单原子和多原子之间的差异

Monatomic vs Polyatomic

The number ofatomspresent in a particularionor amoleculeis what contributes to the difference between monatomic and polyatomic. The two words “mono” and “poly” give the general idea about the molecule; “mono” means “single” and “poly” means “many.” Monatomic refers to the ions or molecules having a single atom. Polyatomic refers to the molecules or ions having two or more atoms. There are so many physical and chemical differences between monatomic and polyatomic due to the difference in number of atoms. Generally monatomic chemical elements are less abundant compared to the existence of polyatomic molecules.

What is Monatomic?

The word monatomic derives from two words “mono” and “atomic,” giving the meaning of “single atom.” Monatomic chemical species contain only one atom and they are stable even if they exist alone. This can be applied to gases and ions. Most of thenoble gases作为单一化学物种存在。

Monatomic ions:These ions are formed by losing (positive ions) or gaining (negative ions)electrons.

Positive ions:Na⁺, K⁺，Ca2+，Al³⁺

Negative ions:Cl^–, S^2-，br^–, F^–

Monatomic molecules:高贵的气体属于这一类，它们非常稳定。因此，化学不活跃。

什么是多原子？

The word polyatomic derives from two words “poly” and “atomic,” meansmany atoms. It can be homogeneous atoms (O₂, Hg₂²⁺, O₃, O₂^2-) or a combination of heterogeneous atoms (CN^–, H₂SO₄, ClO₃^–). Most of the molecules and ions exist as polyatomic nature.

多原子离子：“Molecular ions” is another name for polyatomic ions. Most of the polyatomic ions are eithercovalently bonded化学物种或metalliccomplexes.

Positive ions:NH₄⁺, H₃O⁺, PH₄⁺

Negative ions:CrO₄^2-，co₃^2-, CH₃COO^–, SO₄^2-, NO₃^–

多原子分子：They are the molecules with two or more atoms. They do not have a positive or negative charge. In other words, these molecules are electrically neutral. (H₂SO₄, CH₃COOH, Na₂CO₃, NaCl, C₂H₄)

What is the difference between Monatomic and Polyatomic?

• Number of atoms:

• Monatomic chemical elements containonly one atom.

• Polyatomic chemical compounds havetwo or more atoms.

• State:

• Monatomic chemical species can be ions or inert gases.

• Some polyatomic species are ions and some are molecules.

• Properties

• Most of the monatomic ions are stable in water.

•单原子分子非常稳定；因此，化学不活跃。

• Most of the polyatomic ions are either covalently bonded or metallic complexes.

• Polyatomic molecules are electrically neutral.

•单原子和多原子的示例：

• Examples for元素ions是na⁺，CA²⁺, K⁺, Al³⁺and Fe³⁺.

• Examples for元素molecules是高贵的气体。它们是氦（He），霓虹灯（NE），氩（AR），Krypton（kr），Xenon（Xe）和Radon（Ra）。

• Examples forpolyatomic ionsare CrO₄²-, CO₃^2-, NH₄⁺, H₃O⁺.

• Examples forpolyatomic moleculesare KCl, KBrO₃, C₆H₅COOH.

• 尺寸：

• The size of the monatomic chemical species differs according to the way they form. For example, when positive ions are formed their sizes decreases and when negative ions are formed, the size increases than the original atom. Noble gases have the smallest size compared to the other elements in their period in the periodic table.

• When polyatomic chemical compounds are formed, the size of the polyatomic ion or the polyatomic molecule becomes bigger than all the original atoms in the compound. Because, two or more atoms combine to form a polyatomic ion /molecule.

• Shape:

• Generally monatomic molecules and ions are spherical in their geometry.

• The geometry of the polyatomic chemical species varies depending on the number of molecules and the lone pairs present in the molecule. As the number of atoms increases more complex structures are formed to attain stability.

Images Courtesy:

1. ArgonbyGreg Robson(CC BY-SA 2.0 uk)
2. Ammonium通过Wikicommons（公共领域）