Sometimes hydrogen H is placed in Group 17, above fluorine F , because it has similar properties to the nonmetals in that group; for example, in its elemental state hydrogen exists as a diatomic gas, H2. Sometimes hydrogen is placed in both Groups 1 and Groups of elements have similar properties.
The properties of some groups are so unique or important that the groups are referred to by special names. The elements in this group are called the noble gases. Noble gases seldom react with other elements. Noble gases have many uses, for example, they are used in neon signs Fig 2.
Group 1 is often referred to as the alkali metals, Group 2 as the alkaline earth metals, and Group 17 as the halogens. The two groups that are pulled out on the bottom of the periodic table in rows are called the lanthanide rare earth series top row and the actinide series bottom row. This document may be freely reproduced and distributed for non-profit educational purposes. Skip to main content. Search form Search. Join The Community Request new password. Main menu About this Site Table of Contents.
Atoms, Molecules, and Compounds. NGSS Performance Expectations: HS-PS Use the periodic table as a model to predict the relative properties of elements based on the patterns of electrons in the outermost energy level of atoms.
The content and activity in this topic will work towards building an understanding of the structure of atoms and how elements are organized on the periodic table. Chemical Structures The properties of elements and compounds are determined by their structures. Electrostatic Forces Electrostatic forces hold atoms in molecules. Determine how charged matter interacts. Properties of metals and nonmetals Metals Nonmetals Physical Properties Good conductor of heat and electricity Poor conductor of heat and electricity Malleable - can be beaten or deformed without cracking; pliable Brittle Ductile - can be made into wire Non-ductile Lustrous Not lustrous, may be opaque or transparent Solid at room temperature except Hg and a few other metals that are liquid at or near room temperature Solid, liquid, or gas at room temperature Chemical Properties Usually have valence electrons Usually have valence electrons Tend to lose valence electrons Tend to gain electrons.
Other Organizational Features of the Periodic Table There are other organizational features of the periodic table. Further Investigations. Table of Contents: Atoms, Molecules, and Compounds. Activity: Electrostatic Forces. Special Features:. Representative Image:. Further Investigations: What is an Invertebrate? Question Set: What is a Mammal? Further Investigations: What is a Mammal? Share and Connect. We invite you to share your thoughts, ask for help or read what other educators have to say by joining our community.
Partner Organizations. There are more than different types of atom - one for each element. Differences between the atoms give the elements their different chemical properties.
When enough atoms combine together we begin to get matter that we can see. This full stop is made from about 10 million million atoms in the phosphor of your computer screen. Only when lots of them join together can we see visible lumps of elements or compounds. Atoms can combine with atoms of the same element for example, oxygen, hydrogen or a lump of carbon.
Probably everything you see around you is some type of compound. When atoms of different kinds combine to form a compound, a new substance is created. New compounds do not have the same physical or chemical traits of the original elements. They have a new life of their own. Compounds are written with formulas showing which elements from the periodic table are combined. One very familiar compound is water. When two hydrogen atoms H 2 combine with one oxygen atom O , it makes the compound H 2 O, which we know as water.
All water molecules have this same combination of atoms. Water is not hydrogen or oxygen. You couldn't pour oxygen and hydrogen atoms on a fire and expect to put it out. But when they are bonded together as water molecules, they behave like water. A compound is a brand new substance with its own properties. The same elements can build very different compounds.
If you took those two hydrogen atoms and joined them to two oxygen atoms instead of one , you would wind up not with water but with H 2 O 2 , a very different compound called hydrogen peroxide - you wouldn't want to drink it! How do these compounds form? What holds the atoms in a molecule together?
The answer is that compounds are formed when elements are joined and held together by strong forces called chemical bonds.
These bonds involve the electrons that orbit the nucleus of the atom. Electrons are located in energy levels that occur at certain distances from the nucleus, called shells.
These shells can each carry a certain number of electrons for example, 2 in the first shell, 8 in the second, and so on. Atoms want to have their shells full with as many electrons as they can carry, and when their outermost shell isn't full, atoms try to bond with other atoms by giving up or gaining electrons.
Atoms with an almost-empty outer shell will want to give up electrons, while atoms with an almost-full outer shell will want to gain electrons in order to fill it up. There are two main types of bonds that hold most compounds together. Ionic bonds form when one atom gives up, or donates, an electron to another in order that both will have a full outer shell.
In doing so, the atoms are bonded and create a compound. But the reality is that we are made of extremely tiny building blocks, and there are more of them in each of us than there are kilograms in the Earth, stars in the observable Universe, or grains of sand in the entire Solar System. In fact, right now, if you take a deep breath and then exhale, by the time a year goes by, approximately one atom from that breath will wind up in every other person on Earth's lungs at any moment in time.
In other words, you probably have approximately one atom from Caesar's last breath in your lungs right now. Our bodies might appear to remain roughly the same on a year-to-year basis, but the fact is that we're actually expelling the atoms inside of us all the time:. Meanwhile, we're breathing air, drinking water, and eating plants and animals, and that brings new atoms into our bodies to replace the ones we're constantly losing.
Planet Earth is a roughly closed system as far as the atoms in our biosphere go, which means that, given enough time for things to sufficiently mix, these tiny, microscopic components of our world will inevitably spread wherever water and air are allowed to go. From macroscopic scales down to subatomic ones, the sizes of the fundamental particles play only a Every time you breathe in, you're breathing atoms of air that were once inside another human being.
Every time you take a drink of water, you're drinking water that was once inside another human being. And every bite of food you take consists of atoms that were inside another person. We all share the same planet, the same biosphere, and — at a fundamental level — even the same atoms. At an atomic level, we're all incredibly deeply connected.
Inside your body, right now, are hundreds of billions of atoms that were once inside each other human being on Earth. Throughout the generations and the aeons, those same atoms continue to make up everything: the atoms of the dinosaurs, the plants, the trilobites, and even the single-celled organisms that once dominated our planet are now inside you.
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