C3 Atoms, elements and compounds(Benjamin) (Elements, compounds and…
C3 Atoms, elements and compounds(Benjamin)
Elements, compounds and mixtures
Physical properties — typical physical properties of a substance include odor, color,
volume, state, density, melting point, and boiling point.
Chemical properties — refer to its ability to form new substances.
Physical changes — involve a change in one or more physical properties, but new changes in the fundamental components that make up the substance.
Chemical changes — involve a change in the fundamental components of the
substance: a given substance changes into a different substance or substances.
Chemical changes are called reactions
Molecules and covalent bonds
When two non-metal atoms react together, both need to gain electrons to achieve stable outer shells. They manage this by sharing electrons.
Nitrogen (N2), Ethene (C2H4), Methanol (CH3OH), Carbon dioxide (CO2), Hydrogen (H2), Chlorine (Cl2), Water (H2O), Methane (CH4), Ammonia (NH3), Hydrogen chloride (HCl)
Ionic compounds has strong ionic bonds attractive forces
Covalent compounds has strong force between atoms and weak force between molecules
Both diamond and graphite are made only of carbon atoms. So diamond and graphite are allotropes of carbon – two
forms of the same element.
Ions and ionic bounds
Outer shell 2 or 8 electrons
An atom becomes an ion when it lose or gain electrons.
An atom is a charged particle. It is charged because it has an unequal numbers of protonsand electrons
Ionic bonds are the strong electrostatic attraction between cations and anions
In an ionic compound, the cations and anions are packed together in a way to maximize the attractions.
Lattice structure of ionic compounds: regular arrangement of
alternating positive and negative ions.
Atomic structure and the periodic table
Nucleon number(mass), proton number, symbol
Number of neutrons =Nucleon number-proton number
Electron number= Number of protons
Isotopes are atoms of the same element which have the same proton number but a different neuton number.
Physical and chemical changes