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Physical and Chemical Properties of Period 3 Elements
Transcript of Physical and Chemical Properties of Period 3 Elements
They represent the most straightforward trend in properties.
As the atomic number of the elements increases across a period, the trend is from metallic to a non-metallic character. For Example... Ionization energies increase across the period,because the increase in effective nuclear charge causes an increase in the attraction between the outer electrons and the nucleus. This also makes the electrons more difficult to remove. Metals have a smaller electronegativity than 1.7 and non metals greater than 2.4.
As the size of an atom decreases the electronegativity increases; so the value increases across a period and decreases down a group.
The Melting point of elements across period three, gradually rises with increasing atomic number, until silicon after which they fall dramatically. Melting and boiling points rise across the three metals because of the increasing strength of the metallic bonds. The number of electrons which each atom can contribute to the delocalised "sea of electrons" increase.
The atoms also get smaller and have more protons as you go from sodium to magnesium to aluminum.
The attractions and therefore the melting and boiling points increase because the nuclei of the atoms are getting more positively charged. Silicon: silicon is a giant covalent structure, formed like a diamond, where the atoms are bonded covalently. Each atom is bonded to four other silicon atoms. Breaking all these bonds takes a great amount of energy and that's why silicon has the highest melting point of 1410°C.
Phosphorus, Sulphur and Chlorine are simple covalent molecules while Argon is held together simply by dispersion forces and that is why argon has a very low melting point. The atomic radius is the distance from the nucleus to the outermost electron. In period 3 the atomic radii decreases across the period, as the atomic number increases, the increase in nuclear charge pulls all electrons closer to the nucleus. The size of an atom has an influence on its ionization energy which is a measure of the attraction between the nucleus and the outer electrons Across the period, ions contain the same number of electrons(isoelectornic) but an increasing number of protons, so the ionic radius decreases. This is due to the increase in nuclear charge with the atomic number across the period. Ionization Energy Cont. The first ionization energy increases as the valence electron becomes closer to the nucleus. This is true for all the period 3 elements except for the two “dips” in the group 3 and 4 elements aluminum and sulphur.
The dip in these two elements have given evidence that there are sub-levels called orbitals, because this is where some electrons are found thus needing less ionization energy as they will not be as close to the nucleus as they would be if there weren't any sub-levels. Chemical Properties of Period 3 Elements Reactions with Oxygen Physical Properties of Period 3 Elements :) Reactions with Water and Acid-Base characteristics of the oxides All period 3 elements except silicon and chlorine react directly with oxygen to form oxides.
There is a full range of oxides represeting all the common oxidation states of the elements concerned.
As you might expect, the properties of the oxides change steadily across the period as the atomic number increases.
Sodium, magnesium and aluminum oxides Silicon Dioxide (Silica) The oxides of Sulphur The oxides of chlroine The oxides of metals are predominantly ionic. The oxide of the metalloid silicon is essentially covalent. Silicon dioxide has a giant covalent structure. Sulphur dioxide exists as individual molecules The oxides of chlorine are highly reactive and unstable. They exist as seperate molecules, and therefore have low melting points and exist as gases at room temperature and pressure. As the atomic number of the elements increases across Period 3 from sodium to chlorine, there is a clear trend in the acid-base character of the oxides. The oxides of the metals on the left-hand side of the period are basic, and the oxides of the non-metals on the right-hand side of the period are acidic. Sodium oxide Magnesium Oxide Aluminum Oxide
Silica( Silicon dioxide) The oxides of Phosphorus The oxides of Sulphur The oxides of Chlorine Sodium oxide is a white solid. It reacts with water to give strongly basic aqueous sodium hydroxide. The oxide reacts vigorously with acids to produce an aqueous solution of salt. Therefore it is a basic oxide. (PH 14) Magnesium oxide is a white power which is only slightly soluble in water. The aqueous solution is weakly basic with a PH of approx. 10. The oxide reacts readily with acids to produce a solution of salt. Also a basic oxide. Aluminum is a white solid, which is very insoluble in water. It acts as base when it reacts with excess acid and the hydrated oxide acts as an acid when it reacts with excess aqueous sodium hydroxide to form a complex ion, known as the aluminate ion. Therefore, it has properties of both a basic and acidic oxide.
It is an amphoteric oxide. Highly insoluble with water. Only reacts with highly concentrated alkali or at a high temperature. Phosphorus oxide reacts with water to form aqueous phosphoric acid (PH 1) Sulphur dioxide is a gas with moderate solubility in water, forming an aqueous solution of sulphurous acid. Sulphuric acid is a strong acid and the aqueous solution has a PH close to 0. The chemical properties of the chlorine oxides are dominated by their tendency to explode.