Looking for a Tutor Near You?

Post Learning Requirement »
x

Choose Country Code

x

Direction

x

Ask a Question

x

x
x
For better view click here
x
Hire a Tutor
DISCOVER

The Periodic Table

Loading...

Published in: Chemistry
1,799 Views

This is a presentation to know about the features of the Modern Periodic Table and some of trends within the periodic table especially in regard to the reactivity of elements in Groups and periods

Devendra R / Mumbai

20 years of teaching experience

Qualification: B.Sc. PGDMM, DORM - Operations Research,

Teaches: Biology, Chemistry, Mathematics, Physics, Business English, Corporate Communication, Effective Communication, Spoken English

Contact this Tutor
  1. Trends within the periodic table Elements within different groups within the periodic table have different physical and chemical properties. This determines the kinds of reactions these elements have. Different groups also show different trends, in terms of reactivity, as you move down a group. This can also determine how violently a reaction occurs - or whether it happens at all. Group 1 Elements The elements in group 1 are called the alkali metals. They belong to Cl Ar Fe co As Se At Rn the left-hand column in the periodic table. They are very reactive and must be stored in oil to avoid contact with air or water. Li Be Mg Ba Ra sc Y La Ac V Cr cu Zr 3 B In 4 c Si Ge 5 7 F ZIT Cd N P Sn Sb Te O s Pd Pt Group 1 metals Periodic table Group 1 The alkali metals are soft, reactive metals. They react vigorously with water and become more reactive as you go down the group. Common properties The alkali metals have the following properties in common: they are very soft and can be cut easily with a knife they have low densities (lithium, sodium and potassium will float on water)
  2. they react quickly with water - producing hydroxides and hydrogen gas their hydroxides dissolve in water to form alkaline solutions In general: group 1 metal + water group 1 metal hydroxide + hydrogen 2M(s) + 2H20(I) 2MOH(aq) + H2(g) (M stands for the symbol of a Group 1 metal) Physical and chemical trends in Group 1 Melting and boiling points The alkali metals all have low melting points and boiling points compared to other metals. The melting points and boiling points decrease as you go down the group. Reactivity As you go down the group, the metals become more reactive. Lithium (at the top) is the least reactive, while francium (which is at the bottom) is the most reactive. You will probably see lithium, sodium and potassium at school, but rubidium and caesium are considered to be too reactive to use in the classroom. Francium isradioactive and very rare - there are only a few grams of it in the whole of the Earth's crust at any time. Reactions Group 1 metals react with non-metals to form ionic compounds. In these reactions, the metal atom loses its outer electron and becomes a metal ion with a charge of +1. The ionic compounds produced are white solids which form colourless solutions when they dissolve. For example, sodium reacts vigorously with chlorine: sodium + chlorine sodium chloride 2Na(s) + c12(g) 2NaCI(s)
  3. Sodium atom Sodium ion Chlorine atom Chloride ion In the formation of sodium chloride, the electron from the highest energy level of a sodium atom transfers to the highest energy level of a chlorine atom Sodium burns in oxygen to form a metal oxide: sodium + oxygen —i sodium oxide 4Na(s) + 02(g) 2Na20(s) The transition metals The elements in the centre of the periodic table - between groups 2 and 3 - are called the transition elements. They are all metals. They include most of the commonly-used metals, such as iron, copper, silver and gold.
  4. 2 Transition metals Periodic table transition metals 1 Li Be Na Mg Cl Ar As Se At Rn 3 B Al * In 4 c Si Ge 5 N P Sn SD Te 6 O s 7 F He Ne Comparing the properties of the transition elements with the Group 1 elements Melting points Reactivity Strength Density Group 1 elements Low High (react vigorously with water or oxygen) Soft or liquid so cannot withstand force Low Compounds White or colourless Transition elements High (except mercury, which is liquid at room temperature) Low (do not react so vigorously with water or oxygen) Strong and hard Coloured Check you have remembered the properties of transition metals with this activity: Chemical Reactions Most transition metals form coloured compounds.
  5. Itan Coe.ait ehloride Transition metal compounds Copper outphat• Potassium Many transition metals act as catalysts in useful processes. For example, iron is the catalyst used catalyst in the Haber process when Making ammonia. hydrogen + nitrogen ammonia 3H2(g) + N2(g) 2NH3(g) Many transition elements form ions with different charges. For example, iron forms iron(ll) ions, Fe2+, and iron(lll) ions, Fe3+. This means that iron oxide can exist in two forms, iron(ll) oxide, FeO, and iron(lll) oxide, Fe203. Group 7 elements The elements in Group 7 are called the halogens. They belong to the column second from the right in the periodic table. The halogens are all toxic, but this can be a useful property. Chlorine is used tosteri/ise drinking water and water in swimming pools. Iodine is used inantiseptics to treat wounds.
