Elements

Learning about the Elements

and the Periodic Table

What is the Periodic Table?

A chemical element or element is a chemical substance consisting of atoms having the same number of protonsin their atomic nuclei (i.e. the same atomic number, Z). There are 118 elements that have been identified, of which the first 94 occur naturally on Earth with the remaining 24 being synthetic elements. There are 80 elements that have at least one stable isotope and 38 that have exclusively radioactive isotopes, which decay over time into other elements. Iron is the most abundant element (by mass) making up the Earth, while oxygen is the most common element in the crust of the earth.

Chemical elements constitute approximately 15% of the matter in the universe: the remainder is dark matter, the composition of it is unknown, but it is not composed of chemical elements. The two lightest elements, hydrogen and helium were mostly formed in the beginning of the Universe and are the most common elements.

When different elements are chemically combined, with the atoms held together by chemical bonds, they formchemical compounds. Only a minority of elements are found uncombined as relatively pure minerals. Among the more common of such "native elements" are copper, silver, gold, carbon (as coal, graphite, or diamonds), andsulfur. All but a few of the most inert elements, such as noble gases and noble metals, are usually found on Earth in chemically combined form, as chemical compounds. While about 32 of the chemical elements occur on Earth in native uncombined forms, most of these occur as mixtures. For example, atmospheric air is primarily a mixture ofnitrogen, oxygen, and argon, and native solid elements occur in alloys, such as that of iron and nickel.

The history of the discovery and use of the elements began with primitive human societies that found native elements like carbon, sulfur, copper and gold. Later civilizations extracted elemental copper, tin, lead and iron from their ores by smelting, using charcoal. Alchemists and chemists subsequently identified many more, with almost all of the naturally-occurring elements becoming known by 1900.

The properties of the chemical elements are summarized on the periodic table, which organizes the elements by increasing atomic number into rows ("periods") in which the columns ("groups") share recurring ("periodic") physical and chemical properties. Save for unstable radioactive elements with short half-lives, all of the elements are available industrially, most of them in high degrees of purity.

When an atom has some protons and neutrons in the nucleus and some electrons zipping around in orbitals that begin to combine in specific numbers they begin to form recognizable traits we call compounds. If you have eight protons, neutrons and electrons, you will have an oxygen(O) atom. If you have seven protons, neutrons, and electrons, you will have a nitrogen (N) atom. The atoms for each element are unique, even though they are all made of similar subatomic parts.

you are made up of billions of billions of atoms but you probably won't find more than 40 elements (types of atoms) in your body. Chemists have learned that over 95% of your body is made up of hydrogen (H), carbon (C), nitrogen, oxygen, phosphorus (P), and calcium (Ca).

What is the Periodic Table?

There are a limited number of basic elements. Up to this point in time, we have discovered or created about 120. Scientists just confirmed the creation of element 117 in 2014. While there are more elements to discover, the basic elements remain the same. Iron (Fe) atoms found on Earth are identical to iron atoms found on meteorites. The iron atoms in the red soil of Mars are also the same.

The List of Elements

Since the launch of the site, we've been asked, "Why start with 18?" The rules for the first eighteen elements are very straightforward:

(1) Electrons fit nicely into three orbitals. Remember that the orbitals are the places you will generally find the electrons as they spin around the nucleus.
(2) These eighteen elements make up most of the matter in the Universe.
(3) It's a lot easier to remember facts about 18 elements than over 100 elements.

Element 1: Hydrogen
Element 2: Helium
Element 3: Lithium
Element 4: Beryllium
Element 5: Boron
Element 6: Carbon
Element 7: Nitrogen
Element 8: Oxygen
Element 9: Fluorine
Element 10: Neon
Element 11: Sodium
Element 12: Magnesium
Element 13: Aluminum
Element 14: Silicon
Element 15: Phosphorus
Element 16: Sulfur
Element 17: Chlorine
Element 18: Argon

As we move past the first eighteen elements, you can start to learn about transition elements in the fourth period (row) of the periodic table. The transition metals have electron configurations that are a little different from the first eighteen. Make sure you understand the basics of electron orbitals before you move on to this row.

