[ Ссылка ]
What Is An Atom? An atom is the smallest constituent unit of ordinary matter, that has the properties of a chemical element. Every solid, liquid, gas, and plasma is composed of neutral or ionized atoms. Atoms are very small; (a ten-billionth of a meter, in the short scale). However, atoms do not have well-defined boundaries, and there are different ways to define their size that give different but close values.
Every atom is composed of a nucleus and one or more electrons bound to the nucleus. The nucleus is made of one or more protons and typically a similar number of neutrons (none in hydrogen-1). Protons and neutrons are called nucleons. More than 99.94% of an atom's mass is in the nucleus. The protons have a positive electric charge, the electrons have a negative electric charge, and the neutrons have no electric charge. If the number of protons and electrons are equal, that atom is electrically neutral. If an atom has more or fewer electrons than protons, then it has an overall negative or positive charge, respectively, and it is called an ion.
The electrons of an atom are attracted to the protons in an atomic nucleus by this electromagnetic force.
![](https://i.ytimg.com/vi/4huWkpzg0T4/maxresdefault.jpg)