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|atomic numbers. The horizontal rows are called periods. All elements in a period have the same number of shells of electrons. Each element across the row has an increment of one outer electron from left to right. The vertical columns are called groups. Elements within the same group all have the same number of electrons in their outer shell. They therefore tend to have similar chemical properties. Elements in the table can be classified as metals, non-metals, or metalloids. Metals have certain properties, which distinguish them from non-metals. These include generally high melting points, a shiny appearance, and good malleability (flatten into sheets), ductility (drawn into wires) and conductivity of electricity and heat. Some elements have both metallic and non-metallic properties. They are known as metalloids.|
Figure 12-26 Periodic Table, Traditional [view large image]
|and is reduced when its valence number decreases. Figure 12-27 shows the valence for some common chemical elements. The value for electronegativity is a number that indicates the relative ability of an element to attract electrons. The rule for forming chemical compounds is to complete the shell by either accepting electrons or to denote depending on which way is easier to achieve. In Figure 12-27 the|
Figure 12-27 Valence
|number of electrons to form a complete shell is two for hydrogen, and eight for carbon and oxygen. Thus oxygen tends to accept two more electrons and has a higher value for electronegativity. Further detail can be found in the topic on Atom.|
|Acids||Dissolve in water and produce H+.
Taste - sour, feel - may sting.
|Bases||Accept acids' H+ such as NaOH and MgO.
Taste - bitter, feel - slippery.
|Alkalis: soluble such as NaOH
Insouble Base: Cu(OH)2
|Salts||Ionic compounds consist of metal and nonmetal ions.
hard and brittle,
hight melting/boiling points,
conduct electricity when dissolved or melted,
may react with water to form neutral, acid or basic solution.
|Insoluble: attraction between ions > with water - PbCl2
Neutral: dissolves into hydrated ions -
Medium: dissolves into metal cations and anions of acid radical - (Na+)2(SO42-)
Acid: dissolves into metal cations, hydrogen and acid radical anions - (Na+)(H+)(CO32-)
Basic: dissolves into metal cations, hydroxyl and acid radical anions - (Zn2+)(OH-)(Cl-)
Double: dissolves into two cations and one anion -
Mixed: dissolves into one cations and two anion -
Complex: dissolves into complex cations or anions -
|Oxides||Consist of two elements, one of which is
oxygen. The oxide group contains the greatest variations of physical properties. Some are hard, some soft. Some have a metallic luster; others are clear and transparent.
|Non-salts: CO, NO, N2O (see general rules)|
Basic: salts with metal oxidation number +1, to +3 - MgO
Amphoteric: salts with oxidation # +2, to +4 - Al2O3
Acid: salts with metal oxidation number +3, to +7 - SiO2
|metal + non-metal||salt||Hg + S HgS|
|basic oxide + acid oxide||salt||MgO + CO2 Mg CO3|
|base + acid||salt||Ca(OH)2 + 2HCl CaCl2 + 2H2O|
|metal + oxygen||basic oxide||2Mg + O2 2MgO|
|non-metal + oxygen||acid oxide||4P + 5O2 2P2O5|
|basic oxide + water||base||Na2O + H2O 2NaOH|
|acid oxide + water||acid||SO3 + H2O H2SO4|
|acid + salt||salt + acid||H2SO4 + BaCl2 BaSO4 + 2HCl|
|acid + metal||salt||6HCl + 2Al 2AlCl3 + 3H2|
|base + salt||salt + base||Ba(OH)2 + K2SO4 BaSO4 + 2KOH|
|base + acid oxide||acid salt||KOH + CO2 KHCO3|
|Many of the most commonly used metals, such as iron and silver, belong to a group called transition metals, found in the middle of the periodic table. They have more than one valence. The compounds that they form are often brightly coloured. Many metals react with water, with dilute acids and with the oxygen in the air. They can be listed in order of how reactive they are. This is known as the reactivity series and is shown in Figure 12-28 with the most reactive on top and the least reactive on the bottom.|
Figure 12-28 Reactivity Series [view large image]