Much of the mass of an atom is concentrated in its nucleus. the nucleus contains , and the outer part of the atom contains

Nucleus contain protons and neutrons while outer part contain electrons.

Explanation:

Atoms are the fundamental unit of matter. Every thing in the universe that occupy space and have mass is called matter. we can say that every matter is composed of atoms. while the atom is composed of subatomic particles called electron proton and neutron.

Subatomic particles       Relative charge       Relative mass

Proton                                 +1                              1

Neutron                                0                             1

Electron                                -1                           0.0005

Electron:

The electron is subatomic particle that revolve around outside the nucleus and has negligible mass. It has a negative charge.

Symbol = e⁻

Mass= 9.10938356×10⁻³¹ Kg

electrical charge on electron= -1.6022 × 10⁻¹⁹ C

It was discovered by j. j. Thomson in 1897 during the study of cathode ray properties.

Proton and Neutron:

An atom consist of positively charged central core (nucleus) that is made up of Proton and neutron.  Proton has positive charge while neutron is electrically neutral. Proton is discovered by Rutherford while neutron is discovered by James Chadwick in 1932.

Symbol of proton= P⁺  

electrical charge on proton= +1.6022 × 10⁻¹⁹ C

Mass of proton=1.672623×10⁻²⁷ Kg

Symbol of neutron= n⁰

Mass of neutron=1.674929×10⁻²⁷ Kg

electrical charge on neutron= 0

i think is conclusions.i think so