The Periodic Table - Topic 1 Flashcards
What is the periodic table?
a table that contains all known elements (approx. 100)
How many elements occur naturally?
92
How are elements represented?
by their symbols
How are elements arranged in the Periodic Table?
- Elements are arranged in order of increasing atomic number in rows called periods
- Elements with similar chemical properties are placed in the same vertical columns called groups
What is the number of electron energy levels (shells) of an element on the Periodic Table the same as?
the period number of the element in the Periodic Table
What is the number of electrons in the outer energy level (shell) the same as?
the group number of the element in the Periodic Table
What happens to elements as you go down Group 2 in the Periodic Table?
they get more reactive
What do elements in the same group share?
elements in the same group share similar chemical properties
Group 2 Metals: What is more reactive magnesium or calcium?
calcium is more reactive than magnesium
acid + metal –>
salt + hydrogen
acid + metal carbonate –>
salt + water + carbon dioxide
water + metal –>
metal hydroxide + hydrogen
What is the test for hydrogen?
To test for the hydrogen we placed a lit splint at the neck of the test tube and if a squeaky pop sound was made then hydrogen was present
Periodic table:
table of elements arranged in increasing atomic number and such that elements with similar properties are grouped together (in the same column)
Group:
- a column of the periodic table
- elements of the same groups have similar chemical properties
Period:
- a row of the periodic table
- elements of the same row have the same number of shells
How did Mendeleev arrange the elements?
- in 1869 Russian scientist Dimitri Mendeleev arranged the elements in a periodic table using the chemical properties of these elements and their compounds
- ordered his table in terms of atomic mass but not always strictly i.e. he would change the order based on atomic weight
- he left gaps in his table where elements didn’t match certain properties
- he swapped the order of some elements
Examples where Mendeleev switched the order of two elements:
- iodine (I - 127) and tellurium (Te - 128)
How did Mendeleev justify his change of leaving gaps in the table and swapping some elements?
- as the reactivities wouldn’t match up if he didn’t leave gaps
- to make patterns fit (to keep families together)
- that they would be occupied by undiscovered elements
- used his table to predict the existence and properties of some elements that hadnt been discovered as he realised elements with similar properties belonged in the same groups in the periodic table so was able to leave gaps and place the discovered elements where they fit best
- elements with properties predicted by Mendeleev were later discovered and filled the gaps
How did Mendeleev’s predictions of the properties of Eka-aluminium compare to the properties of gallium?
- properties very close
- density is an especially good agreement of chemical and physical properties
What effect did the discovery of gallium have on the development of the Periodic table?
- it provided evidence that Mendeleev’s idea to leave gaps in the periodic table was correct - table became accepted by mosts scientists
3 important differences between Mendeleev’s table and the modern periodic table:
- his periodic table was ordered in terms of atomic mass and now the modern periodic table is ordered in terms of atomic number
- lanthanoid, actinides and transition metals added - more groups addes
- addition of noble gases - no Group 0 in Mendeleev’s table
Why did Mendeleev think that he had arranged elements in order of increasing relative mass and why was this not always true?
- not always true because of the relative abundance of isotopes of some pairs of elements in the periodic table
- knowledge of isotopes made it possible to explain why the order based on atomic weights was not always correct, because some elements have a higher mass than others when isotopes are taken into account, but a lower one if you only look at one specific isotope
Explain the meaning of atomic number of an element in terms of position in the periodic table and number of protons in the nucleus:
- Elements are arranged in order of atomic (proton) number (bottom number) and so that elements with similar properties are in columns, known as groups
- Elements in the same group have the same amount of electrons in their outer shell, which gives them similar chemical properties
How are elements in the periodic table arranged?
- Elements are arranged in order of increasing atomic number in periods
- Elements with similar properties are grouped together
What is a group and what do elements in the same group have in common in the Periodic table?
- a group is a column in the periodic table
- elements in the same group have the same number of electrons their outer shells (isoelectronic)
- have similar chemical properties and reactivity
What is a period what do elements in the same period have in common?