Element 19: Potassium
Element 20: Calcium
Element 21: Scandium
Element 22: Titanium
Element 23: Vanadium
Element 24: Chromium
Element 25: Manganese
Element 26: Iron
Element 27: Cobalt
Element 28: Nickel
Element 29: Copper
Element 30: Zinc
Element 31: Gallium
Element 32: Germanium
Element 33: Arsenic
Element 34: Selenium
Element 35: Bromine
Element 36: Krypton

Elements as Building Blocks

The periodic table is organized like a big grid. Each element is placed in a specific location because of its atomic structure. As with any grid, the periodic table has rows (left to right) and columns (up and down). Each row and column has specific characteristics. For example, beryllium (Be) andmagnesium (Mg) are found in column two and share certain similarities while potassium (K) and calcium (Ca) from row four share different characteristics.

You've got Your Periods...

Even though they skip some squares in between, all of the rows read left to right. When you look at the periodic table, each row is called a period (Get it? Like PERIODic table.). All of the elements in a period have the same number of atomic orbitals. For example, every element in the top row (the first period) has one orbital for its electrons. All of the elements in the second row (the second period) have two orbitals for their electrons. As you move down the table, every row adds an orbital. At this time, there is a maximum of seven electron orbitals.

...and Your Groups

Now you know about periods going left to right. The periodic table also has a special name for its vertical columns. Each column is called a group. The elements in each group have the same number of electrons in the outer orbital. Those outer electrons are also called valence electrons. They are the electrons involved in chemical bonds with other elements.

Every element in the first column (group one) has one electron in its outer shell. Every element in the second column (group two) has two electrons in the outer shell. As you keep counting the columns, you'll know how many electrons are in the outer shell. There are exceptions to the order when you look at the transition elements, but you get the general idea. Transition elements add electrons to the second-to-last orbital.

For example, nitrogen (N) has the atomic number seven. The atomic number tells you there are seven electrons in a neutral atom of nitrogen. How many electrons are in its outer orbital? Nitrogen is in the fifteenth column, labelled 'Group VA'. The 'V' is the Roman numeral for five and represents the number of electrons in the outer orbital. All of that information tells you there are two electrons in the first orbital and five in the second (2-5).

Phosphorus (P) is also in Group VA which means it also has five electrons in its outer orbital. However, because the atomic number for phosphorus is fifteen, the electron configuration is 2-8-5.

Two at the Top

Hydrogen (H) and helium (He) are special elements. Hydrogen can have the electron traits of two groups: one and seven. For chemists, hydrogen is sometimes missing an electron like the members of group IA, and sometimes has an extra one as in group VIIA. When you study acids and bases you will regularly work with hydrogen cations (H+). A hydride is a hydrogen anion and has an extra electron (H-).

Helium (He) is different from all of the other elements. It is very stable with only two electrons in its outer orbital (valence shell). Even though it only has two, it is still grouped with the noble gases that have eight electrons in their outermost orbitals. The noble gases and helium are all "happy," because their valence shell is full.

Why are the First 18 Elements Special?

(1) The electrons fit nicely into three orbitals. Remember that the electrons spin around the nucleus in regions called orbitals.
(2) These elements make up most of the matter in the Universe.
(3) It is a lot easier to remember facts about 18 elements as opposed to over 100 elements

THe Next 18 Elements

If you want to keep going, we have added elements 18-36. You can learn about element origins, pronunciation, atomic structure, and periodic table locations. This next set of elements is from the fourth period/row of the table. Be aware... There are additional rules about electron orbitals because of the transition metals. We tried to make things as simple as possible.

Families Stick Together

We just covered the columns and rows of the periodic table. There are also other, less specific, groups of elements. These groups are all over the table. Scientists group these families of elements by their chemical properties. Each family reacts in a different way with the outside world. Metals behave differently than gases, and there are even different types of metals. Some elements don't react, while others are very reactive, and some are good conductors of electricity.

The columns of the periodic table are often used to define families. Thenoble gases are all located in the far right column of the table. That column is labeled Group Zero. Other families can be made of elements in a series. A good example of a series of elements is the transition metal family.