  6. 1 Li Be Na Mg K Fe co As Se Sn SD 2 Ba 3 B cu 4 c Ge 5 N 6 7 He Kr sc Y v Zr Cd w Re Pt Group 7 halogens Periodic table Group 7 Common properties The halogens have the following properties in they are non-metals they have low melting and low boiling points they are brittle when solid common: they are poor conductors of heat and electricity they have coloured vapours their molecules are diatomic (each contain two atoms) - eg chlorine, C12 Physical and Chemical trends in Group 7 Melting point and boiling point The halogens have low melting points and low boiling points. You can see from the graph that fluorine, at the top of Group 7, has the lowest melting point and lowest boiling point in the group. The melting points and boiling points thenincrease as you go down the group.
  7. Fluorine (gas) Chlorine (gas) Bromine (liquid) Iodine (solid) Astatine (solid) 200 -100 o 100 200 Temperature (oc) 300 400 Melting point Boiling point Graph shows the melting and boiling points of halogens Colour The halogens become darker as you go down the group. Fluorine is very pale yellow, chlorine is yellow-green and bromine is red-brown. Iodine crystals are shiny purple-black but easily turn into a dark purple vapour when they are warmed up. Reactivity The halogens become less reactive as you more down the group. Fluorine (at the top of the group) is the most reactive, while astatine (at the bottom) is the least reactive. Reactions Halogens react with metals to form ionic compounds. In these reactions, the halogen atoms each gain one electron to form ions with a charge of -1. Displacement reactions in the halogens Ha/oqens react with metals to form ionic compounds, which dissolve in water. The reacting of the halogens also decreases as you move down the group. These two principles can be used to explain displacement reactions. In these reactions, a more reactive halogen can displace a less reactive halogen from anaqueous solution of its salt. For example, chlorine is more reactive than bromine, so it can displace bromine from bromide compounds: chlorine + sodium bromide sodium chloride + bromine C12(g) + 2NaBr(aq) 2NaCl(aq) + Br2(aq)
  8. Sodium bromide solution Chlorine gas Mixture of sodium chloride solution and bromine A displacement reaction You can see that the Cl and Br have 'swapped places', forming sodium chloride and bromine (which turns the mixture brown). Reactivity series If you test different combinations of the halogens and their salts you can work out a reactivity series for the halogens. The most reactive halogen displaces all the other halogens from solutions of their salts, while the least reactive halogen is always displaced. It works just the same whether you use a sodium salt or a potassium salt. Test your understanding using this animation in which chlorine, bromine and iodine are added to various halogen salts. Note carefully the products which are present in the test tube after each reaction. Trends in reactivity The reactivity of an element depends on how easily its atoms lose or gaine/ectrons. Remember that only the electrons in the highest occupied energy level (outer shell) of an atom are used in bonding. Metals Metal atoms lose electrons when they react with non-metals. For example, elements in Group 1 lose the electron from their highest occupied energy level (outer shell) to form ions with a +1 charge.
  9. As you go down the group, the number of occupied energy levels (filled shells) increases. The higher the energy level of the outer electrons, the greater the distance from the nucleus, and the more easily electrons are lost. This is why elements in Group 1 become more reactive as you go down the group. Non-metals Non-metal atoms gain electrons when they react with metals. For example, elements in Group 7 gain one electron into their highest occupied energy level (outer shell) to form ions with a -1 charge. As you go down the group, the number of occupied energy levels (filled shells) increases. The higher the energy level of the outer electrons, the greater the distance from the nucleus, and the less easily electrons are gained. This is why elements in Group 7 become less reactive as you go down the group. Large force of attraction makes it harder for lithium to lose its outer shell electron, than for other alkali metals, O Lithium atom Large force of attraction makes it easier for fluorine to gain an extra electron in its outer shell, than it is for other halogens. O Fluorine atom F The electron from the second energy level of a lithium atom transfers to the second energy level of a fluorine atom. This creates a positively charged lithium ion and a negatively charged fluoride ion
  10. Greater distance between nucleus and outer shell means less attraction so it is easier to lose the outer electron. Potassium atom Greater distance between nucleus and outer shell means less attraction so it is harder to gain an extra electron. Chlorine atom The electron from the fourth energy level of a potassium atom transfers to the third energy level of a chlorine atom. This creates a positively charged potassium ion and a negatively charged chloride ion

Need a Tutor or Coaching Class?

Post an enquiry and get instant responses from qualified and experienced tutors.

Post Requirement

Related Study Notes

Upload Study Notes

If you have your own Study Notes which you think can benefit others, please upload on LearnPick. For each approved Study Note you will get 100 Credit Points and 100 Activity Score which will increase your profile visibility.

Upload Now
Home > Study Notes > The Periodic Table