Atoms

What is an atom?

It’s the tiniest unit of matter with chemical properties. Atoms do not exist in isolation; rather, they combine to form ions and molecules, which then combine in large numbers to form the matter that we see, feel, and touch.

Laws of chemical combination:

Antoine L. Lavoisier laid the foundation of chemical sciences by establishing two important laws of chemical combination.

• Law of conservation of mass: It states that mass can neither be created nor destroyed in a chemical reaction.
• Law of constant proportions: It states that in a chemical substance the elements are always present in definite proportions by mass.

Dalton’s atomic theory

• Dalton picked up the idea of divisibility of matter and said that the smallest particles of matter are atoms. 
• His theory was based on the laws of chemical combination and provided an explanation for the law of conservation of mass and the law of definite proportions.
• According to Dalton’s atomic theory, all matter, whether an element, a compound or a mixture is composed of small particles called atoms. 
• The postulates of this theory may be stated as follows:

• All matter is made up of very tiny particles called atoms, which participate in chemical reactions. 
• Atoms are indivisible particles, which cannot be created or destroyed in a chemical reaction. 
• Atoms of a given element are identical in mass and chemical properties. 
• Atoms of different elements have different masses and chemical properties. 
• Atoms combine in the ratio of small whole numbers to form compounds. 
• The relative number and kinds of atoms are constant in a given compound.

Atom: 

Atoms are the building blocks of all matter. Our entire world is made up of atoms.

• Particles of most components can’t exist autonomously.
• Atoms form molecules and ions. These molecules or ions aggregate in large numbers to form the matter.

• Atomic radius is measured in nanometres. 1 m = 109 nm

Table: Relative Sizes of different things

Symbols of atoms of different elements:

• In the beginning, the names of elements were derived from the name of the place where they were found for the first time. For example, the name copper was taken from Cyprus. 
• A few names were taken from explicit tones. For instance, gold was taken from the English word importance yellow.
• IUPAC (International Union of Pure and Applied Chemistry) is an international scientific organisation which approves names of elements, symbols and units. 
• Many of the symbols are the first one or two letters of the element’s name in English.
• The first letter of a symbol is always written as a capital letter (uppercase) and the second letter as a small letter (lowercase).
• Symbols of some elements are formed from the first letter of the name and a letter, appearing later in the name. Examples are: (1) Cl for chlorine, (2) zinc-Zn for Zinc.
• Other symbols have been taken from the names of elements in Latin, German or Greek. For example, the symbol of iron is Fe from its Latin name ferrum, sodium is Na from natrium, potassium is K from kalium. 

Atomic mass:

According to Dalton’s atomic theory, each element had a characteristic atomic mass. In 1961, an all around acknowledged nuclear mass unit framework was embraced and carbon-12 isotope was picked as the standard reference for estimating nuclear masses.

One nuclear mass unit is a mass unit equivalent to precisely one-twelfth (1/twelfth) the mass of one iota of carbon-12. The overall nuclear mass

of the atom of an element is defined as the average mass of the atom, as compared to 1/12th the mass of one carbon-12 atom.

Ion: Compounds composed of metals and nonmetals contain charged species. The charged species are known as ions.

• Particles might comprise a solitary charged iota or a gathering of molecules that have a net charge on them.
• An ion can be negatively or positively charged.

• A negatively charged ion is called an ‘anion’ and the positively charged ion, a ‘cation’. 
• Sodium chloride (NaCl) has positively charged sodium ions (Na+) and negatively charged chloride ions (Cl–).

• A group of atoms carrying a charge is known as a polyatomic ion. 

Conclusion :

An atom is made up of two parts: 

• A nucleus, made up of 2 types of particles called protons and neutrons, lies at the core of an atom. 
• The electrical charge of protons is positive. The atom’s element is defined by the amount of protons in its nucleus. 
• Neutrons are similar to protons in size but do not have a charge. 
• Electrons, which are far smaller than protons or neutrons, have such a negative electrical charge, travel at almost the speed of light, and encircle the nucleus at precise distances, which are determined by their energy.