The Nature of Matter

Annotations:

• Atom is the smallest constitution of a matter

1. electrons: an elementary particle consisting of a charge of negative

   Annotations:

   • Electron is the small particle inside an atom, which carrying negative electric charge.
   • Electron has a mass about 1/1836 of that of proton
   • In an atom, if the number of electrons are equal to the number of protons, then the atom is electrically neutral. 
2. Nucleus: the positively charged central portion of an atom that consists of protons and usually neutrons

   Annotations:

   • Nucleus is the center of an atom, which consists positive electric charged protons and neutrons
   1. protons: an elementary particle that carries a positive charge numerically equal to the charge of an electron

      Annotations:

      • The small particles inside nucleus, which carrying positive electric charge
      • A protons with mass approximately to an atom mass unit
   2. neutrons: an uncharged elementary particle that has a mass nearly equal to that of the proton and is present in all known atomic nuclei except the hydrogen nucleus

      Annotations:

      • A small particle inside nucleus, which carrying no net electric charge
      • A neutron has a mass slightly larger than that of protons

Annotations:

• Chemical Bonds hold the atoms in chemical compounds together. The bond is caused by the electronic attraction between opposite charges. 
• There are varies kind of chemical bond, among them, Ionic and covalent bonds are strong bonds. 

1. Ionic Bonds: a chemical bond formed between oppositely charged species because of their mutual electrostatic attraction

   Annotations:

   • Ionic bonds is formed when one or more electrons are transferred from one atom to another. 
   1. Ions: Ions are electrically charged particles formed when atoms lose or gain electrons.

      Annotations:

      • In an atom, if the number of electrons are equal to the number of protons, then the atom is electrically neutral. Otherwise, if the atom contains more or fewer electrons than protons, then the atom is overall electrically negative or positive, it becomes an ions
2. Covalent Bonds: a chemical bond formed between atoms by the sharing of electrons

   Annotations:

   • When electrons are shared by atoms instead of being transferred, in this case, the moving electrons travel about the nuclei of both atoms, it is called a covalent bond
   1. molecules: The smallest unit of an element or compound, made up of two or more atoms held together by strong chemical bond.

      Annotations:

      • The molecule is the smallest unit of most compounds

1. Isotopes: any of two or more species of atoms of a chemical element with the same atomic number and nearly identical chemical behavior but with differing atomic mass or mass number and different physical properties 2

   Annotations:

   • Isotopes are atoms of the same element, which means with the same number of protons in the nucleus, but  the number of neutrons in the nucleus is different
   • Isotopes are atoms with the same atomic number, but different mass number
2. Element: A substance that cannot be decomposed into simpler substances by chemical means, and is made up of atoms all with identical number of protons

   Annotations:

   • a pure substance which contains single type of atom with specific atomic number
   • There are 118 known elements as shown in the period table