What Are 3 Types Of Elements That Makeup The Periodic Tble

CHEMISTRY I: ATOMS AND MOLECULES

Table of Contents

Atoms | Electrons and energy | Chemical Bonding | Chemical reactions and molecules

Learning Objectives | Terms | Review Questions | Links

Atoms | Back to Top

Most of the Universe consists of matter and energy . Energy is the capacity to do work. Matter has mass and occupies space. All matter is composed of bones elements that cannot be broken downward to substances with unlike chemical or physical properties. Elements are substances consisting of one type of atom , for example Carbon atoms make upwards diamond, and also graphite. Pure (24K) gold is equanimous of simply one type of cantlet, gilded atoms. Atoms are the smallest particle into which an element can be divided. The aboriginal Greek philosophers developed the concept of the atom, although they considered it the fundamental particle that could not exist broken down. Since the work of Enrico Fermi and his colleagues, we now know that the atom is divisible, often releasing tremendous energies equally in nuclear explosions or (in a controlled mode in) thermonuclear ability plants.

Subatomic particles were discovered during the 1800s. For our purposes we will concentrate merely on three of them, summarized in Tabular array 1. The proton is located in the eye (or nucleus ) of an atom, each cantlet has at to the lowest degree one proton. Protons have a charge of +i, and a mass of approximately i atomic mass unit (amu). Elements differ from each other in the number of protons they take, eastward.g. Hydrogen has 1 proton; Helium has ii.

The neutron also is located in the atomic nucleus (except in Hydrogen). The neutron has no accuse, and a mass of slightly over 1 amu. Some scientists propose the neutron is fabricated upwards of a proton and electron-like particle.

The electron is a very small particle located outside the nucleus. Because they motility at speeds near the speed of light the precise location of electrons is hard to pin down. Electrons occupy orbitals, or areas where they have a high statistical probability of occurring. The charge on an electron is -one. Its mass is negligible (approximately 1800 electrons are needed to equal the mass of one proton).

Table 1. Subatomic particles of use in biology.

Name	Charge	Location	Mass
Proton	+1	diminutive nucleus	1.6726 X 10-27 kg
Neutron	0	atomic nucleus	1.6750 10 10-27 kg
Electron	-1	electron orbital	9.1095 10 10-31 kg

The atomic number is the number of protons an atom has. It is characteristic and unique for each element. The atomic mass (also referred to equally the diminutive weight) is the number of protons and neutrons in an atom. Atoms of an element that have differing numbers of neutrons (but a abiding atomic number) are termed isotopes . Isotopes, shown in Figure 1 and Figure two, can be used to determine the nutrition of ancient peoples by determining proportions of isotopes in mummified or fossilized homo tissues. Biochemical pathways can exist deciphered by using isotopic tracers. The age of fossils and artifacts tin can be determined by using radioactive isotopes, either directly on the fossil (if it is immature plenty) or on the rocks that surround the fossil (for older fossils like dinosaurs). Isotopes are also the source of radiations used in medical diagnostic and handling procedures.

Effigy 1. Note that each of these isotopes of hydrogen has only one proton. Isotopes differ from each other in the number of neutrons, not in the number of protons. Image from Purves et al., Life: The Science of Biological science, quaternary Edition, by Sinauer Associates ( www.sinauer.com ) and WH Freeman ( www.whfreeman.com ), used with permission.

Some isotopes are radioisotopes, which spontaneously disuse, releasing radioactivity . Other isotopes are stable. Examples of radioisotopes are Carbon-14 (symbol ^fourteenC), and deuterium (also known as Hydrogen-2; ²H). Stable isotopes are ¹²C and ¹H.

Figure 2. Carbon has iii isotopes, of which carbon-12 and carbon-xiv are the most well known. Paradigm from Purves et al., Life: The Scientific discipline of Biology, fourth Edition, past Sinauer Associates ( www.sinauer.com ) and WH Freeman ( www.whfreeman.com ), used with permission.

The Periodic Tabular array of the Elements, a version of which is shown in Figure 3, provides a dandy deal of information about various elements. An on-line Periodic Table is bachelor by clicking here ,

Effigy 3. The Periodic Table of the Elements. Each Roman numeraled column on the label (at least the ones ending in A) tells united states of america how many electrons are in the outer crush of the atom. Each numbered row on the table tells us how many electron shells an cantlet has. Thus, Hydrogen, in cavalcade IA, row i has 1 electron in one shell. Phosphorous in column VA, row three has 5 electrons in its outer shell, and has three shells in total. Image from James M. Hardy's chemical science site at the University of Akron.

