Atom | Definition, Structure, History, Examples, Diagram, & Facts
网页2024年8月17日 · The single most important characteristic of an atom is its atomic number (usually denoted by the letter Z), which is defined as the number of units of positive charge (protons) in the nucleus. For example, if an atom has a Z of 6, it is carbon, while a Z of 92 corresponds to uranium.
Atom - Wikipedia
网页An atom consists of a nucleus of protons and generally neutrons, surrounded by an electromagnetically bound swarm of electrons. The chemical elements are distinguished from each other by the number of protons that are in their atoms. For example, any atom that contains 11 protons is sodium, and any atom that contains 29 protons is copper.
Atomic number, atomic mass, and isotopes (article) | Khan Academy
网页Fundamental properties of atoms including atomic number and atomic mass. The atomic number is the number of protons in an atom, and isotopes have the same atomic number but differ in the number of neutrons.
Atomic number | Definition & Facts | Britannica
网页Atomic number, the number of a chemical element in the periodic system, whereby the elements are arranged in order of increasing number of protons in the nucleus. Accordingly, the number of protons, which is always equal to the number of electrons in a neutral atom, is also the atomic number.
1.3: Atomic Structure and Symbolism - Chemistry LibreTexts
网页2018年9月11日 · An atom consists of a small, positively charged nucleus surrounded by electrons. The nucleus contains protons and neutrons; its diameter is about 100,000 times smaller than that of the atom. The mass of one atom is usually expressed in atomic mass units (amu), which is referred to as the atomic mass.
2.2: Atomic Structure - Chemistry LibreTexts
网页2021年5月18日 · Chemistry is based on the modern atomic theory, which states that all matter is composed of atoms. Atoms themselves are composed of protons, neutrons, and electrons. Each element has its own atomic number, which is equal to the number of protons in its nucleus. Isotopes of an element contain different numbers of neutrons.
Basic concept and structure of an atom | Britannica
网页atom, Smallest unit into which matter can be divided and still retain the characteristic properties of an element. The word derives from the Greek atomos (“indivisible”), and the atom was believed to be indivisible until the early 20th century, when electrons and the nucleus were discovered.
What Is an Atom? Atom Definition - Science Notes and Projects
网页2023年11月19日 · An atom is the smallest unit of matter that forms a chemical element and cannot be divided using any chemical means. Every solid, liquid, gas, and plasma consists of neutral or ionized atoms. An atom consists of a nucleus of protons and neutrons that is surrounded by electrons.
Atom: Definition, Structure & Parts with Labeled Diagram
网页2024年2月29日 · Atoms are tiny particles that form the basic building blocks of all matter in the universe, whether solid, liquid, or gas. All living organisms and nonliving objects found on Earth are made of trillions and trillions of atoms. The smaller particles that make up an atom are known as subatomic particles. Parts of an Atom Diagram.
Atoms: What are they and how do they build the elements?
网页2022年10月30日 · The word "atom" comes from the Greek "atomos", meaning something that is uncuttable, or which cannot be split. Once upon a time, early scientists and philosophers thought that this was indeed the...
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