IPC 7.DRelate the chemical behavior of an element, including bonding, to its placement on the periodic table.

Elements are made of atoms Atoms contain protons, neutrons and

electrons

Example: Lithium atom

Lithium has:

• 3 protons (red)

•4 neutrons (blue)

•3 electrons (black)

Valence or Outermost Electrons are responsible for an atoms chemical behavior and bonding

How do you know how many valence or outermost electrons an atom has? The periodic table tells us!

The Roman Numerals on the

“A” Groups indicate the

number of outer electrons

Elements are arranged:

Vertically into Groups or Families

Horizontally Into Periods

If you looked at one atom of every element in a group you would see…

They all have the same number of outer or valence electrons

The group IIA atoms all have 2 electrons in their outer shells

Be (Beryllium)

Atom

Mg (Magnesium) Atom

Elements in the same group have similar properties!

We can tell some properties of elements from their placement on the Periodic Table

The Noble Gasses are Un-reactive or Inert. They don’t form compounds easily with other elements. Their outer shells are full and have the

maximum amount of electrons they can hold. }8 outer

electrons

2 outer electrons

The Alkali Metals are very reactive and tend to lose one electron in order to have a full outer shell.

When they lose an electron they have a +1

charge.

The Alkaline Earth Metals are very reactive

and tend to lose two electrons in order to have a full outer shell. When they lose electrons they

have a +2 charge.

These elements are known as the Transition Metals

Most are good conductors of electricity.

The Halogens are poisonous and are fairly reactive.

Fluorine is the most reactive element. It can combine with

many other elements. Halogens tend to gain one electron and

then have a -1charge.

Solid Nonmetals are brittle and don’t conduct electricity. Some nonmetals are gasses or liquids.

NONMETALS GAIN OR ACCEPT ELECTRONS AND

WILL HAVE NEGATIVE CHARGES WHEN THEY DO.

Metalloids lie on either side of the stair-steps. They share properties with metals and

nonmetals. They are good semi-conductors

How can I remember the charge of an atom when it gains or loses electrons?

+1

+2 -2 -1

0

Nonmetals on the

right gain electrons

The left side of

the table is for

losers! Metals tend to

lose electrons

Bonding Atoms with charges (called Ions) can be

attracted to each other to form neutral compounds (all charges must add to zero) Ex: Na+1 and Cl-1 form NaCl Mg+2 will combine with two Cl-1 to form MgCl2

Ca+2 and O-2 will form MgO This type of bonding is called Ionic Bonding

NaCl: The electron Na+1 loses can be the same one Cl-1 gains.

The reaction of chlorine with sodium to form table salt. (Note: only valence electrons are shown in this simulation)

http://web.jjay.cuny.edu/~acarpi/NSC/5-bonds.htm

Groups of atoms with charges Sometimes groups

of atoms will act as a unit and carry a charge. NH4

+1

OH-1

CO3-2

SO4-2

PO4-3

These groups can also combine to form neutral compounds. Na+1 and OH-1

form NaOH NH4

+1 and CO3-2

form (NH4)2CO3

Al+3 and SO4-2

form Al2(SO4)3

How do I know how to do that? There is a quick way to determine the formula

of an ionic compound called the Crisscross Rule.

Example: What happens if you react aluminum and oxygen?

Al3+ O2-

Al2O3 How do you know the formula?

Charges are not considered as part of subscripts

Write the positive ion first, then the negative ion.

One more example

Compounds involving polyatomic ions work exactly the same way.

Example: A compound made from the ammonium cation and the sulfide anion:

NH4+1 S2-

(NH4)2S Remember that a 1 is understood, and not written.

Sharing Electrons Some times atoms share electrons to complete

their outer or valence energy level. This results in covalent bonding.

Oxygen has 6 valence electrons and

Hydrogen has 1. Each Hydrogen can share

its electron with oxygen giving each

atom a full outer shell.

Each Chlorine atom has 7 valence electrons. They can each share their unpaired electron so they have a full outer shell of 8.

Cl2

This atom has 4 protons (+)

so it is number 4 on the Periodic Table, Be

Elements with similar reactivity will be in the same group (column) on the Periodic Table,

and have the same number of valence or

outer electrons

Only Nonmetals Gain or Accept Electrons!

Fluorine is the only Nonmetal here!

CaCl2

Ca2+ Cl-

The Noble Gases have a full outer shell of electrons and don’t

react or form compounds easily.