Chemical elements
Chemical elements are the fundamental substances that cannot be broken down into simpler substances through chemical means. Each element consists of a unique type of atom defined by its atomic number, which indicates the number of protons, and its atomic mass, which reflects the total count of protons and neutrons. There are 118 known chemical elements, with 94 occurring naturally on Earth, and they are categorized into three main types: metals, nonmetals, and metalloids. These elements can combine to form various chemical compounds, such as ionic and covalent compounds or alloys.
The origins of these elements trace back to the Big Bang, where they began forming shortly after the universe's inception. The periodic table serves as a systematic representation of these elements, arranged by increasing atomic number, and was significantly advanced by Dmitri Mendeleev in the 19th century. Understanding the properties and behaviors of these elements has been pivotal in the development of chemistry, particularly through the contributions of early alchemists and modern chemists, who have established foundational concepts in atomic theory and chemical reactions. Each chemical element is denoted by a unique symbol, facilitating easy reference and study.
Chemical elements
A chemical element is the simplest form of a substance and cannot be broken into smaller substances by chemical means. A chemical element is made of a single type of atom with varying properties. Each element is identified by its atomic number, or proton count, and its atomic mass, or proton and neutron count. Known chemical elements in the universe total 118. Each has its own unique symbol, notated on the periodic table of elements. Of the 118, only 94 occur naturally on Earth. Three types of chemical elements exist: metals, nonmetals, and metalloids. Chemical elements can be combined to form chemical compounds.
History
The Big Bang Theory is the most accepted explanation for the origin of the universe. It states that the universe and all its components resulted from a huge explosion that took place about thirteen billion years ago. Chemical elements began to form within seconds of this explosion. Atoms, the smallest part of all matter, made up these elements. At the center of an atom is a nucleus. A nucleus consists of protons, which have a positive charge, and neutrons, which do not have a charge. Electrons, which have a negative charge, orbit the nucleus. The number of protons, neutrons, and electrons determines the structure of a chemical element.
Hydrogen was the first element to be created and remains the most abundant element in the universe. The nucleus of a hydrogen atom contains one proton, therefore, its atomic number is one. Eventually, the heat of the explosion fused two hydrogen nuclei together to form helium, another prevalent element. Over time, more elements materialized and formed the solar system. Each planet in the solar system harbors different types and levels of elements. For instance, hydrogen and helium mainly compose Jupiter and Saturn. Hydrogen and helium make up about 98 percent of all atoms in the universe. Oxygen is the most abundant element on Earth.
Origins of Chemistry
Early humans gradually became aware of the various elements by accidental discovery. Fire is one of the earliest human experiences with chemical reactions. Pottery and baking were other chemical reactions that resulted from early human experimentation. People did not study the nature of chemical changes for many centuries. Philosophers of Ancient Greece theorized the existence of atoms, but they had no evidence to support their theories. During the age of alchemy, alchemists mostly learned their science through trial and error. Their experiments did not reveal the structure of chemical reactions, but it did help to improve antiquated theories of science and medicine. Modern chemistry emerged many centuries later.
Chemists began studying atomic theory in greater depth in the seventeenth century. French chemist Antoine-Laurent Lavoisier was a major figure in modern chemistry. He discovered thirty elements and was the first to understand the chemical makeup of water. Lavoisier also established a systematic language of chemistry still used today. In 1808, English chemist John Dalton published A New System of Chemical Philosophy, which concluded that individual elements were composed of the same number of atoms and therefore had the same atomic mass. Atomic mass became an important stepping stone to the advancement of chemistry, allowing scientists to theorize the relative weight of elements. Chemists also began exploring the potential of chemical compounds. As scientists continued to identify elements and determine their characteristics, many sought a means to organize this information, leading to the formation of the periodic table of elements.
Periodic Table
The periodic table of elements lists 118 chemical elements. It arranges the elements according to their chemical properties and atomic number. In 1871, Dmitri Mendeleev developed the modern periodic table, which originally arranged elements by atomic mass. When the structure of atoms came to be understood in the twentieth century, the table was arranged to reflect the increasing order of an element's atomic proton number, rather than its overall atomic mass.
The periodic table consists of chemical elements displayed in a grid, consisting of eighteen columns and seven rows, with two more rows below that. The rows of the table are called periods. The columns are called groups. The chemicals are arranged in ascending order by atomic number. Each element has a symbol, such as "He" for helium or "Ca" for calcium. These symbols on the grid have their atomic number displayed directly above them—and in some tables, the atomic mass directly below them. Elements with similar properties such as chemical bonds are in the same group. Elements with similar numbers of electron shells are in the same period.
Chemical Groups
The chemical elements are generally categorized as metals, nonmetals, and metalloids. Most of the elements are metals. Metals are good conductors of heat, malleable (capable of being manipulated), and solid at room temperature. Nonmetal elements are not good conductors of heat and are not malleable. These elements are usually gaseous or liquid at room temperature. Metalloids are similar to nonmetals, but they can be good heat conductors. On most periodic tables, a jagged line separates metals and nonmetals. The metals are to the left of the line, and the nonmetals are to the right. The elements touching the line are considered metalloids.
Several things can happen when combining different elements. When metals react with nonmetals, they form ionic compounds. Ionic compounds are solids and have high melting points. When nonmetals combine with each other, they form covalent compounds. Covalent compounds can be solids, liquids, or gases, and they have a lower melting point. Combining two or more metals forms an alloy. Examples of alloys include steel (iron and carbon) and bronze (copper and tin). Alloys are usually stronger than the metals from which they are made.
Bibliography
Boudreaux, Kevin A. "Metals, Metalloids, and Nonmetals." Angelo State University. Angelo State University. Web. 9 Dec. 2014. http://www.angelo.edu/faculty/kboudrea/periodic/physical‗metals.htm
Boudreaux, Kevin A. "Naturally-Occurring and Synthetic Elements." Angelo State University. Angelo State University. Web. 9 Dec. 2014. http://www.angelo.edu/faculty/kboudrea/periodic/physical‗natural.htm
"Elements, Compounds, and Mixtures." Purdue University College of Science. Purdue University. Web. 9 Dec. 2014. http://chemed.chem.purdue.edu/genchem/topicreview/bp/ch2/mixframe.html
Holden, Norman E. "History of the Origin of the Chemical Elements and Their Discoverers." National Nuclear Data Center. National Nuclear Data Center. Web. 9 Dec. 2014. http://www.nndc.bnl.gov/content/origindc.pdf
Krebs, Robert E. The History and Use of Our Earth's Chemical Element. Santa Barbara: Greenwood Publishing Group, 2006. 1–31. Print.
"Planetary Size and Density." Outer Planets. Laboratory for Atmospheric and Space Physics, University of Colorado at Boulder. Web. 9 Dec. 2014. http://lasp.colorado.edu/education/outerplanets/giantplanets‗interiors.php
Remick, Kaleigh, et al. "The Elements of Life: A Biocentric Tour of the Periodic Table." Advanced Microbial Physiology, 30 Jan. 2023, doi: 10.1016/bs.ampbs.2022.11.001. Accessed 13 Nov. 2024.