Question

list the three subatomic particles that compose atoms.

Essay answers are limited to about 500 words ( 3800 characters maximum, including spaces)

Answer 1

1) Atoms are composed mainly of protons (p), neutrons (n),and electrons(e). protons have (+1) charge, electron have (-1) charge and neutrons (0).Mass number of proton is (1), neutron(1) and electron(0).Mass of proton is (1.00728), Neutron(1.00867), electron (0.00055).

2) The protons and neutrons are closely packed together in the central part of the atom called nucleus .

3) The electrons are in constant , random motion around the nucleus.They are organised into energy levels or shells located different distances from the nucleus.

4) Energy levels and shells mean the same thing.

5) we use numbers to identify the energy levels (1,2,3,4 etc) or letters to identify the shells ( K,L,M,etc).

6) Electrons in higher energy levels tend to have more energy and tend to be located farther away from the nucleus than electrons in lower energy levels.

7) Rules for filling energy levels .

a) The first Electrons in an atom enter the K shell ,up to a maximum of 2.

b) The next Electrons enter the L shell up to a maximum of 8.

8)Atoms that have the same number of protons but different number of neutrons are called isotope.for example- protium (H1) deuterium (H2)and tritium (H3) . these isotopes of hydrogen form naturally in nature.

9) Normally, the number of electrons in an atom equals to the number of protons and the overall charge of the atom is zero.

10) However atoms may gain or lose electrons:

a)if an atom gains electrons .it will have an extra negative charge for each electron gained.

b) if an atom loses electrons,it will have an extra positive charge for each electron lost.

11) The number of protons in an atom is called the atomic number.All atoms of the same elements ALWAYS have the same atomic number.

12) the number of protons plus the number of neutrons in an atom is called the atomic mass or atomic weight.Different isotopes of the same elements will have different atomic weights.