ATOMS ARE THE smallest individual parts of an element.They are tiny, with diameters in the order of one ten -thousand - millionth of a meter .Two or more atoms join together (bond) to form a molecule of a substance known as a compound .For example , when atoms of the elements hydrogen and fluorine join together ,they form a compound hydrogen fluoride .
So molecules are the smallest individual parts of a compound .
Atoms themselves are not indivisible they posses an internal structure .At their centre is a dense nucleus , consisting of protons ,which have a positive electric charge and neutrons , which are uncharged .Around the nucleus are the negatively charged electrons .It is the electrons that give a substance most of its physical and chemical properties.They do not follow definite paths around the nucleus .Instead , electrons are said to be found within certain regions, called orbitals.These are arranged around the nucleus in "shells",each containing electrons of a particular energy .For example , the first shell (1) can hold up to two electron ,in a so called s- orbital (1s).The second shell(2) can hold up to eight electrons ,in s-orbital (2s) and p-orbital(2p).If an atom loses an electron, it become a positive ion (cation).If an electron is gained an atom becomes a negative ion (anion).
Ions of positive charges will attract and join together , in a type of bonding known as ionic bonding.In covalent bonding , the atoms bond by sharing their electrons in what become molecular orbital.
So molecules are the smallest individual parts of a compound .
Atoms themselves are not indivisible they posses an internal structure .At their centre is a dense nucleus , consisting of protons ,which have a positive electric charge and neutrons , which are uncharged .Around the nucleus are the negatively charged electrons .It is the electrons that give a substance most of its physical and chemical properties.They do not follow definite paths around the nucleus .Instead , electrons are said to be found within certain regions, called orbitals.These are arranged around the nucleus in "shells",each containing electrons of a particular energy .For example , the first shell (1) can hold up to two electron ,in a so called s- orbital (1s).The second shell(2) can hold up to eight electrons ,in s-orbital (2s) and p-orbital(2p).If an atom loses an electron, it become a positive ion (cation).If an electron is gained an atom becomes a negative ion (anion).
Ions of positive charges will attract and join together , in a type of bonding known as ionic bonding.In covalent bonding , the atoms bond by sharing their electrons in what become molecular orbital.
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