KS4 Chemistry The Periodic Table

Atomic number, charge and electrons Atoms contain equal numbers of protons and electrons. This means that atoms are neutral. What is the charge of a fluorine atom? 9 protons = +9 9 electrons = -9 10 neutrons = 0 Total charge = 0 What links atomic number and the number of electrons? atomic number = the number of electrons in an atom

Mendeleev and the periodic table Mendeleev created the first modern periodic table by grouping together elements with similar properties.

Atomic number and patterns of behaviour If the elements are arranged in order of increasing atomic number, patterns in their properties can be seen. reactive gases reactive metals H He Li Be B C N O F Ne Na Mg Al Si P S Cl Ar K unreactive gases

Positions of similar elements Compare the positions of similar elements: reactive gases reactive metals H He Li Be B C N O F Ne Na Mg Al Si P S Cl Ar K unreactive gases How many elements from one reactive gas to the next? 8 How many elements from one reactive metal to the next? 8 How many elements from one unreactive gas to the next? 8

Arranging elements Divide the elements at set intervals into separate rows: cut here cut here cut here H He Li Be B C N O F Ne Na Mg Al Si P S Cl Ar K Arrange these rows so elements with matching properties are together: H He Li Be B C N O F Ne Na Mg Al Si P S Cl Ar K

Arranging elements into columns When elements are arranged according to their properties what patterns do you see? hydrogen is a special case H He Li Be B C N O F Ne Na Mg Al Si P S Cl Ar K reactive gases unreactive gases reactive metals Similar elements go into the same columns. Hydrogen is an exception – it is best positioned above the reactive metals.

The periodic table …the periodic table Arranging all the elements by their atomic number and their properties led to the creation of… …the periodic table H He Li Be B C N O F Ne Na Mg Al Si P S Cl Ar K Ca Sc Ti V Cr Mn Fe Co Ni Cu Zn Ga Ge As Se Br Kr Rb Sr Y Zr Nb Mo Tc Ru Rh Pd Ag Cd In Sn Sb Te I Xe Cs Ba La Hf Ta W Re Os Ir Pt Au Hg Tl Pb Bi Po At Rn Fr Ra Ac Rf Db Sg Bh Hs Mt Ds Rg ?

Missing elements! In this periodic table the symbols are replaced by atomic numbers. Some of the numbers are missing – where? Two more rows of elements fit here. 87 88 89 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 55 56 57 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 37 38 39 40 41 42 43 44 45 46 47 49 50 51 52 53 54 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 11 12 13 14 15 16 17 18 3 4 5 6 7 8 9 10 1 2 They are called the lanthanides and actinides and are only shown on some periodic tables.

The elements in the periodic table

Columns of elements What are columns of elements called? 1 2 groups 3 4 5 6 7 Fr Ra Ac Rf Db Sg Bh Hs Mt Ds Rg ? Cs Ba La Hf Ta W Re Os Ir Pt Au Hg Tl Pb Bi Po At Rn Rb Sr Y Zr Nb Mo Tc Ru Rh Pd Ag Cd In Sn Sb Te I Xe K Ca Sc Ti V Cr Mn Fe Co Ni Cu Zn Ga Ge As Se Br Kr Na Mg Al Si P S Cl Ar Li Be B C N O F Ne H He

Rows of elements What are rows of elements called? periods 1 Fr Ra Ac Rf Db Sg Bh Hs Mt Ds Rg ? Cs Ba La Hf Ta W Re Os Ir Pt Au Hg Tl Pb Bi Po At Rn Rb Sr Y Zr Nb Mo Tc Ru Rh Pd Ag Cd In Sn Sb Te I Xe K Ca Sc Ti V Cr Mn Fe Co Ni Cu Zn Ga Ge As Se Br Kr Na Mg Al Si P S Cl Ar Li Be B C N O F Ne H He 2 3 4 5 6 7

Multiple-choice quiz

H He Electrons in period 1 Elements in period 1 only have electrons in the first shell. Why are there only two elements in period 1? 1 2 3 4 5 6 7 H He 1 1 2 The first shell can only hold a maximum of two electrons, so period 1 only includes the elements hydrogen and helium. What is special about the outer shell of helium?

Li Be B C N O F Ne Electrons in period 2 Elements in period 2 all have a complete first shell. What happens to electrons in the second shell in period 2? 1 2 3 4 5 6 7 Li Be B C N O F Ne 2 2,1 2,2 2,3 2,4 2,5 2,6 2,7 2,8 The second shell is completed one electron at a time going across the period from left to right. What is special about the outer shell of neon?

Na Mg Al Si P S Cl Ar Electrons in period 3 Elements in period 3 have complete first and second shells. What happens to electrons in the third shell in period 3? 1 2 3 4 5 6 7 Na Mg Al Si P S Cl Ar 3 2,8,1 2,8,2 2,8,3 2,8,4 2,8,5 2,8,6 2,8,7 2,8,8 The third shell is completed one electron at a time going across the period from left to right. What is special about the outer shell of argon?

Patterns of electron arrangements Consider the electron arrangements of the first 20 elements in the periodic table. 1 2 3 4 5 6 7 1 1 2 2 2,1 2,2 2,3 2,4 2,5 2,6 2,7 2,8 3 2,8,1 2,8,2 2,8,3 2,8,4 2,8,5 2,8,6 2,8,7 2,8,8 4 2,8,8,1 2,8,8,2 What is the pattern of outer shell electrons in a group? What is the pattern of outer shell electrons across a period? What is the pattern of full electron shells in a group?

Groups and periods

What’s the electron arrangement?