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2. • Matter is anything that takes up space and
has mass.
•All matter is made of atoms
•Atoms are the building blocks of matter
•E.G: bricks are the building blocks of houses.

3. •Democritus thought that atoms are tiny,
uncuttable, solid particles that are surrounded
by empty space and constantly moving at
random.
•A Greek philospher Democritus firstly gave
idea of atom.

4. All matter is made up of atoms.
Each element has different atoms.
Atoms can engage in a chemical reactions.
Atoms can neither be created nor be
destroyed, Atoms are indivisible.
JHON DALTON BELONGS TO ENGLAND.

5. •Atom has a positively charged central part
nucleus
•Electrons are distributed around nucleus
Ernest Rutherford Mass of an atom is
concentrated at nucleus
•Compared with total volume_ of an atom, the
volume of O —nucleus is meager

6. •Nucleus - center of the atom of Protons and Neutrons
• Proton Has a positive (+VE) charge
• *Determines the atomic number *inside the nucleus
•Neutron has no (0) charge *inside the nucleus
•'Electron *Has a negative (-) charge *outside the nucleus
Electrons are in specific energy levels called shell of
matter.
•E.G: bricks are the building blocks of houses.

7. •The number of proton in an atom is equal to
number of electrons revolving around it.

8. •Although electrons and protons in an atom have charges,
• but atom as a whole has no charge.
• In an atom, the number of protons is equal to the number of
electrons.
• As a result, the total positive charge of protons balances the
total negative charge of electrons.
• Because of it, the atom is neutral.

9. •The atomic number of an atom is equal to the number of
protons in the nucleus of an atom.
atomic number=number of protons
Z=number of protons
•It is represented by ‘Z’

10. •The mass number is defined as the total number of protons
and neutrons in an atom.
•It can be calculated by adding the number of neutrons and
the number of protons (atomic number) together.
•It is denoted by ‘A’
Mass number=number of neutrons+number of protons
A=number of neutrons+Z

15. A=
Z=