The thing to remember is that a family of elements can be found in several ways. You need to run tests and study the elements to determine their properties. Only after that testing can you determine what family an element belongs in.

Examples of Families

- Alkali Metals
- Alkaline Earth Metals
- Transition Metals
- Halogen Gases
- Noble Gases

Examples of Physical Properties

- Density
- Boiling Point
- Melting Point
- Conductivity
- Heat Capacity

Examples of Chemical Properties

- Valence
- Reactivity
- Radioactivity

Halogens on the Right

In the second column from the right side of the periodic table, you will find Group Seventeen (Group XVII). This column is the home of the halogen family of elements. Who is in this family? The elements included are fluorine (F), chlorine (Cl), bromine (Br), iodine (I), and astatine (At).

What Makes Them Similar?

When you look at our descriptions of the elements fluorine and chlorine, you will see that they both have seven electrons in their outer shell. That seven-electron trait applies to all of the halogens. They are all just one electron shy of having full shells. Because they are so close to being happy, they have the trait of combining with many different elements. They are very reactive. You will often find them bonding with metals and elements from Group One of the periodic table. The elements in the column on the left each have one electron that they like to donate.

We've just told you how reactive the halogens are. Not all halogens react with the same intensity or enthusiasm. Fluorine is the most reactive and combines with most elements from around the periodic table. Reactivity decreases as you move down the column. As you learn more about the table, you will find this pattern true for other families. As the atomic number increases, the atoms get bigger. Their chemical properties change just a little bit when compared to the element right above them on the table.

What is a Halide?

The elements we are talking about in this section are called halogens. When a halogen combines with another element, the resulting compound is called a halide. One of the best examples of a halide is sodium chloride (NaCl). Don't think that the halogens always make ionic compounds and salts. Some halides of the world are a part of molecules with covalent bonds.

The Noble Gases

We love the noble gases. Some scientists used to call them the inert gases. It didn't really work because there are a few other gases that are basically inert but not noble gases. Nitrogen (N2) might be considered an inert gas, but it is not a noble gas. The noble gases are another family of elements, and all of them are located in the far right column of the periodic table. For all of you budding chemists, the far right is also known as Group Zero (Group 0) or Group Eighteen (Group XVIII). This family has the happiest elements of all.

Why Are They Happy?

Using the Bohr description of electron shells, happy atoms have full shells. All of the noble gases have full outer shells with eight electrons. Oh, wait! That's not totally correct. At the top of the noble gases is little helium (He), with a shell that is full with only two electrons. The fact that their outer shells are full means they are quite happy and don't need to react with other elements. In fact, they rarely combine with other elements. That non-reactivity is why they are called inert.

Who's in the Family?

All of the elements in Group Zero are noble gases. The list includes helium, neon (Ne), argon (Ar), krypton (Kr), xenon (Xe), and radon (Rn). Don't think that, because these elements don't like to react, we don't use them. You will find noble gases all over our world. Neon is used in advertising signs. Argon is used in light bulbs. Helium is used in balloons and to cool things. Xenon is used in headlights for new cars. Because of their chemical properties, these gases are also used in the laboratory to help stabilize reactions that would usually proceed too quickly. When you move down the periodic table, as the atomic numbers increase, the elements become rarer. They are not just rare in nature, but rare as useful elements, too.

But Wait, They Do Bond!

Some do. As of about 40 years ago, scientists have been able to make some compounds with noble gases. Some have been used in compounds to make explosives, and others just form compounds in a lab. The thing to remember is that they were forced. When going about their natural lives, you will never (well, never say never, because there may be an exception) find the noble gases bonded to other elements.

Metal Basics

We wanted to give you a big overview ofmetals before we get into details about specific families. Almost 75% of all elements are classified as metals. They are not all like silver (Ag), gold (Au), or platinum (Pt). Those are the very cool and shiny ones. There are other metals like potassium (K) and iridium (Ir) that you might not think about right away.

