SA#2 SCIENCE- CHEMICAL BONDING

Each block on the periodic table includes

Each block on the periodic table includes

basic properties of each element, such as the element's state of matter at room temperature and its atomic number.

Atomic number is

is the number of protons in each atom of the element. Each block also lists an element's atomic mass or the average mass of all different isotopes of that element.

Elements are organized

Elements are organized in periods (rows) and groups (columns). The periodic: table lists elements in order of atomic number.

The atomic number

increases from left to right as you move across a period. Elements in each group have similar chemical properties and react with other elements in similar ways. In this lesson, you will read more about how an element's position on the periodic table can be used to predict its properties.

Dry ice and table salt

re two common substances that are very much different from each other. Analyzing closely, dry ice is chemically carbon dioxide (CO2). It is made up of one carbon atom covalently bonded with 2 oxygen atoms. Also, carbon dioxide is a poisonous colorless gas. Dry ice is the solid form of carbon dioxide. Table salt is sodium chloride (NaCI) made up of one sodium atom and one chloride atom combined by an ionic bond. NaCl is a white crystalline edible solid with very high melting and boiling points. We can see that NaCl and CO2, differ in many ways physically and chemically. In this lesson, we will explore why compounds differ in terms of their chemical structures.

The physical and chemical properties of compounds differ

not only because of their composition but also of the type of bonding of each of the atoms in the compounds

The bonding force between atoms is the electrostatic force of attraction between the negative valence electron

and the positive charge proton in the nucleus of any one of the bonding atoms.

Forces between molecule

intramolecular

forces between molecules

intermolecular forces. These forces determine the kind of chemical bond whether strong or weak bonds.

The periodic taable

has more than 100 blocks-one for each known element.

Intramolecular forces

are usually strong than intermolecular forces. These forces hold atoms together. The stronger the forces are, the harder the substances. The crystalline structure of the substance is formed because of its intramolecular forces. One type of these intramolecular forces also determine the conductivity and luster of a substance.

Intermolecular

are the forces that hold molecules together. This determines some physical properties like melting and boling points of a substance. Chemical bonds are either strong bonds or weak bonds. Strong chemical bonds are the intramolecular forces among the atoms in a molecule. A strong chemical bond is formed either by the transfer or sharing of electrons between atoms.

The type of strong bond

s due to the difference in electronegativity of the involved elements.

Electronegativity is the tendency of an atom to attract electrons.

High electronegativity difference means the stronger its force of attraction of electrons. The electronegativity of an element can be found in some periodic tables. Some types of strong chemical bonds are ionic, covalent, and metallic bonds.

ionization and electronegativity

up and to the right

mettalic character

leftwards down vice versa for non

atomic radius

down and to the left

electron affinity

up and to the right

In 1916 american chemist named

Gilbert Lewis developed a method to show an element's valence electrons. He devel- oped the electron dot diagram, a model that represents valence elctrons in an atom as dots around the element's chemical symbol

Electron dot diagrams

an help you predict how an atom will bond with other atoms. Dots, representing valence electrons, are placed one-by-one on each side of an element's chemical symbol until all the dots are used. Some dots will be paired up, others will not.

The number of unpaired

dots is often the number of bonds an atom can form.

Recall that each element in a group has the same number of valence electrons. As a result, every element in a group has the same number of dots in its electron dot diagram.

Full valence

here are no unpaired dots. Atoms with eight valence electrons do not easily react with other atoms. They are chemically stable. Atoms that have between one and seven valence electrons are reactive, o

Noble atomss

he elements in Group 18 are called noble gases. With the exception of helium, noble gases have eight valence electrons and are chemically stable, Chemically stable atoms do not easily react, or form bonds, with other atoms. Notice that all dots are paired in the dot diagrams of these atoms.

During chemical reactions

elements combine, rearrange or, break apart with others to form new substancess

New substances are created when

chemical bondss are broken or created

Compounds

are more than one kind of element joined together

Octet

describes how chemical bonds happen.

Atoms want a full valence or outer energy. Full valence=8

octet rule

to reach full valence, some atoms want to lose electrons and otherss want to gain electrons

Atoms

fewer tah 4 valence electrons will bond by losing those electrons. THese atomss will become positively charged

atoms with 4 valence electrons

can gain or lose. It depends on the element to which it is bonding

Atoms with more than 4 valence electrons

will bond by gaining electrons up to eight. These will become negatively charged

Valence electrons determine

on element's chemistry. Lewis dot symbols represent the valence electronss of an atom as dots arranged around the atomic symbol. Most useful for main-group elements

Lewis dot symbols

when atoms form compounds, it is their valence electron that actually interact. A lewis dot symbol consists of the element's symbol by dots. Each dot represents a valence electron

for example:

1s22s22p1

since we have 2s2 and 2p1=3 valence electronss

Lewis

dots are not paired until absolutely necessry.

For main group metals such as NA, the number of dots is the number of electrons that are lost

the number of dots is the number of electrons that are lost

For non metals in the second period

the number of unpaired dots is th number of bonds the atom can form

valence electrons for electrons

can be determined based on the elements position o the periodic table

For non metalss second period

number of unpaired dots is the number of bonds the atom can form

valence electrons for elements

Recall that the valence electrons for the elements can be

determined based on the elements position on the periodic table.

valence electrons an number of bonds

number of bonds elements prefers depending on the number of valence electrons In general/