- ions bonding together. If sodium metal and chlorine
gas mix under the right conditions, they will form salt. The sodium
loses an electron, and the chlorine gains that electron.
8. VALENCE ELECTRONS
Electron configuration refers to the distribution of electrons at
different positions in an atom. It becomes complex as you move
along in the periodic table and therefore, an increase of energy
level of atoms.
Valance electrons are the electrons occupying the highest energy
level in atom. Sometimes called the outermost electrons, the
valance electrons are the ones actually involved in the chemical
bonding and not the electrons closest to the nucleus.
• The elements in the Group 8A of the periodic table elements such as Ne,
Ar, Kr, Xe and Rn have 8 valance electrons; thus they are called the
noble gases, with exception of Helium ( he ) which has only 2 valance
electrons.
9.
10. • VALENCE ELECTRONS
• Let us look at the electron configuration and
distribution of the noble gases: 10 Ne – 1s2 2s2 2p6
• 18Ar - 1s2 2s2 2p6 3s2 3p6
• 36 Kr - 1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p6
• 54Xe - 1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p6 5s2 4d10
5p6
• 86Rn - 1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p6 5s2 4d10
5p6 6s2 4f14 5d10 6p6
11. LEWIS ELECTRON DOT ( LED )
A system known as LEDS, proposed by Gilbert N.
Lewis, is used to emphasize the atoms valence
electrons. It is a short hand method which consists of a
symbol of elements surrounded by dots. The symbol
represents the nucleus of the atom; while the dots
represents the valence electrons of the atom.
12. How to draw the LEDS? The following instructions will guide you. Let us
use CARBON atom as an example:
• Step 1 - Write the chemical symbol of the atom.
( Carbon chemical is C )
• Step 2 – Determine the column or group where an atom belongs in the
periodic table or write down its electron configuration to find out the atoms
number valance electrons. For representatives elements, the number of
valance electrons is the same as the atoms group number or column.
Carbon, a representative elements belong to Group A4; therefore its number of
valance electron is 4.
Carbon with 6 electrons has configuration of 1s2 2s2 2p2. Ths reveals that carbon
has 4 valance electrons.
• Step 3 – Draw the dots that will corresponds to the number of atoms valance
electrons. Distribute the dots evenly, where it may above or below or eitheir side
of the chemical symbol.
13. IONIC CHARGES
• Compounds
- is different both in its physical and chemical aspects from the original atom or element to which it come from.
- forming new substance
• chemical bond
- The compound are bound together by a strong attractive force
• ionic bond
- A type of chemical bond formed when there is a transfer of electrons from one atom to another atom
- this type of bond involves the gaining and losing of electrons.
• Ion
- atom become charged particle
• Cation
- An atom that loses electron becomes positively charged ion
• Anion
- one that gains electron become negatively charged ion
14. EXAMPLES
Na atom
2, 8, 1
No. of proton = 11
No. of electron = 11
Charge = 0
Na ion
2, 8, 1 ( 1 electron is given away )
No. of proton = 11
No. of electron = 11
Charge = + 1
Cl atom
2, 8, 7
No. of proton = 17
No. of electron = 17
Charge = 0
Cl atom
2, 8, 7
No. of proton = 17
No. of electron = 18
Charge = -1
15. FORMATION OF IONIC COMPOUNDS
Ionic bond formation always involves a bonding between a metal and a
non metal.
16. CHEMICAL FORMULAS AND NAME OF IONIC
COMPOUNDS
Ionic compound are compounds composed of ions or
charged particles. They are generally solid at room
temperature and have boiling and melting points. Ionic
compounds are poor conductors or electricity but when
dissolved in water, these compound conducts electricity
since ions are free to move and carry the charge.
17. WRITING CHEMICAL FORMULA
A chemical formula is shorthand method in writing the
name of the compound. It shows symbols to represents
the elements and a subscript to represent the exact
number of atoms used:
18. To write the chemical formula of compound, consider the following steps:
1. Write the symbol of the cat ion first followed by an ion.
2. Write down the ion’s respective charges.
3. Put them together using the crisscross method. The crisscross method is
done by writing the charge value of the first ion as subscript of the second ion
and vice versa. Drop the positive and negative signs.
4. Lastly, reduce the subscript when possible to the greatest common factor.
An understood value of 1 is given if no number accompanies the charge
symbol and this could not be written anymore as subscript during the
crisscross. In here, you need to take note that the total positive charge must be
equal to the amount of negative charge.
19. Example:
Same is done with the following compounds:
Mg+2 + Br = MgBr2
Ca+2 + F = CaF2
20. •Binary Compounds
-involve only two elements
•Ternary Compounds
-compounds that contains three different elements
-Most of these compound consist of metallic cation and
polyatomic anion. To write the formula or ternary compounds,
the crisscross method used in binary compound can also used.
