Today’s Agenda .t 10/5/10Recall

Periodic Table Connection

Periodic Table Webclips

Homework

Recall• Write the following questions in your notebook and

answer them to the best of your ability.

• No attempt = No stampNo Recall = No stamp (for tomorrow's stamp)

• Write the Electron configuration for atomic numbers 8, 16, 34. Include the names of the elements.

• What is a numeric similarity of these 3 elements? (look at the last orbitals)

The Periodic Table connection

By now you should have noticed that elements in the same group or family share the same number of valence electrons.

Elements in the same group react similarly Period numbers can be seen as energy levels.

Go to page 119 and look at figure 3.

Don't write down

Periodic Law

When the elements are arranged according to their atomic numbers, elements with similar properties appear at regular intervals.

Some videos

Write down key points from these videos:

http://my.hrw.com/sh2/sh07_10/student/tabpages/hw7c/c04/s01/vc02/hw7c_c04s01_vc02fs.htm

http://my.hrw.com/sh2/sh07_10/student/tabpages/hw7c/c04/s03/vc02/hw7c_c04s03_vc02fs.htm

• Dmitri Medeleev gave us a functional scheme with which to classify elements.– Mendeleev’s scheme was based on chemical properties of

the elements.– It was noticed that the chemical properties of elements

increased in a periodic manner.– The periodicity of the elements was demonstrated by

Medeleev when he used the table to predict to occurrence and chemical properties of elements which had not yet been discovered.

• Mendeleev left blank spaces in his table when the properties of the elements above and below did not seem to match. The existence of unknown elements was predicted by Mendeleev on the basis of the blank spaces. When the unknown elements were discovered, it was found that Mendeleev had closely predicted the properties of the elements as well as their discovery.

• The Periodic Law– Similar physical and chemical properties recur

periodically when the elements are listed in order of increasing atomic number.

• The Modern Periodic Table

• Introduction– The periodic table is made up of rows of elements and

columns.– An element is identified by its chemical symbol.– The number above the symbol is the atomic number– The number below the symbol is the rounded atomic

weight of the element.– A row is called a period– A column is called a group

• (A) Periods of the periodic table, and (B) groups of

the periodic table.

• Periodic Patterns– The chemical behavior of elements is determined by its

electron configuration– Energy levels are quantized so roughly correspond to

layers of electrons around the nucleus.– A shell is all the electrons with the same value of n.

• n is a row in the periodic table.

– Each period begins with a new outer electron shell

– Each period ends with a completely filled outer shell that has the maximum number of electrons for that shell.

– The number identifying the A families identifies the number of electrons in the outer shell, except helium

– The outer shell electrons are responsible for chemical reactions.

– Group A elements are called representative elements– Group B elements are called transition elements.

• Chemical “Families”– IA are called alkali metals because the react with water

to from an alkaline solution– Group IIA are called the alkali earth metals because

they are reactive, but not as reactive as Group IA.• They are also soft metals like Earth.

– Group VIIA are the halogens• These need only one electron to fill their outer shell

• They are very reactive.

– Group VIIIA are the noble gases as they have completely filled outer shells

• They are almost non reactive.

• Four chemical families of the periodic table: the alkali metals (IA), the alkaline earth metals (IIA), halogens (VII), and the noble gases (VIIIA).

Metal: Elements that are usually solids at room temperature. Most elements are metals.

Non-Metal: Elements in the upper right corner of the periodic Table. Their chemical and physical properties are differentfrom metals.

Metalloid: Elements that lie on a diagonal line between the Metals and non-metals. Their chemical and physical properties are intermediate between the two.

– When an atom or molecule gain or loses an electron it becomes an ion.• A cation has lost an electron and therefore has a

positive charge• An anion has gained an electron and therefore has a

negative charge.

– Elements with 1, 2, or 3 electrons in their outer shell tend to lose electrons to fill their outer shell and become cations.

• These are the metals which always tend to lose electrons.

– Elements with 5 to 7 electrons in their outer shell tend to gain electrons to fill their outer shell and become anions.

• These are the nonmetals which always tend to gain electrons.

– Semiconductors (metalloids) occur at the dividing line between metals and nonmetals.

What would the charge be on a sodium ion?

EXAMPLE

Since sodium in in Group IA it is a metal and so wouldLOSE an electron

You can tell how many would be lost by the group numberGroup 1A elements lose 1 electron

So the charge would be +1Remember an electron is negatively charged. When you lose them atom becomes positively charged…

when you gain them it becomes negatively charged

Homework

• Read Chapter 4 section 1And answer Questions #2, 5, 6, 7, 8 & 13• No work = No red stamp tomorrow• Remember, your atomic packet it due this

Friday