Many Kinds of Metals

How many kinds of metals are there? So many. Don't even try to memorize them all. Just remember the ones you might need in class. Here's a quick list: Actinide Metals, Lanthanide Metals, Alkali Metals, Alkaline-Earth Metals, Rare Metals, Rare-Earth Metals, and Transition Metals. Remember, that's the easy list. Lucky for you, the periodic table is excellent at organizingelements, and you will find each of these groups in specific areas of the periodic table.

How Do You Identify a Metal?

What are the characteristics of metals? We've got four traits that will help you identify whether an element is a metal or not:

1. Conduction: Metals are good at conducting electricity. Silver (Ag) and copper (Cu) are some of the most efficient metals and are often used in electronics.

2. Reactivity: Metals are very reactive, some more than others, but most form compounds with other elements quite easily. Sodium (Na) and potassium (K) are some of the most reactive metals. A metal like iron (Fe) forms iron oxide (Fe2O3), which you know as rust.

3. Chemical: It gets a little complex here. Metals usually make positive ions when the compounds are dissolved in solution. Also, their metallic oxides make hydroxides (bases) (OH-), and not acids, when in solution. Think about this example: When sodium chloride (NaCl) is dissolved in water (H2O), it breaks apart into sodium (Na+) and chlorine (Cl-) ions. Do you see how that sodium is the positive ion? Sodium is the metal. It works that way for other metals. Potassium chlorine (KCl) works the same way. When it is dissolved, the potassium ion (K+) is the positive ion.

4. Alloys: Metals are easily combined. Mixtures of many metallic elements are called alloys. Examples of alloys are steel and bronze.

Alkali Metals to the Left

Let's go to the left side of the periodic table. When looking for families, the first one you will find is the alkali metal family of elements. They are also known as thealkaline metals. You should remember that there is a separate group called the alkaline earth metals in Group Two. They are a very different family, even though they have a similar name. That far left column is Group One (Group I). When we talk about the groups of the periodic table, scientists use Roman numerals when they write them out. The "one" in this case refers to having one electron in the outermost orbital.

A Family Portrait

Who's in the family? Starting at the top we find hydrogen (H). But wait. That element is NOT in the family. When we told you about families, we said that they were groups of elements that react in similar ways. Hydrogen is a very special element of the periodic table and doesn't belong to any family. While hydrogen sits in Group I, it is NOT an alkali metal.

Family Bonding

Now that we've covered that exception, the members of the family include: lithium (Li), sodium (Na), potassium (K), rubidium (Rb), cesium (Cs) and francium (Fr). As with all families, these elements share traits. They are very reactive. Why? They all have one electrons in their outer shell. That's one electron away from being happy (full shells). When you are that close to having a full shell, you want to bond with other elements and lose that electron. An increased desire to bond means you are more reactive. In fact, when you put some of these pure elements in water (H2O), they can cause huge explosions.

The alkali metals are also metals. That seems obvious from the name. Often, in chemistry, characteristics are assigned by the way elements look. You will find that the alkali group is shiny and light in weight. Their light weight and physical properties separate them from other metals. They aremalleable (bendable) and sometimes soft enough to be cut with a dull knife. Alkali metals are not the type of metals you would use for coins or houses.

Heading to Group Two

So we just covered the alkali metals in Group I. You will find the alkaline earth metals right next door in Group II. This is the second most reactive family of elements in the periodic table. Do you know why they are called alkaline? When these compounds are mixed in solutions, they are likely to form solutions with a pH greater than 7. Those higher pH levels means that they are defined as "basic" or "alkaline" solutions.

A Family Portrait

Who's in the family? The members of the alkaline earth metals include: beryllium (Be), magnesium (Mg), calcium (Ca), strontium (Sr), barium (Ba) and radium (Ra). As with all families, these elements share traits. While not as reactive as the alkali metals, this family knows how to make bonds very easily. Each of them has two electrons in their outer shell. They are ready to give up those two electrons in electrovalent/ionic bonds. Sometimes you will see them with two halogen atoms, as with beryllium fluoride (BeF2), and sometimes they might form a double bond, as with calcium oxide (CaO). It's all about giving up those electrons to have a full outer shell.