Electrons and free energy | Dorsum to Top

Electrons, considering they move so fast (approximately at the speed of light), seem to straddle the fence separating energy from matter. Albert Einstein developed his famous E=mcⁱⁱ equation relating thing and energy over a century ago. Because of his (and others) piece of work, we think of electrons both every bit particles of matter (having mass is a property of matter) and as units (or quanta) of free energy. When subjected to energy, electrons will acquire some of that energy, as shown in Figure 4.

Effigy 4. Excitation of an electron by energy, causing the electron to "bound" to some other electron (free energy) level known as the excited state. Paradigm from Purves et al., Life: The Scientific discipline of Biological science, quaternary Edition, past Sinauer Associates ( world wide web.sinauer.com ) and WH Freeman ( www.whfreeman.com ), used with permission.

An orbital is as well an surface area of space in which an electron volition be establish xc% of the time. Orbitals accept a variety of shapes. Each orbital has a characteristic energy country and a characteristic shape. The south orbital is spherical. Since each orbital can hold a maximum of two electrons, atomic numbers higher up 2 must make full the other orbitals. The p_x , p_y , and p_z orbitals are dumbbell shaped, forth the x, y, and z axes respectively. These orbital shapes are shown in Figure 5.

Energy levels (as well referred to every bit electron shells) are located a sure "altitude" from the nucleus. The major energy levels into which electrons fit, are (from the nucleus outward) Thousand, 50, M, and North. Sometimes these are numbered, with electron configurations being: 1due south ²twosouth ²2p ^one, (where the offset crush K is indicated with the number i, the second beat L with the number 2, etc.). This nomenclature tells us that for the atom mentioned in this paragraph, the first free energy level (beat out) has two electrons in its s orbital (the only orbital it can have), and second energy level has a maximum of two electrons in its due south orbital, plus one electron in its p orbital.

Figure 5. Geometry of orbitals. S-orbitals are spherical, p-orbitals are shaped like a dumbbell or effigy 8. Epitome from Purves et al., Life: The Science of Biology, fourth Edition, past Sinauer Assembly ( www.sinauer.com ) and WH Freeman ( www.whfreeman.com ), used with permission.

Chemic Bonding | Dorsum to Top

During the nineteenth century, chemists arranged the then-known elements according to chemical bonding, recognizing that 1 group (the far-off right column on the Periodic Table, referred to as the Inert Gases or Noble Gases) tended to occur in elemental form (in other words, not in a molecule with other elements). It was later determined that this group had outer electron shells containing two (as in the case of Helium) or 8 (Neon, Xenon, Radon, Krypton, etc.) electrons.

As a full general rule, for the atoms we are likely to meet in biological systems, atoms tend to gain or lose their outer electrons to achieve a Element of group 0 outer electron shell configuration of 2 or 8 electrons. The number of electrons that are gained or lost is feature for each chemical element, and ultimately determines the number and types of chemical bonds atoms of that element can form. Atomic diagrams for several atoms are shown in Figure 6.

Figure 6. Atomic diagrams illustrating the filling of the outer electron shells. Images from Purves et al., Life: The Science of Biology, 4th Edition, by Sinauer Assembly ( world wide web.sinauer.com ) and WH Freeman ( world wide web.whfreeman.com ), used with permission.

Ionic bonds are formed when atoms become ions past gaining or losing electrons. Chlorine is in a group of elements having vii electrons in their outer shells (see Figure vi). Members of this group tend to proceeds one electron, acquiring a charge of -i. Sodium is in another group with elements having one electron in their outer shells. Members of this group tend to lose that outer electron, acquiring a accuse of +1. Oppositely charged ions are attracted to each other, thus Cl^- (the symbolic representation of the chloride ion) and Na⁺ (the symbol for the sodium ion, using the Greek word natrium) form an ionic bail, condign the molecule sodium chloride, shown in Effigy 7. Ionic bonds generally grade between elements in Group I (having one electron in their outer shell) and Group VIIa (having seven electrons in their outer shell). Such bonds are relatively weak, and tend to disassociate in water, producing solutions that have both Na and Cl ions.

Figure 7. TOP: Formation of a crystal of sodium chloride. Each positively charged sodium ion is surropunded by six negatively charged chloride ions; likewise each negatively charged chloride ion is surrounded by six positively charged sodium ions. The overall effect is electrical neutrality. Image from Purves et al., Life: The Science of Biology, quaternary Edition, past Sinauer Associates ( www.sinauer.com ) and WH Freeman ( www.whfreeman.com ), used with permission. BOTTOM: Table Salt Crystal (SEM x625). This paradigm is copyright Dennis Kunkel at www.DennisKunkel.com , used with permission.

