C2 - Periodic Table
- Created by: izz08
- Created on: 14-11-17 20:23
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- C2 - The periodic table
- Development of the periodic table
- The periodic table of elements developed as chemists tried to classify the elements. It arranges them in an order in which similar elements are grouped together
- The periodic table is so named because of the regularly repeating patterns in the properties of elements
- Mendeleev's periodic table left gaps for the unknown elements, which when discovered matched his predictions, and so his table was excepted by the scientific community
- Electronic structures and the periodic table
- The atomic (proton) number of an element determines it position in the periodic table
- The number of electrons in the outermost shell (highest energy level) of an atom determines its chemical properties
- The group number in the periodic table equals the number of electrons in the outermost shell
- The atoms of metals tend to lose electrons, whereas those of non-metals tend to gain electrons
- The noble gases in Group 0 are unreactive because their very stable electron arrangement
- Group 1 - the alkali metals
- The elements in group 1 of the periodic table are called alkali metals
- Their melting points and boiling points decrease going down the group
- The metals all react with water to produce hydrogen and an alkaline solution containing the metal hydroxide
- They form positive ions with a charge of 1+ in reactions to make ionic compounds. Their compounds are usually white or colourless crystals that dissolve in water producing colourless solutions
- The reactivity of the alkali metals increase going down the group
- Explaining trends
- You can explain trends in reactivity as you go down a group in terms f the attraction between electrons in the outermost shell and the nucleus
- The electrostatic attraction depends on: - The distance between the outermost electrons and the nucleus - The number of occupied inner shells of electrons, which provide a shielding affect - The size of the positive charge on the nucleus (called the nuclear charge)
- In deciding how easy it is for atoms to lose or gain electrons from their outermost shell, theses three factors mus be taken into account. The increased nuclear charge , due to extra protons in the nucleus, going down a group is outweighed by the two other factors.
- Therefore electrons are easier for the larger atoms to lose going down a group, and harder for them, too gain going down a group
- Development of the periodic table
- Group 7 - the halogens
- The halogens all form ions with a single negative charge in their ionic compounds with metals
- The halogens form covalent compounds by sharing electrons with other non-metals
- A more reactive halogen can displace a less reactive halogen from a solution of one of its salts.
- Development of the periodic table
- The periodic table of elements developed as chemists tried to classify the elements. It arranges them in an order in which similar elements are grouped together
- The periodic table is so named because of the regularly repeating patterns in the properties of elements
- Mendeleev's periodic table left gaps for the unknown elements, which when discovered matched his predictions, and so his table was excepted by the scientific community
- The reactivity of the halogens decreases going down the group
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