As you get to the bottom of the list, you will find the radioactive radium. While radium is not found around your house anymore, it used to be an ingredient in glow-in-the-dark paints. It was originally mixed with zinc sulfide (ZnS). The other elements are found in many items, including fireworks, batteries, flashbulbs, and special alloys. The lighter alkaline earth metals, such as magnesium and calcium, are very important in animal and plant physiology. You all know that calcium helps build your bones. Magnesium can be found in chlorophyll molecules.

Transitioning

Let's start off by telling you that there are a lot of elements that are consideredtransition metals. Which metals are the transition metals?
21 (Scandium) through 29 (Copper)
39 (Yttrium) through 47 (Silver)
57 (Lanthanum) through 79 (Gold)
89 (Actinium) and all higher numbers.

What Makes Them So Special?

It all has to do with their shells/orbitals. We like introducing students to the first eighteen elements, because they are easier to explain. Transition metals are good examples of advanced shell and orbital ideas. They have a lot of electrons and distribute them in different ways. You will usually find that transition metals are shiny, too. Not all of them, but we are sure you've seen pictures of silver (Ag), gold (Au), and platinum (Pt).

Transition metals are able to put more than eight electrons in the shell that is one in from the outermost shell. Think about argon (Ar). It has 18 electrons set up in a 2-8-8 order. Scandium (Sc) is only 3 spots away with 21 electrons, but it has a configuration of 2-8-9-2. Wow! This is where it starts. This is the point in the periodic table where you can place more than 8 electrons in a shell. You need to remember that those electrons are added to the second-to-last shells.

The transition metals are able to put up to 32 electrons in their second-to-last shell. Something like gold (Au), with an atomic number of 79, has an organization of 2-8-18-32-18-1. Of course, there are still some rules. No shell can have more than 32 electrons. You will find it's usually 2, 8, 18 or 32 for the maximum number of electrons in an orbital.

One More Thing

Most elements can only use electrons from their outer orbital to bond with other elements. Transition metals can use the two outermost shells/orbitals to bondwith other elements. It's a chemical trait that allows them to bond with many elements in a variety of shapes. Why can they do that? As you learn more, you will discover that most transition elements actually have two shells that are not happy. Whenever you have a shell that is not happy, the electrons want to bond with other elements. Example: Molybdenum (Mo), with 42 electrons. The configuration is 2-8-18-13-1. The shells with 13 and 1 are not happy. Those two orbitals can use the electrons to bond with other atoms.

Lanthanide Series of Metals

When you look at the periodic table, you will see two rows that kind of sit off to the bottom. They are part of the whole table, but it is easier to print the table when they are on the bottom. One of those rows is called the lanthanide series. There are a bunch of names you may hear that describe these 15 elements. Some people say lanthanide, some say rare-earthmetals, and some say inner-transition elements. No matter what you choose, everyone will know what you mean if you say lanthanide.

Meet the Family

The lanthanide family is comprised of fifteen elements starting with lanthanum (La) at atomic number 57 and finishing up with lutetium (Lu) at number 71 It's doubtful your teachers will ever ask you to remember all of the elements in the series. Just remember lanthanum. You might find some of these elements in superconductors, glass production, or lasers.

Actinide Series of Metals

There are two rows under the periodic table: the lanthanide and actinide series. The lanthanide series can be found naturally on Earth. Only one element in the series is radioactive. The actinideseries is much different. They are allradioactive and some are not found in nature. Some of the elements with higher atomic numbers have only been made in labs. There are special laboratories across the world that specialize in experimenting on elements. Some of these particle accelerators have pounded atomic particles into elements with lower atomic numbers. The buildup of additional parts creates short-lived, high atomic number elements.

Meet the Family

The actinide family is comprised of fifteen elements that start with actinium (Ac) at atomic number 89 and finish up with lawrencium (Lr) at number 103. It's doubtful your teachers will ever ask you to remember all of the elements in the series. You have probably heard of plutonium (Pu), since it was used in atomic bombs. Uranium (U) is also well known for itsradioactivity. They aren't all used to blow up the world. Some of them help us out every day. You can find americium (Am) is some metal detectors.