Covalent bonds form when atoms share electrons. Since electrons move very fast they can be shared, effectively filling or emptying the outer shells of the atoms involved in the bond. Such bonds are referred to equally electron-sharing bonds. An analogy tin be made to child custody: the children are similar electrons, and tend to spend some fourth dimension with one parent and the residue of their fourth dimension with the other parent. In a covalent bail, the electron clouds surrounding the atomic nuclei overlap, as shown in Figure viii.

Figure 8. Germination of a covalent bail between two Hydrogen atoims. Prototype from Purves et al., Life: The Scientific discipline of Biological science, fourth Edition, past Sinauer Assembly ( world wide web.sinauer.com ) and WH Freeman ( www.whfreeman.com ), used with permission.

Carbon (C) is in Group IVa, significant it has four electrons in its outer shell. Thus to go a "happy atom", Carbon can either gain or lose iv electrons. By sharing the electrons with other atoms, Carbon can go a happy atom,. alternately filling and emptying its outer shell, equally with the iv hydrogens shown in Figure 9.

Effigy nine. Formation of covalent bonds in methyl hydride. Carbon needs to share four electrons, in effect information technology has 4 slots. Each hydrogen provides an electron to each of these slots. At the same time each hydrogen needs to fill up one slot, which is done by sharing an electron with the carbon. Paradigm from Purves et al., Life: The Science of Biology, 4th Edition, by Sinauer Associates ( www.sinauer.com ) and WH Freeman ( www.whfreeman.com ), used with permission.

The molecule methyl hydride (chemical formula CH₄) has iv covalent bonds, one between Carbon and each of the four Hydrogens. Carbon contributes an electron, and Hydrogen contributes an electron. The sharing of a single electron pair is termed a single bond. When two pairs of electrons are shared, a double bond results, equally in carbon dioxide. Triple bonds are known, wherein 3 pairs (six electrons total) are shared as in acetylene gas or nitrogen gas. The types of covalent bonds are shown in Effigy 10.

Figure 10. Ways of representing covalent bonds. Paradigm from Purves et al., Life: The Science of Biology, fourth Edition, by Sinauer Assembly ( www.sinauer.com ) and WH Freeman ( world wide web.whfreeman.com ), used with permission.

Sometimes electrons tend to spend more time with one atom in the bond than with the other. In such cases a polar covalent bond develops. Water (H₂O) is an case. Since the electrons spend so much time with the oxygen (oxygen having a greater electronegativity, or electron affinity) that end of the molecule acquires a slightly negative charge. Conversely, the loss of the electrons from the hydrogen end leaves a slightly positive charge. The water molecule is thus polar, having positive and negative sides.

Hydrogen bonds , as shown in Effigy eleven, event from the weak electrical allure betwixt the positive end of one molecule and the negative end of another. Individually these bonds are very weak, although taken in a large enough quantity, the result is strong enough to agree molecules together or in a three-dimensional shape.

Effigy 11. Height: Formation of a hydrogen bond between the hydrogen side of ane water molecule and the oxygen side of another h2o molecule. Lesser: The presence of polar areas in the amino acids that makeup a protein allows for hydrogen bonds to form, giving the molecule a iii-dimensional shape that is frequently vital to that protein's proper functioning. Images from Purves et al., Life: The Science of Biology, 4th Edition, by Sinauer Assembly ( www.sinauer.com ) and WH Freeman ( world wide web.whfreeman.com ), used with permission.

Chemical reactions and molecules | Back to Top

Molecules are compounds in which the elements are in definite, fixed ratios, as seen in Effigy 12. Those atoms are held together usually past 1 of the three types of chemical bonds discussed above. For instance: water, glucose, ATP. Mixtures are compounds with variable formulas/ratios of their components. For example: soil. Molecular formulas are an expression in the simplest whole-number terms of the composition of a substance. For example, the sugar glucose has 6 Carbons, 12 hydrogens, and vi oxygens per repeating structural unit. The formula is written C₆H₁₂O_half-dozen.

Figure 12. Determination of molecular weights by addition of the weights of the atoms that make up the molecule. Image from Purves et al., Life: The Science of Biology, quaternary Edition, by Sinauer Assembly ( www.sinauer.com ) and WH Freeman ( www.whfreeman.com ), used with permission.

Chemical reactions occur in nature, and some also tin can be performed in a laboratory setting. Ane such reaction is diagrammed in Figure 13. Chemical equations are linear representations of how these reactions occur. Combination reactions occur when two separate reactants are bonded together, due east.g. A + B -----> AB. Disassociation reactions occur when a compound is broken into ii products, due east.g. AB -----> A + B.