- period is a row in the periodic table
- elements in a period have the same number of shells
Name for Group 1 elements:
Alkali metals
Name for Group 2 elements:
The Alkaline Earth Metals
Name for Group 7 elements:
Halogens
Name for Group 8/0 elements:
Noble gases
List all the group 1 elements:
- lithium (Li)
- sodium (Na)
- potassium (K)
- rubidium (Rb)
- cesium (Cs)
- francium (Fr)
List all the group 2 elements:
- Beryllium (Be)
- Strontium (Sr)
- radium (Ra)
- Magnesium (Mg)
- Barium (Ba)
List all the group 7 elements:
- fluorine (F)
- chlorine (Cl)
- bromine (Br)
- iodine (I)
- astatine (At)
List all the elements in the first row of the transition metals:
- Scandium (Sc)
- Titanium (Ti)
- Vanadium (V)
- Chromium (Cr)
- Manganese (Mn)
- Iron (Fe)
- Cobalt (Co)
- Nickel (Ni)
- Copper (cu)
- Zinc (Zn)
Compare the properties of titanium and sulphur:
- Titanium
- transition metal in period 4
- 2,8,8,4
- hard, shiny metal
- grey
- lactic structure
- malleable
- metallic
- high mp and bp
- ductile
- dense
- strong
- good conductor of electricity and heat
- Sulphur
- non-metal in period 3, group 6
- 2,8,6
- simple molecular structure
- yellow
- low mp and bp
- brittle
- poor conductor of electricity and heat
How is the charge of ions related to their position on the Periodic Table?
- charge of ions is the same as the group numbers for the first 3 groups
- the charges of the ions are its group number subtract its atomic number (which is the number of electrons the atoms needs to lose to gain a full outer shell)
Why do all ions have the charges they do?
- to gain a full outer shell elements either gain or lose electrons (whichever is easier) giving them they’re charges
- metals lose electrons (cations) and non-metals gain electrons (anions) to gain a full outer shell
Metals and non-metals on the Periodic table:
Metals in the Periodic table:
- elements that react to form positive ions.
- majority of elements are metals.
- found to the left and towards the bottom of the periodic table., because they lose electron(s) in order to form these positive ions, forming an electronic structure that is stable, like that of a noble gas
Non-metals in the Periodic table:
- elements that form negative ions
- found towards the right and top of the periodic table, because they gain electron(s) in order to form these negative ions, forming an electronic structure that is stable, like that of a noble gas
What is the difference between metals oxides and non-metal oxides?
- metal oxides are ionic and dissolve to give alkaline solutions
- metal oxides are coloured solids
- non-metal oxides are normally gases
- non-metals oxides are covalent and dissolve to give acid solutions
How is an elements electronic configuration related to its position on the Periodic table?
- The number of electron energy levels (shells) is the same as the period number of the element in the Periodic Table
- The number of electrons in the outer energy level (shell) is the same as the group number of the element in the Periodic Table
Why did some scientists not accept Mendeleev’s arrangement of elements in his table?
- he had left gaps in his table where no elements fit the correct properties of the space and used them to predict the discovery of elements
- swapped he order of elements - didn’t always strictly order the elements in atomic mass
Who were atoms first suggested by and when?
atoms first suggested by Democritus in approx. 400 BCE
Who was the idea of atoms rediscovered by and when?
idea of atoms re-discovered by John Dalton at start of 1800’s
How did John Dalton arrange elements?
he used clever chemical reactions to arrange different elements in order of their atomic masses
From John Dalton’s model which elements are close to their modern atomic masses?
- gold 190 vs 197
- potassium 42 vs 47
- copper 56 vs 64
From John Dalton’s model which elements have masses which are completely wrong?
- carbon 5 vs 12
- oxygen 7 vs 16
- phosphorous 9 vs 31
What did John Newlands do and when?
- 1864 - he built on John Dalton’s ideas
- also arranged elements in order of mass - notices that properties of every 8th elements seemed similar
- he produced a table to demonstrate his “Law of Octaves”
John Newlands’ Table “Law of Octaves”
What are the modern symbols for the elements “G” and “Bo” (from John Newlands table)?
- Boron (B)
- Beryllium (Be)
In the left hand column of John Newlands which elements have similar properties?
- F, Cl, I, Br
- Co, Ni, Pd, Pt, Ir
Which elements don’t fit within the left hand column of John Newlands column?
the metals (e.g. Co, Ni, Pd, Pt, Ir) do not fit with the non-metals (F, Cl, I, Br)
Why was John Nelwands table not accepted by peers?
- not all elements in the same group had similar properties
- sometimes more than one element occupying the same space
- why order the elements according to a piano?
