Dmitri Mendeleev

A Russian chemist named Dmitri Mendeleev created the first widely accepted periodic table. He still relied on this idea of 8

groups, but he understood that many elements were still missing. He placed gaps in his periodic table where he thought these

elements belonged, and he correctly predicted these elements properties which validated his ordering of the elements.

Photo by Jurii

Elements are arranged and identified on the periodic table by the number of protons they

have in their nucleus.

The ATOMIC NUMBER is equal to the number of protons in an element. In its uncharged

atomic state, it is also equal to the number of electrons.

Elements also has an atomic mass listed. Remember atomic mass of an element is

different than the mass number of an isotope.

The ATOMIC MASS is equal to the number of grams in 1 mole of an element. Atomic mass is

sometimes referred to as atomic weight.

28.1 grams of siliconApproximately 1 mole of Si

It is very important that you can use the periodic table to distinguish metals from nonmetals.

Find the dark jagged line on the Periodic Table

On the left side of this line are all of the metals

On the right side of this line are

all of the nonmetals

Sodium

Beryllium

+ 2

+ 1

This gives metals a positive charge.

Positively charged ions are called cations.

When elements lose electrons and increase

their charge, we say that they have been oxidized.

This gives nonmetals a negative charge.

Negatively charged ions are called anions.

When elements gain electrons and lower

their charge, we say that they have been reduced.

Oxygen

Chlorine

- 2

- 1

Metals lose/donate electrons and nonmetals gain/accept electrons

This is whyMETALS react with

NONMETALS!

sodium chlorinesodium chloride

+1 -1

You need to understand the pattern of elements gaining and donating electrons on the periodic table.

Think about counting from the outside to the inside!

The metals in the middle of the periodic table are known as the transition metals.

Transition Metals

The elements that lay on either side of the dark, jagged have rather unique properties. Sometimes they behave like metals, and sometimes they behave like nonmetals.

Because of this, they are called Metalloids

You also need to know that Iron, Cobalt, and Nickel have special properties such as the ability to be made into magnets. Together, these three elements are known as the .Iron Triad

Iron Triad

s p

The elements whose valence electrons are in the s and p sublevels are known as the representative

elements. The number of valence electrons of these elements is followed by an A.

d

f

The elements whose valence electrons are in the d and f sublevels are known as the transition

elements. The number of valence electrons of these elements is followed by a B.

There are several groups/families on the periodic table whose name you should have memorized.

Group 1 = Alkali MetalsGroup 2 = Alkaline Earth MetalsGroup 17 = HalogensGroup 18 = Noble Gases

Elements in the same group/family have similar

physical and chemical properties because they all have the same number of

valence electrons!

All of the elements in group 16 have 6 valence electrons

Columns on the periodic table are known as groups

or families.

How many valence electrons do the elements of group 2 have?

2A = 2

How many valence electrons do the elements of group 6 have?

6B = 6

How many valence electrons do the elements of group 17 have?

7A = 7

How many valence electrons does sulfur have?

6A = 6

Which group on the periodic table undergoes the fewest chemical reactions?

They are inert gases. This is because they have 8 valence electrons and their s and p sublevels are full.

Inert means they resist chemical reactions!

The Periodic Table can be used to determine the charge of the representative elements when they become ions!

+1

+2 +3+4or-4 -3 -2 -1

0

Determine the charge of each of the elements on your notes.

+1 -1 +2-2 -3 -1-2 +1 +2+2 -1 0

Noble Gases do not become ions. This is why we say they have a charge of zero (0)

The transition metals are the d-block elements. Because of this, the number of electrons they will lose is less predictable.

You will know the charge of a transition metal by the ROMAN NUMERAL in its name!

Iron (III) has a ____ charge.Iron (II) has a ____ charge.

copper (I) has a ____ charge.copper (II) has a ____ charge.

+3+2

+1+2

Determine the charge of each of the transition metals on your notes.

+2 +4 +3+4 +2 +3

Why is the charge of a transition metal always positive?

Metals ______________ electrons.This gives them a ____ charge.

Positively charged ions are called ________.

lose/donate+

Remember:

Since all of the transition elements are metals, they will all be cations!

Metals

cations

Ionic compounds are ALWAYS between a metal and a nonmetal.

On the left side of this line are all of the metals

On the right side of this line are

all of the nonmetals

Covalent compounds are ALWAYS between nonmetals.

On the right side of this line are

all of the nonmetals

The formula above shows the ratio of an unidentified element, X, to sodium in an ionic salt. In which group on the periodic table does Element X most likely belong?

A Group 1 B Group 2 C Group 17 D Group 18

Since it is an ionic salt, it has to be a nonmetal since sodium is a metal. It cannot be group 18 since group 18 is the inert noble gases that would not react with sodium.

Understanding the previous facts at a conceptual level is critical to your success in chemistry. Using this knowledge, determine the identity of each of the following unknown elements.

The formula above shows the ratio of an unidentified element, X, to fluorine in an ionic salt. Which group below is most likely the identity of Element X?

A sulfur B lithium C arsenic D krypton

Since it is an ionic salt, it has to be a metal since fluorine is a nonmetal. Ionic compounds have both a metal and a nonmetal.

The formula above shows the ratio of an unidentified element, X, to chlorine in a covalent molecule. Which element below is most likely the identity of Element X?

A sodium B neon C phosphorous D copper

Since it is a covalent molecule, it has to be a nonmetal. It cannot be neon since neon is an inert noble gas that would not react with chlorine.