Periodic Table of Elements

Mendeleev

In 1869, Dmitri Ivanovitch Mendeléev created the first accepted version of the periodic table.

He grouped elements according to their atomic mass, and as he did, he found that the families had similar chemical properties. 

Blank spaces were left open to add the new elements he predicted would occur. 

The Current Periodic Table

Mendeleev wasn’t too far off. Now the elements are put in rows by

increasing ATOMIC NUMBER!! The horizontal rows are called periods and

are labeled from 1 to 7. The vertical columns are called groups or

families and are labeled from 1 to 18.

Elements

Science has come along way since Aristotle’s theory of Air, Water, Fire, and Earth.

Scientists have identified 90 naturally occurring elements, and created about 28 others.

Elements The elements, alone or in

combinations, make up our bodies, our world, our sun, and in fact, the entire universe.

Almost all elements are made up of 3 sub atomic particles. Protons (+), neutrons (0) & electrons (-)

The most abundant element in the earth’s crust is oxygen.

Periodic Table The periodic table organizes the elements in a

particular way. A great deal of information about an element can be gathered from its position in the period table.

For example, you can predict with reasonably good accuracy the physical and chemical properties of the element. You can also predict what other elements a particular element will react with chemically.

Understanding the organization and plan of the periodic table will help you obtain basic information about each of the 118 known elements.

What’s in a square?

Different periodic tables can include various bits of information, but usually: atomic number symbol atomic mass

Key to the Periodic Table Elements are organized on

the table according to their atomic number, usually found near the top of the square. The atomic number refers

to how many protons or electrons an atom of that element has.

For instance, hydrogen has 1 proton, so it’s atomic number is 1.

The atomic number is unique to that element. No two elements have the same atomic number.

Symbols All elements have their

own unique symbol. It can consist of a single

capital letter, or a capital letter and one or two lower case letters.

Elements have their name for a variety of reasons. Some are named after mythology, countries, scientists or in Latin or Greek.

C Carbon

CuCopper

Atomic Number

This refers to how many protons or electrons an atom of that element has.

No two elements, have the same number of protons.

Bohr Model of Hydrogen Atom

Atomic Mass

Atomic Mass refers to the “weight” of the atom.

It is derived at by adding the number of protons with the number of neutrons.

This is a helium atom. Its atomic mass is 4 (protons plus neutrons).

What is its atomic number?

Atomic Mass Unit (AMU)

The unit of measurement for an atom is an AMU. It stands for atomic mass unit.

One AMU is equal to the mass of one proton.

Atomic Mass Unit (AMU)

There are

6 X 1023 or 600,000,000,000,000,000,000,000 amus in one gram.

(Remember that electrons are 2000 times smaller than one amu).

Atomic Mass and Isotopes While most atoms have the same number of protons and

neutrons, some don’t. Some atoms have more or less neutrons than protons.

These are called isotopes. An atomic mass number with a decimal is the total of the

number of protons plus the average number of neutrons. We write isotopes like this: Uranium has 2 isotopes: Uranium – 238 & Uranium - 239

U238

92

Mass #

Atomic # U239

92

Isotope ExamplesList the protons, neutrons, electrons and the symbol Carbon – 12 Carbon – 13 Carbon – 14 Note:

The # of neutrons may vary. Isotopes have different mass numbers. Isotopes of the same element are still chemically alike

because they have the same number of protons and electrons.

Properties of Metals Metals are good conductors

of heat and electricity. Metals are shiny. Metals are ductile (can be

stretched into thin wires). Metals are malleable (can be

pounded into thin sheets). A chemical property of metal

is its reaction with water which results in corrosion.

Properties of Non-Metals

Non-metals are poor conductors of heat and electricity.

Non-metals are not ductile or malleable.

Solid non-metals are brittle and break easily.

They are dull (not shiny).

Many non-metals are gases.

Sulfur

Properties of Metalloids

Metalloids (metal-like) have properties of both metals and non-metals.

They are solids that can be shiny or dull.

They conduct heat and electricity better than non-metals but not as well as metals.

They are brittle and not ductile

Silicon

A Family is also called a Group.

based on their atomic numbers.

Groups or Groups or FamiliesFamilies

Columns of elements are Columns of elements are called groups or families. called groups or families.

Elements in each family Elements in each family have similar but not have similar but not identical properties.identical properties.

For example, lithium (Li), For example, lithium (Li), sodium (Na), potassium (K), sodium (Na), potassium (K), and other members of family and other members of family IA are all soft, white, shiny IA are all soft, white, shiny metals.metals.

All elements in a family have All elements in a family have the same number of valence the same number of valence electrons.electrons.

Each horizontal row of Each horizontal row of elements is called a period.elements is called a period.

The elements in a period are The elements in a period are not alike in properties.not alike in properties.

In fact, the properties change In fact, the properties change greatly across even given greatly across even given row.row.

The first element in a period The first element in a period is always an extremely active is always an extremely active solid. The last element in a solid. The last element in a period, is always an inactive period, is always an inactive gas.gas.

The period tells us how many The period tells us how many orbitals the element has.orbitals the element has.

Periods

Valence Electrons

The number of valence electrons an atom has may also appear in a square.

Valence electrons are the electrons in the outer energy level of an atom.

These are the electrons that are transferred or shared when atoms bond together.

What does it mean to be reactive?

We will be describing elements according to their reactivity.

Elements that are reactive bond easily with other elements to make compounds.

