- protons
- electrons
- neutrons
Relative mass of:
- Proton: 1
- Neutron: 1
- Electron 1/1840
Relative electric charge of:
- Proton: +1
- Neutron: 0
- Electron: -1
Protons and Neutrons make up the nucleus of an atom.
Electrons move around the nucleus in the electron shells.
The number of protons = number of electrons
Proton number is the number of protons in the atom.
Nucleon number (mass number) = Number of protons + number of neutrons.
Nucleon number
Symbol of element.
Proton number
For the first 20 elements, the electron configuration is 2, 8, 8.
Isotopes:
Isotopes are atoms of the same element with same number of protons but different number of neutrons. Isotopes of the same element have the same chemical properties but slight difference in their physical properties.
Relative Atomic Mass: The average mass of one atom of an element as compared to 1/12 of the mass of a carbon-12 atom.
Relative molecular Mass: The average mass of a molecule of the substance (element or compound) as compared to 1/12 of a carbon-12 atom.
Atoms form ions -> achieve stable electronic structure. Lose or gain electrons from/into outermost shell.
Stable electronic structure/configuration: duplet, octet structure.
How does ions bond?
Metals lose electrons, form positive ion. Non-metals gain electrons, form negative ion. Positive and negative attract forms ionic bond.
Structure of ionic compounds - giant lattice structure, strong electrostatic forces. strong ionic bonds.
Properties of ionic compounds - high melting point. (break strong ionic bonds)
-soluble in water, insoluble in organic compounds. (water molecules break down ionic compounds
-do not conduct electricity in solid form but conduct electricity in molten/aqueous form.
Structure of convalent substances- small molecules, weak intermolecular forces of attraction, little energy needed to break down.
Properties of convalent substances-low melting & boiling point, insoluble in water, soluble in organic solvents. do not conduct electricity
An acid is a compound that produces hydrogen ions when dissolved in water. Hydrogen responsible for all properties.
It is sour, pH value less than 7, blue litmus paper to red, good electrical conductor because of mobile ions.
Reactions: Acid + reactive metal -> salt + hydrogen (extinguished with a 'pop' sound)
Acid + carbonate -> salt + water + carbon dioxide (bubble through gas, white precipitate, calcium carbonate)
Acid + alkali -> salt + water. (neutralization)
An alkali is a compound that dissolve in water, produce hydroxide ions. Hydroxide ions responsible for alkaline properties.
Examples are calcium carbonate that reduces the acidity of the soil.
It is bitter and soapy, pH value of more than 7, turns red litmus paper into blue, strong alkalis are corrosive, they are good electrical conductors because of the mobile ions.
Universal indicator tells us how acidic/alkaline a substance is.
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