Why does my revision end in such failure?Watch
§ All elements in the same group in the periodic table have similar chemical properties.
§ This is because their atoms have the same number of electrons in their highest occupied energy level.
§ Elements in the periodic table are arranged to their atomic number.
§ An atom overall electrical charge is zero because the number of protons and electrons are equal and charges are equal and opposite.
§ Group 1 elements = reactive = alkali metals.
§ Group 0 elements = not reactive = noble gases.
§ Group 1 elements: lithium, sodium and potassium all react vigorously with water and produce metal hydroxides + hydrogen.
§ Metal + water = metal hydroxides + hydrogen.
§ Group 0 elements are not reactive because they have the stable arrangement of electrons. Outermost shells are full.
§ Covalent bonds form when an atom shares one or more pairs of their electrons.
§ Metals which lose one or more pairs of their electrons form positively charged ions.
§ Non- metals which gain electrons form negatively charged ions.
§ All metals react with other elements by losing their outermost electrons and forming ‘positively charged ions.’
§ Group 1 elements: lithium, sodium, potassium, rubidium, caesium and francium all just have 1 electron in their outermost orbitals. So they are reactive of all metals as this 1 electron is very easily lost.
§ Atoms with an incomplete outer electron shell are unstable. By either gaining or losing electrons atoms can obtain a full outer electron shell.
§ Atoms which lose one or more pairs of their electrons have more protons than electrons. This means that the atoms have obtained a full outer electron shell by the removal of electrons to form a positive ion.
§ Atoms with a nearly empty outer electron shell will lose electrons to obtain a full outer electron shell.
§ Compounds formed from metals or non-metals consist of ions.
§ Electrons always occupy the lowest energy level first.
§ Electrons are in a particular energy level.
§ Atoms have a small, central nucleus composed of 2 subatomic particles = protons + neutrons.
§ Around the nucleus there are electrons which carry a negative charge and are in an orbit.
§ Protons and electrons have an electrical charge; both have the same size of electrical charge. But protons are positive; electrons are negative and neutrons are neutral.
§ PROTONS = +1
§ ELECTRONS = -1
§ NEUTRONS = 0.
§ Ionic bonds = transfer of electrons = metals and non- metals only.
§ Elements in a period have the same occupied energy levels or shells.
§ SIMILARITY BETWEEN ELEMENTS IN SAME GROUP IN PERIODIC TABLE:
§ Same number of electrons in the highest occupied energy level.
§ DIFFERENCE BETWEEN ELEMENTS IN SAME GROUP IN PERIODIC TABLE:
§ Number of shells increase as you move down in the groups.
§ Covalent bonds form because an atom of a non-metal would want to share its electrons with an atom of a different non-metal, as both of these non-metals would want to complete their outer shell by the shared pair of electrons.
§ Ionic bonds form because an atom of a metal would want to lose its electrons in its outermost orbital to obtain a full outer electron shell; the atom of the metal then becomes a positive ion as of this result. The atom of the metal does this by transferring its electrons from its outer shell to an atom of a non-metal which needs to gain electrons to complete its outer shell; the atom of the non-metal then becomes a negative ion as of this result.
§ Electrons always occupy the lowest energy level first, the remaining electrons then go and occupy the higher energy levels.
§ Innermost shells are the lowest energy level.
§ Outer shells have the higher energy levels
§ The number of protons determines the atom’s identity.
§ The number of electrons determines the charge of the element.
§ The atomic weight is the average mass of an naturally occurring atom, an isotope and taking account of neutrons in each isotope.