Some elements are only found in nature bonded with other elements.

What makes an element reactive? An incomplete valence electron level. All atoms (except hydrogen) want to have 8 electrons

in their very outermost energy level (This is called the octet rule.)

Atoms bond until this level is complete. Atoms with less than 4 valence electrons lose them during bonding. Atoms with 6, 7, or 8 valence electrons gain electrons during bonding.

Elements that have either gained or lost electrons are called ions.

Positively charged: Cations Any atom that loses electrons to form

compounds are called cations. Cations have a positive charge.

Naming cations: Use the element name followed by the word “ion”. Some Cations have more than one charged form.

Cation formula systematic name common name

Fe2+ iron(II) ion ferrous ion  

Fe3+ iron(III) ion ferric ion  

Cu1+ copper(I) ion cuprous ion  

Cu2+ copper(II) ion cupric ion  

Hg1+ mercury(I) ion mercurous ion

 

Hg2+ mercury(II) ion mercuric ion  

Pb2+ lead(II) ion plumbous ion

 

Pb4+ lead(IV) ion plumbic ion  

Sn2+ tin(II) ion stannous ion  

Sn4+ tin(IV) ion stannic ion  

 

Table: Metal cations with more than one common charged form

Elements that have either gained or lost electrons are called ions.

Negatively charged: Anions Atoms that gain electrons to form

compounds are called anions. Anions have a negative charge.

Naming Anions: Drop the last few letters of the element name and add “ide”.

5

How can we determine the charge of an ion?

For some of the elements it is very easy. Elements in groups 1, 2, 13, 14, 15, 16, & 17 will lose or gain electrons so they have the same # as the nearest Noble Gas (group 18).

The transition metals (groups 3- 12) cannot have their charges predicted in this way due to many of them having isotopes. Their charges must be predicted in other ways.

Noble Gases

Noble Gases are colorless gases that are extremely un-reactive. One important property of the noble gases is their inactivity. They are

inactive because their outermost energy level is full. Because they do not readily combine with other elements to form

compounds, the noble gases are called inert. The family of noble gases includes helium, neon, argon, krypton,

xenon, and radon. All the noble gases are found in small amounts in the earth's

atmosphere.

Bohr’s Model of the Atom

Electrons orbit the nucleus at a fixed distance.

Each orbit is associated with a definite energy level.

Bohr Model

Energy levels are quantized

Electrons travel in orbits around the nucleus

The farther the electron is from the nucleus the more energy it has.

• If you want to see how atoms of one element will react, it is handy to have an easier way to represent the atoms and the electrons in their outer energy levels.

Electron Dot Diagrams

• You can do this with electron dot diagrams.

• An electron dot diagram is the symbol for the element surrounded by as many dots as there are electrons in its outer energy level.

• The dots are written in pairs on four sides of the element symbol.

How to Write Them

• Start by writing one dot on the top of the element symbol, then work your way around adding dots to the right, bottom, and left.

How to Write Them

• Add a fifth dot to the top to make a pair. Continue in this manner until you reach the number of valence electrons the element has or until there are eight dots to complete the level.

Forming Compounds

Sodium is an element. Chlorine is an

element. When sodium and

chlorine bond they make the compound sodium chloride, commonly known as table salt.

Compounds have different properties than the elements that make them up.

Table salt has different properties than sodium, an explosive metal, and chlorine, a poisonous gas.

Forming Compounds

A chemical bond is formed when valence electrons of atoms interact and become stable.

Ionic Compounds – substances composed of cations and anions forming ionic bonds. Certain combinations of elements form ionic

bonds groups 1, 2, and 3 metals with group 16 & 17 nonmetals.

Eg. Na+ + Cl- NaCl

Forming Compounds

Covalent bond – A bond formed when atoms share 2 or more pairs of electrons.

A neutral particle that is composed of atoms joined together by covalent bonds is called a molecule.

Eg. Diatomic molecules

Molecules that contain two (“di”) atoms. “The Magic 7” + Hydrogen – These

elements are never found by themselves in nature, they are always in pairs. Mark them on your periodic table. H, N, O, F, Cl, Br, I, At These start at the element #7 They form the shape of a 7

Naming Formulas

Binary Compounds – Contain 2 different elements. The name usually ends in “ide” Eg. sodium chloride.

When combining 2 ions, you need to create a net charge of zero.

Eg. Ca2+ + Cl- CaCl2 (2 positives, 2 negatives = 0 charge)

Crossing Over Method

Ca2+ + O2-

(2’s cancel out) CaO = Calcium Oxide

Mg2+ + Cl- = Magnesium Chloride

Ca2O2

MgCl2

Do Investigations Exercise on pg. 156-158 in text

Polyatomic Ions

Consists of 2 or more different non metals like ammonium (NH4 = Nitrogen and 4 Hydrogen). See list on page 159.

Eg. NH4+ + OH- NH4OH = Ammonium hydroxide

Parentheses may be needed for polyatomic ions.

Fe3+ + OH- Fe(OH)3 = Iron (III) hydroxide

Things to look for If cations have (), the number inside the () is

their charge. Not how many. If anions end in -ide they are probably off the

periodic table (Monoatomic) If anion ends in -ate or -ite it is polyatomic. The positive piece always gets written first. Hydrogen- it depends on where it’s at

If it is first, it is a metal – hydrogen ion If it is second, it’s a nonmetal - hydride