Atom

1) Definition

An atom is a particle of matter that uniquely defines achemical element. An atom consists of a central nucleus that is usually surrounded by one or more electrons. Each electron is negatively charged. 

The nucleus is positively charged, and contains one or more relatively heavy particles known as protons and neutrons.

2) Fission

When a nucleus fissions, it splits into several smaller fragments. These fragments, or fission products, are about equal to half the original mass. 

Two or three neutrons are also emitted.

3) Radioactive decay

Many nuclei are radioactive. This means they are unstable, and will eventually decay by emitting a particle, transforming 

the nucleus into another nucleus, or into a lower energy state.

There are three main types of radiation

    Alpha radiation

    Beta radiation

    Gamma radiation

4) Nucleosynthesis

A star's energy comes from the combining of light elements into heavier elements in a process known as fusion, or "nuclear burning".

 It is generally believed that most of the elements in the universe heavier than helium are created, or synthesized, 

in stars when lighter nuclei fuse to make heavier nuclei. The process is called nucleosynthesis.

Definition

An atom is a particle of matter that uniquely defines a chemical element. An atom consists of a central nucleus that is usually surrounded by one or more electrons. Each electron is negatively charged. 

The nucleus is positively charged, and contains one or more relatively heavy particles known as protons and neutrons.

Fission

During a nucleus fissions, an atom splits into several smaller fragments. These fragments, or fission products, are about equal to half the original mass. 

Two or three neutrons are also emitted.

Radioactive decay

Many nuclei are radioactive. This means they are unstable, and will eventually decay by emitting a particle, transforming the nucleus into another nucleus, or into a lower energy state.

There are three main types of radiation

•     Alpha radiation
•     Beta radiation
•     Gamma radiation

Nucleosynthesis

A star's energy comes from the combining of light elements into heavier elements in a process known as fusion, or "nuclear burning".

It is generally believed that most of the elements in the universe heavier than helium are created, or synthesized, in stars when lighter nuclei fuse to make heavier nuclei. The process is called nucleosynthesis.