In what order were the elements put in the early periodic table?
In order of increasing atomic weight. (now we call it atomic mass)
Write an ionic equation for the reaction of the alkali metal atom
Li → Li+ + e-
Na → Na+ + e-
K → K+ + e-
Rb → Rb+ + e-
Cs → Cs+ + e-
How were the elements put into columns or groups?
Elements with similar properties are in columns, known as groups.
Why was this known as a periodic table?
Periodic means repeats regularly, similar properties occur at regular intervals.
What were Newlands’ octaves?
John Newlands published a table showing that every eighth element had similar properties and could be grouped together.
State the two main problems with the early periodic tables.
They were incomplete, only 56 elements had been found by 1865 for Newlands to octave.The elements were arranged by mass or weight which meant that some atoms did not fit the pattern and were put in the wrong groups.
How did Mendeleev overcome problems with the early periodic tables?
When he made his table, Mendeleev left spaces for elements that were yet to be discovered, famously Ga and Ge, so that the other elements fitted into the right groups.
What did Mendeleev use to sort the elements into groups in his periodic table in 1869?
The elements were still in order of atomic weight. They were put into groups using their properties and the formulae of their compounds.
Explain why scientists thought the periodic table of the elements was a curiosity at first?
The early tables were incomplete, some only worked for the first few elements.
What discovery led to the modern versions of the periodic table?
The discovery of electrons, protons and neutrons early in the twentieth century.
In what order were the elements put in the modern periodic table?
In order of increasing atomic number.
What difference did this make to the modern periodic table?
The elements were placed in the proper groups.
How does this change to the order of the elements link to atomic structure?
The periodic table could be used to work out the electronic structure of the elements as well as the number of protons and neutrons.
How does the electronic structure change across each period in the table?
In period 1 the first shell is filled, in the second period the second shell is filled, etc. e.g. Li- 2.1, Be- 2.2, B- 2.3, C- 2.4.
How does the electronic structure change down each group in the table?
Elements in the same group have the same number of electrons in their highest occupied electron shell (outer shell).
What are the electronic structures of the group 2 metals Be, Mg, Ca?
Be – 2.2 Mg – 2.8.2 Ca – 220.127.116.11 All of the Group 2 metals have two electrons in their outer shells
What information tells you the number of electrons in the outer shell of an element?
The group number. All the Group 1 elements have one electron in their outer shell, all the group 2 elements have 2, etc.
How many electrons does iodine have in total and how many electrons are there in the outer shell?
Iodine has atomic number 53 so it has 53 electrons in total. It is in group 7 so iodine has seven electrons in its outer shell.
Describe the density of the alkali metals, be specific about the first three?
The alkali metals have low density, the first three (Li, Na, K) all float on water
How do the alkali metals react with non-metals?
They react with non-metals to form ionic compounds in which the metal ion carries a charge of +1.
Describe the compounds of the alkali metals with non-metals.
The compounds are white ionic solids that dissolve in water to form colourless solutions
Describe the reaction of the Lithium with water
Lithium floats and fizzes with water, releasing hydrogen gas. It forms lithium hydroxide which dissolves in water to give an alkaline solution that turns UI indicator purple.
Describe the pattern of the reaction of the alkali metals with water
The further down group 1 an element is the more reactive the element; Sodium floats, fizzes and melts. Potassium floats, fizzes, melts and catches fire (lilac fame)
Using M as the alkali metal atom, write an equation for the reaction of an alkali metal with water
2M(s) + 2H2O(l) → 2MOH(aq) + H2(g)
Explain the pattern in reactivity going down the alkali metals.
As you go down the group the atoms get more shells and the single electron in the outer shell is further from the nucleus, so it is less tightly held and more easily lost. The elements need less activation energy to react i.e. they get more reactive
What is the pattern in melting points and boiling points, going down the alkali metals?
The further down the group an element is the lower its melting point and boiling point.
Compare the physical properties of the transition metals with the alkali metals.
Compared with the elements in Gp 1, transition elements have higher melting points (except for mercury) and higher densities. They are stronger and harder.
Compare the chemical properties of the transition metals with the alkali metals.
Compared with the elements in Gp 1, transition elements are much less reactive and so do not react as vigorously with water or oxygen.
Give the three characteristic properties of transition metals.
Many transition elements have ions with different charges; form coloured compounds and are useful as catalysts.
What is the collective name for the group 7 elements?
They are known as the halogens.