Figure 13. Diagram of a chemical reaction: the combustion of propane with oxygen, resulting in carbon dioxide, water, and free energy (equally rut and light). This chemical reaction takes place in a camping stove every bit well as in certain welding torches. Image from Purves et al., Life: The Science of Biology, 4th Edition, past Sinauer Associates ( www.sinauer.com ) and WH Freeman ( world wide web.whfreeman.com ), used with permission.

Biological systems, while unique to each species, are based on the chemical bonding properties of carbon. Major organic chemicals (those associated with or formed by the actions of living things) unremarkably include some ratios of the post-obit elements: C, H, Northward, O, P, Due south.

Learning Objectives | Back to Top

• All forms of matter are composed of one or more elements. Be able to list the major elements in living things.
• Depict how protons, electrons, and neutrons are arranged into atoms and ions.
• Define the terms atomic number and diminutive mass and be able to depict their sugnificance.
• Atoms with the aforementioned atomic number simply a different mass number are isotopes. List the isotopes of hydrogen and of carbon.
• Be able to describe radioisotopes and list three ways they are used in biology.
• The spousal relationship between the electron structures of atoms is known as the chemical bond. Be able to listing and depict the iii types of chemical bonds found in living things.
• Be able to describe the distribution of electrons in the space around the nucleus of an atom.
• An atom tends to react with other atoms when its outermost shell is but partly filled with electrons. Be able to hash out why this happens.
• Be able to ascertain the two types of ions and describe thow ionic bonds class between positive and negative ions.
• In a covalent bond, atoms share electrons. List several elements that tend to grade covalent bonds.
• Distinguish betwixt a nonpolar covalent bail and a polar covalent bail and give an example of each.
• Define hydrogen bond and describe weather condition under which hydrogen bonds form and cite one example.
• Explain what is meant by the polarity of the h2o molecule, and how the polarity of water molecules allows them to interact with one another.

Terms | Back to Top

atom	atomic mass	diminutive number	covalent bonds	electron	elements
energy	glucose	hydrogen bonds	ions	ionic bonds	isotopes
matter	molecules	neutron	nucleus	polar covalent bail	proton
radioactivity

Review Questions | Dorsum to Top

1. Which of these is not a subatomic particle? a) proton; b) ion; c) neutron; d) electron
2. The outermost electron trounce of every Noble gas element (except Helium) has ___ electrons. a) 1; b) ii; c) 4; d) vi; e) 8
3. An organic molecule is likely to contain all of these elements except ___. a) C; b) H; c) O; d) Ne; e) Due north
4. The chemic bail between h2o molecules is a ___ bond. a) ionic; b) polar covalent; c) nonpolar covalent; d) hydrogen
5. A solution with a pH of seven has ___ times more H ions than a solutrion of pH 9. a) ii; b) 100; c) 1000; d) ix; eastward) 90
6. The type of chemical bond formed when electrons are shared betwixt atoms is a ___ bond. a) ionic; b) covalent; c) hydrogen
7. The blazon of chemical bail formed when oppositely charged particles are attrached to each other is a ___ bond. a) ionic; b) covalent; c) hydrogen
8. Electrons occupy volumes of infinite known as ___. a) nuclei; b) periods; c) wavelengths; d) orbitals
9. Carbon has an atomic number of half-dozen. This ways it has ___. a) six protons; b) half dozen neutrons; c) half-dozen protons plus six neutrons; d) six neuitrons and six electrons
10. Each of the isotopes of hydrogen has ___ proton(s). a) iii; b) i; c) 2; d) 92; eastward) ane/2
11. A molecule is ___. a) a mixture of diverse components that tin vary; b) a combination of many atoms that will take different ratios; c) a combination of 1 or more than atoms that will have a fixed ratio of its components; d) more than of import in a chemistry grade than in a biology class

Links | Back to Height

• Chemicool A colorful and piece of cake to apply Periodic Tabular array. More data virtually elements than most of us would want.
• WebElements Much more detailed Periodic Table. Even more than information about those pesky elements! If this site is busy there are a series of mirror sites.
• The Periodic Tabular array This site, adult by the Fossil Company, provides a version of the Periodic Tabular array where moving the mouse cursor over an chemical element on the table brings up information about electron shells, mass, etc. A very prissy site.
• James Chiliad. Hardy'due south Chemistry Site (U of Akron). Powerpoint slides (that run over the Web) and a series of animations...a must meet!
• Diamond Images of diamond and graphite crystal structure.

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Text ©1992, 1994, 1997, 1998, 1999, 2000, 2001, 2002, 2007, by Thousand.J. Farabee, all rights reserved. Utilize for educational purposes is encouraged.

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