Each element is made of atoms, each with a constant number of protons and unique properties. A total of elements have been defined; however, only 92 occur naturally, and fewer than 30 are found in living cells. The remaining 26 elements are unstable and, therefore, do not exist for very long or are theoretical and have yet to be detected. Each element is designated by its chemical symbol such as H, N, O, C, and Na , and possesses unique properties. These unique properties allow elements to combine and to bond with each other in specific ways.
An atom is the smallest component of an element that retains all of the chemical properties of that element. For example, one hydrogen atom has all of the properties of the element hydrogen, such as it exists as a gas at room temperature, and it bonds with oxygen to create a water molecule. Hydrogen atoms cannot be broken down into anything smaller while still retaining the properties of hydrogen.
If a hydrogen atom were broken down into subatomic particles, it would no longer have the properties of hydrogen. At the most basic level, all organisms are made of a combination of elements.
They contain atoms that combine together to form molecules. In multicellular organisms, such as animals, molecules can interact to form cells that combine to form tissues, which make up organs.
These combinations continue until entire multicellular organisms are formed. All atoms contain protons , electrons , and neutrons.
The only exception is hydrogen H , which is made of one proton and one electron. An electron is a negatively charged particle that travels in the space around the nucleus. In other words, it resides outside of the nucleus. It has a negligible mass and has a charge of —1. Neutrons, like protons, reside in the nucleus of an atom. They have a mass of 1 and no charge. The positive protons and negative electrons charges balance each other in a neutral atom, which has a net zero charge.
Because protons and neutrons each have a mass of 1, the mass of an atom is equal to the number of protons and neutrons of that atom. The number of electrons does not factor into the overall mass, because their mass is so small. As stated earlier, each element has its own unique properties. Each contains a different number of protons and neutrons, giving it its own atomic number and mass number.
The atomic number of an element is equal to the number of protons that element contains. The mass number , or atomic mass, is the number of protons plus the number of neutrons of that element. Therefore, it is possible to determine the number of neutrons by subtracting the atomic number from the mass number.
These numbers provide information about the elements and how they will react when combined. Different elements have different melting and boiling points, and are in different states liquid, solid, or gas at room temperature. They also combine in different ways. Some form specific types of bonds, whereas others do not. How they combine is based on the number of electrons present.
Because of these characteristics, the elements are arranged into the periodic table of elements , a chart of the elements that includes the atomic number and relative atomic mass of each element. The periodic table also provides key information about the properties of elements —often indicated by color-coding. The arrangement of the table also shows how the electrons in each element are organized and provides important details about how atoms will react with each other to form molecules.
Isotopes are different forms of the same element that have the same number of protons, but a different number of neutrons. Some elements, such as carbon, potassium, and uranium, have naturally occurring isotopes. Carbon, the most common isotope of carbon, contains six protons and six neutrons. Therefore, it has a mass number of 12 six protons and six neutrons and an atomic number of 6 which makes it carbon. Carbon contains six protons and eight neutrons.
Therefore, it has a mass number of 14 six protons and eight neutrons and an atomic number of 6, meaning it is still the element carbon.
Atoms exist around us--in the air, the Earth and in living things. Naturally occurring elements, such as oxygen, gold and sodium, are atoms of different forms, and each with a unique number of electrons, protons and neutrons. The protons and neutrons make up the central core of the atom, while the electrons circle the core in defined orbitals called energy levels. Electrons group themselves in pairs in their energy levels.
To calculate the number of electrons allowed in any energy level, find the square of the number representing the energy level and multiply it by two.
Using this formula, atoms can have two electrons in their first energy level, eight in the second, and eighteen in their third. The quantity of electrons at each level grows as the number of the energy level increases. Electrons form pairs at the lowest energy level first and work their way outward. However, there are three primary types of chemical bonds that you'll see most often: covalent, metallic, and ionic. Covalent bonds form between nonmetallic materials.
In a covalent bond, electrons are shared between atoms. The bonds between the two hydrogen atoms and the oxygen atom in a molecule of water are covalent bonds. As its name implies, a metallic bond occurs between metallic substances. The valence atoms in metals move freely and thus form bonds easily. This is what makes metals good conductors of heat and electricity.
Ionic bonds form between a metal and a nonmetal substance. In an ionic bond, electrons get transferred from the metal to the nonmetal substance. An example of a compound formed with ionic bonds is sodium chloride NaCl , otherwise known as table salt! Are you ready to experiment with molecules? Be sure to explore the following activities with a friend or family member:. Hi, melyssa! Thanks for the compliment! That is a question we can't answer for you, Swag.
We do encourage you to do your own research and see what you can find out. It's definitely a topic worth exploring! Good luck, Wonder Friend! We don't encourage anyone to try that because they could burn themselves. We hope you are ok! Good question! Good question, Zachary! You should submit that to our Wonder Bank!
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Thanks for your patience. Drag a word to its definition. You have answered 0 of 3 questions correctly and your score is:. Want to add a little wonder to your website? Help spread the wonder of families learning together. We sent you SMS, for complete subscription please reply. Follow Twitter Instagram Facebook. Why do atoms form molecules?
What is a compound? What is a covalent bond? This means their valence shell becomes full. By achieving an octet or duet, they achieve a noble gas configuration, which makes the atoms stable. Molecules are composed of nonmetal atoms which share valence electrons in covalent bonds so that all of the bonded atoms have an octet or duet. This makes the atoms more stable than existing alone, which is why in nature nonmetals are not generally found as individual elements.
It is important to note that atoms bond in order to become stable. For example, they don't know that we need oxygen gas or water to live. The atoms of these molecules share valence electrons in order to achieve an octet or duet, which makes them stable. Hydrogen atoms have one valence electron, which they share to achieve a duet of valence elelctrons. The bond is the area of overlap.
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