22. NAMING BINARY AND TERNARY COMPOUNDS
Naming binary and ternary compounds is so simple. For binary
compounds, you should name the cat ion first ( specify the
charge if many ). Then name the an ion changing its suffix to –
ide. Thus, NaCl is named as sodium chloride, and MgBr2 is
named magnesium Bromide; while CuBr2 is named as copper
( III ) bromide, and SnCl2, named as Tin ( II ) chloride.
The last two underlined example were named using the stock
system. The system uses the Roman numeral to describe ions
charge. It is enclosed in parenthesis and place immediately
after the metal.
26. LESSON 2: COVALENT BOND
Unlike ionic bond, elements involved in covalent bonds
do not transfer electrons but instead they share
electrons. This type of bond exists between non- metals.
27. FORMATION OF COVALENT COMPOUNDS
• When two or more non-metallic elements combine in a
covalent bonding, a molecule is formed. Gases like O₂,
H₂, N₂, F₂, Cl₂, Br₂, and I₂. Always occur as diatomic
molecule. As such, they are more stable than single
atoms.
28. To show how the sharing of electrons in a covalent
bonding happens, let us take example oxygen. Oxygen
has 8 electrons with a configuration of 1s2, 2s2, 2p4. I t
has valance electrons of 6. Therefore, to be in stable
state and to satisfy the octet rule ( states the atoms tend
to gain , lose or share electrons to attain 8 valance
electrons ) it needs two more electrons. The two oxygen
will share two electrons from each other to attain 8
valance electrons.
29. THREE TYPES OF COVALENT BOND
• A single covalent bond , denoted by one short line ( -
), is the sharing of one electron pair between the two
atoms.
• A double covalent bond, denoted by two short lines (
= ), is the sharing of two electrons pairs.
• A triple covalent bond, denoted by three short lines (
=_ ), is the sharing of three electrons pairs.
30.
31.
32.
33. MOLECULAR GEOMETRY
In molecular geometry, the bond lengths and angles are
determined experimentally. A simple procedure known
as the valance shell electron pair ( VSEPR ) can help
us predict the geometric arrangement of atoms in the
molecules. The concept of VSEPR is that all the
valance electron pairs of the central atom considered. It
includes both the pairs that form covalent bond or the
bonding pairs and the pairs that are un shared or non
bonding pairs known as lone pair.
34. DIFFERENT MOLECULAR GEOMETRY
LINEAR
This shaped is produced when two groups try to
get as far away from each other as they can. The
angle between a lone pairs and the central atom
is 180 degrees.
TRIGONAL PLANAR
This shaped is formed when three pairs get as far
apart each other as possible. The angle formed
by any two bonds in molecule 120 degrees.
TETRAHEDRON
This structure is a common one. Many nonmetals
and ion have this structure. The bonds have equal
distance. The bond angle for tetrahedron is 109.5
degrees.
35. TRIGONAL BIPYRAMID
When there are five electron pairs, trigonal
bipyramid structure is formed. Unlike
tetrahedron which bonds are equidistant,
the distance of trigonal bipyramid bonds
are not equal, as evident in the given figure
on the right.
OCTAHEDRON
Six bonding pairs are present in which all
the positions are equivalent, all the bond
distances are equal and all the angles
formed by any adjacent bonds 90 degrees.
38. Direction: Answer the following item in your
SCIENCE NOTEBOOK.
1. Draw the covalent bonds formed in the following
molecules:
a. H₂O b. CCl₄ c. NF₃
2. Name the following covalent compounds:
a. N₂O b. NBr₃ c. As₂O₂
39. LESSON 3: METALLIC BONDS
What Metallic Properties Do Materials Have?
Direction: Answer the following questions in you
SCIENCE NOTEBOOK.
1. List down as many metallic products or materials
that your see around your house.
2. Describe their physical appearance and structure.
3. What characteristic do they have in common?
4. Is the materials lustrous and shiny?
5. Is the materials malleable?
6. Can it be used to conduct heat or electricity?
40. Metallic bond, force that holds atoms together in a metallic
substance. Such a solid consists of closely packed atoms. In
most cases, the outermost electron shell of each of the metal
atoms overlaps with a large number of neighboring atoms. As
a consequence, the valence electrons continually move from
one atom to another and are not associated with any specific
pair of atoms. In short, the valence electrons in metals, unlike
those in covalently bonded substances, are nonlocalized,
capable of wandering relatively freely throughout the entire
crystal. The atoms that the electrons leave behind become
positive ions, and the interaction between such ions and
valence electrons gives rise to the cohesive or binding force
that holds the metallic crystal together.
Editor's Notes
Na 2, 8, 1 ionization energy Na+
( Loses electron )
NaCl
Cl 2, 8, 7 electron affinity Cl
( gains electron )
